Epidermal Growth Factors (EGF) and Analogs
Definition
Epidermal Growth Factor (EGF) is part of a complex network of growth factors and receptors that together help to modulate the growth of cells. EGF is released by cells, and then is picked up either by the cell itself, stimulating its own growth, or by neighboring cells, stimulating their ability to divide 1.
Related Peptides
Depending on their binding specificities, EGF-related peptides can be subdivided into two classes. The first group of ligands binds to the EGFR (EGF receptors) and includes EGF itself, transforming growth factor (TGF) a, amphiregulin (AR), heparin-binding EGF-like growth factor (HB-EGF), and betacellulin (BTC). Each of these peptides competes with EGF for receptor binding and therefore this family of growth factors is referred to as the EGF agonists. Another family of EGF-related peptides is composed of the neu differentiation factors (NDFs)/heregulins ligands for ErbB-3 and ErbB-4. There are at least 12 different isoforms arising from a single gene by alternative splicing and depending on the sequence of their EGF-like repeat they are classified as either a or ß isoforms. However, despite the large number of NDFs no differences in receptor binding specificities appear to exist: ErbB-3 functions as a low affinity receptor for all NDF isoforms while ErbB-4 serves as a high affinity receptor 2.
Discovery
The discovery of EGF won Stanley Cohen a Nobel Prize in Physiology and Medicine in 1986 and was patented for cosmetic use by Greg Brown in 1989 .
Structural Characteristics EGF is a small mitogenic protein that is thought to be involved in mechanisms such as normal cell growth, oncogenesis, and wound healing. This protein shows both strong sequential and functional homology with human type-alpha transforming growth factor (Htgf-a), which is a competitor for EGF receptor sites. EGF is a small 53 amino acid residue long protein that contains three disulfide briges. The side chains of residues 13 (Tyr), 41 (Arg), and 47 (Leu) are all thought to play an important role in EGF's functionality 3.
Analogs
Three site-directed mutants of human epidermal growth factor, Leu-26-Gly, Leu-47-Ala, and Ile-23-Thr, were examined for their ability to stimulate the protein-tyrosine kinase activity of the epidermal growth factor receptor. The receptor binding affinities of the mutant growth factors were 20- to 50-fold lower, as compared to wild-type growth factor. At saturating concentrations of growth factor, the velocities of the phosphorylation of exogenously added substrate and receptor autophosphorylation were significantly lower with the mutant analogs, suggesting a partial 'uncoupling' of signal transduction. The mutant analogs were shown to compete directly with the binding of wild-type, resulting in a decrease in growth factor-stimulated kinase activity 4. Six mutants of human EGF, which carry single point substitutions within a surface patch proposed to juxtapose the bound receptor, were prepared and characterized for receptor affinity and mitogenicity. Receptor affinities relative to EGF are G12Q > H16D > Y13W > Q43A ˜ H16A ˜ EGF >> L15A. Notably, the reduced receptor affinity of mutant L15A indicates that Leu15 probably contributes substantially to receptor binding whereas unaltered receptor affinities observed for analogs H16A and Q43A indicate that neither His16 nor Gln43 contributes significantly to this interaction. On the other hand, the observed enhanced receptor affinities of analogs G12Q, Y13W and H16D highlight surface loci where additional productive receptor-binding contacts can be introduced. Interestingly, at acidic pH analog H16A reveals substantially greater receptor affinity than that of EGF, a property which may offer enhanced therapeutic utility in acidic environments in vivo 5.
Mode of Action
Receptors on the surface of the cell bind to EGF and relay the signal inside. When the receptor binds to EGF, it is activated by forming a dimer with other receptors. Four similar receptors have been discovered: the EGF receptor and three variants. These may dimerize with themselves, or mix-and-match to form heterodimers with the other types. The set of growth factors that interacts with these receptors is even more varied, with a dozen or so known examples, including EGF, transforming growth factor-a, and a number of neuregulins. The receptor is composed of a single chain with many functional parts. It is found in the cell membrane, with one portion facing out to receive the message and one portion facing inward to relay the message to the cell machinery. The outer portion forms an EGF-binding domain. It is composed of four articulated parts: two globular parts that grip EGF and two rod-shaped linkers that are rigidified by dozens of cysteine amino acids. When this multi-part domain binds to EGF, it changes shape, releasing one of the long, cysteine-rich sections. This allows the receptor to dimerize with other receptors. This brings the two kinase domains close to one another, allowing them to add phosphates to each other and activating the signaling process. Many hormone receptors act by binding to either side of a hormone, with the hormone in the center. The EGF receptor, surprisingly, forms dimers with the growth factors on opposite sides of the dimer, far from the point of contact between the two receptors6.
Functions
The EGFR signaling pathway is one of the most important pathways that regulate growth, survival, proliferation, and differentiation in mammalian cells6. In animal models of acute renal injury, the administration of epidermal growth factor, insulin-like growth factor I (IGF-I), or hepatocyte growth factor accelerates the restoration of kidney function and the normalization of histology post-acute renal injury and reduces mortality. The mechanisms by which the growth factors act in acute renal failure include the stimulation of anabolism, the maintenance of glomerular filtration, and the enhancement of tubular regeneration7.
References
1. Goodsell DS (2003). The molecular perspective: epidermal growth factor. The Oncologist, 8(5):496–497.
2. Beerli RR, Hynes NE (1996). Epidermal growth factor-related peptides activate distinct subsets of erbb receptors and differ in their biological activities. J Biol Chem., 271:6071-6076.
3. Montelione GT, Wuthrich K, Burgess AW, Nice EC, Wagner G, Gibson KD, Scheraga HA (1992). Solution structure of murine epidermal growth factor determined by NMR spectroscopy and refined by energy minimization with restraints. Biochemistry, 31:236-242.
4. Matsunami RK, Campion SR, Niyogi SK, Stevens A (1990). Analogs of human epidermal growth factor which partially inhibit the growth factor-dependent protein-tyrosine kinase activity of the epidermal growth factor receptor. Febs letters, 264(1):105-108.
5. Mullenbach GT, Chiu CY, Gyenes A, Blaney J, Rosenberg S, Marlowe CK, Brown S, Stratton-Thomas J, Montelione GT, George-Nascimento C, Stauber G (1998). Modification of a receptor-binding surface of epidermal growth factor (EGF): analogs with enhanced receptor affinity at low pH or at neutrality. Protein Engineering, 11(6):473–480.
6. Oda K, Matsuoka Y, Funahashi A, Kitano H (2005). A comprehensive pathway map of epidermal growth factor receptor signaling. Molecular Systems Biology, 1:2005.
7. Hammerman MR, Miller SB (1994). Therapeutic use of growth factors in renal failure. Journal of the American Society of Nephrology, 5:1-11.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
Eosinophilotactic Tetrapeptides
Definition
Eosinophilotactic tetrapeptides exhibit peak in vitro chemotactic activity for human eosinophils and rapidly deactivate eosinophils to homologous and other stimuli at concentrations as low as 10 -10 M 1.
Related Peptides
The ECF-A acidic tetrapeptides Val-Gly-Ser-Glu, Ala-Gly-Ser-Glu and the analogue Val-Gly-Asp-Glu are selectively chemotactic for human eosinophils over a narrow dose range. Histamine abrogates the chemotactic properties of the individual tetrapeptides 2.
Discovery
The eosinophil chemotactic factor of anaphylaxis, ECF-A, was discovered in 1971 by Kay et al., as a mediator released during immediate-type hypersensitivity reactions in guinea pig and human lung slices 1.
Structural Characteristics
Two eosinophilotactic tetrapeptides of amino acid sequence Val-Gly-Ser-Glu and Ala-Gly-Ser-Glu were recovered from the extracts in 4-12% overall yield of the low molecular weight peak from Sephadex G-25. Purified eosinophil chemotactic factor of anaphylaxis and the synthetic tetrapeptides were maximally active in a chemotactic chamber, and the activity was dependent on both the NH2 terminal and the COOH-terminal residues. Both natural and synthetic peptides were preferentially chemotactic for eosinophils and rendered them unresponsive to a subsequent stimulus1.
Mode of Action
The chemotactic activity of the tetrapeptide is dependent on both the hydrophobic NH2-terminal residue, which interacts with a hydrophobic domain in the chemotactic receptor, and the highly-charged COOH-terminal residue which is presumed to initiate eosinophil movement by perturbing a polar domain in the same receptor. The spatial requirement for effective interaction with both domains in the receptor is revealed by the lower potency and activity of the condensed tripeptides lacking glycine. The 10-fold greater potency of NH2-terminal tripeptide compared to the amide derivatives of NH2-terminal amino acids in reversibly inhibiting the intact tetrapeptides suggests a role for serine in binding to a portion of the receptor, possibly by hydrogen bonding. The COOH-terminal substituent tripeptide irreversibly suppresses eosinophil chemotaxis by a cell-directed action possibly reflecting its capacity to perturb the polar domain; this effect, resembling de-activation, requires higher concentrations than needed for deactivation by the tetrapeptide 3.
FunctionsECF-A was discovered in 1971 as the mediator that is responsible for most of the eosinophil chemotactic activitv released during anaphylactic reactions. Of the other mediators of immediate hypersensitivity, only histamine stimulates directed migration of eosinophils in vitro; however, its action is transient and lacks apparent in vivo chemotactic activity 4.
References
1. Goetzl EJ, Austen KF (1975). Purification and synthesis of eosinophilotactic tetrapeptides of human lung tissue: Identification as eosinophil chemotactic factor of anaphylaxis (leukocyte chemotaxis/leukocyte deactivation/ anaphylactic mediators/acidic peptides of lung). PNAS., 72(10):4123-4127.
2. Turnbull LW, Evans DP, Kay AB (1977). Human eosinophils, acidic tetrapeptides (ECF-A) and histamine. Interactions in vitro and in vivo. Immunology, 32(1):57-63.
3. Goetzl EJ, Austen KF (1976). Structural determinants of the eosinophil chemotactic activity of the acidic tetrapeptides of Eosinophil Chemotactic Factor of Anaphylaxis. J Exp Med., 144:1424-1437.
4. Goetzl EJ (1976). Modulation of human eosinophil polymorphonuclear leukocyte migration and function. Am J Pathol., 85(2):419-436.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
Enkephalins and Proenkephalins
Definition
Enkephalins are opioid peptides that are found at high levels in the brain and endocrine tissues. The major species of newly appearing enkephalin-containing peptide appears to be the intact precursor, proenkephalin 1.
Related Peptides
Opioid peptides constitute a large group of small proteins that interact with cell membrane receptors similarly to opiate alkaloids, morphine and heroin. Opiate alkaloid derivatives are extensively used for analgesia and anesthesia. The original opioid peptide families are enkephalins, dynorphins, and endorphins. Representative peptides from these three opioid peptide families have been found in the heart. Three different opiate receptors have been cloned and sequenced: mu (µ), delta (d), and kappa (?) 2.
Discovery
Kosterlitz and Hughes discovered enkephalins and endorphins in 1975 3.
Structural Characteristics
The amino acid sequence of methionine-enkephalin (Met-Enk) is tyrosine-glycine-glycine-phenylalanine-methionine. The proenkephalin sequence contains four copies of the pentapeptide Met-Enk, one of leu-enkephalin, and two extended forms of Met-enk (Met-enk-arg6-phe7 and met-enk-arg6-gly7-leu8). Pairs of basic amino acids mark these small peptides for cleavage from the precursor. Proenkephalin is processed by endoproteolytic enyzmes termed prohormone convertases, which recognize and cleave at dibasic amino acid sites. Initial proenkephalin processing starts before transport to the golgi network and are rapid. Later processing requires an acidic environment distal to the golgi network. Proenkephalin has a fast cleavage to peptide B, and slower cleavages yield other intermediate sized products that are cleaved ultimately to the penta to octapeptides. The different molecular-weight end products found in diverse tissues (muscle, neural, endocrine) may be due to variations in the cleavage sequence and local enzymatic conditions for processing 2.
Mode of Action
Pentapeptides Met-Enk and Leu-Enk, the endogenous ligands for the opiate receptor, function as neuromodulators or neurotransmitters. The most prominent action of enkephalins in the mammalian brain is depression of neuronal firing rate and it has been suggested that these peptides are inhibitory transmitters. The response of central neurones to several putative transmitter substances is depressed or enhanced by enkephalins, suggesting a postsynaptic action. It has also been shown that enkephalins suppress the K+-induced release of noradrenaline, dopamine and acetylcholine from rat brain slices, indicating a presynaptic effect. The firing of myenteric neurones in the guinea-pig ileum is inhibited by enkephalins. This inhibition is probably due to a direct postsynaptic action of the enkephalins resulting in a hyperpolarisation of the neuronal membrane 4. To achieve their biological function, enkephalins must be transported from an aqueous phase to the lipid-rich environment of their membrane bound receptor proteins. It is now known that Met-enk acts via three main subtypes of receptors referred to as µ, d and ? - receptors. While the first two receptor subtypes mediate the classic opioid effects of Met-enk, ?-receptors are reported to be involved in the non-opioid actions of the peptide, i.e. the inhibitory effect on the cell growth 5.
Functions
Proenkephalin is a precursor for neuropeptides with a variety of functions in the neuroendocrine and nervous systems. Upon activation, T-helper lymphocytes were found to express high levels of proenkephalin mRNA and to secrete large amounts of the Met-Enk neuropeptide, perhaps indicating an axis by which the immune and nervous systems interact 6. Enkephalins cause antinociception and potentiated morphine analgesia but they also block the development of tolerance and physical dependence. In addition to their central and peripheral antinociceptive function, opioids can modulate immune activity and cell proliferation. Moreover it is known that they have significant role in different physiological processes like cell differentiation and regeneration, inflammation, cancer and angiogenesis and analgesia effects 5.
References
1. Fleminger G, Lahm HW, Udenfriend S (1984).Changes in rat adrenal catecholamines and proenkephalin metabolism after denervation. PNAS., 81(11):3587-3590.
2. Barbara A. Barron. 2000. Cardiac Opioids. Proceedings of the Society for Experimental Biology and Medicine, 224:1-7.
3. Fratta W, Yang HY, Hong J, Costa E (1977). Stability of Met-enkephalin content in brain structures of morphine-dependent or foot shock-stressed rats. Nature, 268(5619):452-453.
4. Wouters W, Den Bercken JV (1979). Hyperpolarisation and depression of slow synaptic inhibition by enkephalin in frog sympathetic ganglion. Nature, 277:53-54.
5. Tsanova A, Dacheva D, Penchev V, Georgiev G, Pajpanova T, Golovinski E, Lalchev Z (2009). Comparative study of the interaction between synthetic methionine-enkephalin and monolayers of zwitterionic and negatively charged phospholipids. Biotechnol & Biotechnol., 23:463-466.
6. Rattner A, Korner M, Rosen H, Baeuerle PA, Citri Y (1991). Nuclear factor Kappa B activates proenkephalin transcription in T lymphocytes. Molecular and Cellular Biology, 11(2):1017-1022.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
Endothelin receptor antagonists
Definition
Endothelin receptor antagonists, by blocking the vasoconstrictor and cardiotonic effects of ET-1, produce vasodilation and cardiac inhibition. Endothelin receptor antagonists have been shown to decrease mortality and improve themodynamics in experimental models of heart failure 1.
Related Peptides
Novel cyclic pentapeptides, WS7338A, B, C and D [cyclo-(AAl -AA2-D-Trp-D-Glu-Ala)] were isolated as ET-receptor antagonists from the culture broth of Sfreptomyces sp. No. 7338 2.
Discovery
Based on conformational analysis, the minimum structural requirements for binding affinity was defined by Neya et al., and a series of acylated tripeptides with ET-A receptor binding affinity were synthesized. Through extensive chemical modification of the lead tripeptide, a potent and selective ETA receptor antagonist FR139317 was discovered. Further modification of this series of tripeptide ET antagonists has led to the discovery of a highly potent and selective ET-B receptor antagonist FR164343 2.
Structural Characteristics
Cyclic pentapeptide endothelin receptor antagonists:
WS7338A: 1 cyclo-(D-Val-Leu-D-Trp-D-Glu-Ala)
WS7338B: 2 cyclo-(D-allolle-Leu-D-Trp-D-Glu-Ma)
WS7338C: 3 cyclo-(D-Val-Val-D-Trp-D-Glu-Ala)
WS7338D: 4 cyclo-(D-Leu-Val-D-Trp-D-Glu-Ala)
Through extensive modification of the cyclic pentapeptide 2 on the basis of its conformation analysis a series of tripeptide ET receptor antagonists with ETA and ETB subtype-selectivity were discovered. Further in vivo characterization demonstrated that FR139317 is a highly potent and selective ET-A receptor antagonist, whereas FR164343 is a highly potent and selective ET-B receptor antagonist. It may be concluded that FR139317 and FR164343 are useful pharma- cological agents for investigating the pathophysiological roles of the ET system 2.
Mode of Action
ET-receptor antagonists are designed such that they have very high binding affinities to endothelin receptors (ET-A and ET-B). Therefore these antagonists mediate their action by blocking the ET receptor binding sites 2.
Functions
ET-receptor antagonists have recently been proposed as an alternative to traditional therapies for pulmonary arterial hypertension 3. ET-receptor antagonists might be useful to treat myocardial ischemia. It is possible that during chronic therapy, inhibition of the proliferative effects of ET may be beneficial for structural changes. Hence, long-term studies with ET-receptor antagonists in coronary artery disease are necessary to determine their clinical potential 4. Significant hemodynamic and neurohumoral benefits were observed in patients with severe heart failure receiving the selective endothelin antagonist 5.
References
1. Book: Cardiovascular Physiology Concepts by Klabunde RE.
2. Neya M (1997). Discovery of endothelin antagonists. Pure & Appl Chem., 69(3):441-446.
3. Liu C, Chen J, Gao Y, Deng B, Liu K (2008). Endothelin receptor antagonists for pulmonary arterial hypertension. Database of Systematic Reviews, 4:1858-1865.
4. Wenzel RR, Fleisch M, Shaw S, Noll G, Kaufmann U, Schmitt R, Jones CR, Clozel M, Meier B, Lüscher TF (1998). Hemodynamic and coronary effects of the endothelin antagonist bosentan in patients with coronary artery disease. Circulation, 98(21):2235-2240.
5. Bergler-Klein J, Pacher R, Berger R, Bojic, A, Stanek B (2004). Neurohumoral and hemodynamic effects of the selective endothelin anEndothelin Antagoniststagonist darusentan in advanced chronic heart failure. J Heart Lung Transplant., 23(1):20-27.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
Eglin c and Fragments
Definition
Eglin c is an 8.1 kDa protein proteinase inhibitor first isolated from the leech Hirudo medicinalis and now produced by genetic engineering as an N-acetyl derivative 1.
Related Peptides
Eglin c belongs to the potato inhibitor I family of serineproteinase inhibitors 1.
Discovery
Eglins are small protein inhibitors isolated from the leech Hirudo medicinalis by Seemueller et al.,in 1977 2.
Structural Characteristics
This inhibitor is composed of a single polypeptide chain of 70 amino acid residues. It is extremely stable despite the lack of disulphide bridges. This enzyme is a 25 kDa serine proteinase synthesized and stored in the pancreas as a proenzyme which is a single polypeptide chain of 241 amino acid residues 1. Eglin consists of a four-stranded beta-sheet with an alpha-helical segment and the protease-binding loop fixed on opposite sides. This loop, which contains the reactive site Leu45I--Asp46I, is mainly held in its conformation by unique electrostatic/hydrogen bond interactions of Thr44I and Asp46I with the side chains of Arg53I and Arg51I which protrude from the hydrophobic core of the molecule. The conformation around the reactive site is similar to that found in other proteinase inhibitors. The nine residues of the binding loop Gly40I--Arg48I are involved in direct contacts with subtilisin. In this interaction, eglin segment Pro42I--Thr44I forms a three-stranded anti-parallel beta-sheet with subtilisin segments Gly100--Gly102 and Ser125--Gly127. The reactive site peptide bond of eglin is intact, and Ser221 OG of the enzyme is 2.81 A apart from the carbonyl carbon 2.
Eglin C fragments:
In a study, various peptide fragments related to eglin c, which consists of 70 amino acid residues, were synthesized by a conventional solution method and their inhibitory effects on leukocyte elastase, cathepsin G and alpha-chymotrypsin were examined. Among them, H-Arg-Glu-Tyr-Phe-OMe (eglin c 22-25) and H-Ser-Pro-Val-Thr-Leu-Asp-Leu-Arg-Tyr-OMe (Eglin c 41-49) inhibited cathepsin G and alpha-chymotrypsin but not leukocyte elastase, while H-Thr-Asn-Val-Val-OMe (Eglin c 60-63) inhibited leukocyte elastase but not cathepsin G or alpha-chymotrypsin, although eglin c potently inhibited leukocyte elastase, cathepsin G and alpha-chymotrypsin. These results indicated that the interaction sites of eglin c with leukocyte elastase, cathepsin G and alpha-chymotrypsin might be different 3. In another study, a protected C-terminal triacontapeptide of eglin c, eglin c (31–70), eglin c (22–30) and eglin c (8–70) and finally eglin c were synthesized by a conventional solution method in order to study the relationship between their structure and the inhibitory activity against human leukocyte elastase, cathepsin G and a-chymotrypsin. Although the inhibitory activity of eglin c (31–70) and eglin c (22–70) against the aforementioned enzymes did not increase dramatically, eglin c (8–70) exhibited inhibitory activity against the above enzymes with similar or rather lower Ki-values than that of N a-acetyleglin c.
Mode of Action
The interaction of Eglin with subtilisin looks quite similar to the interaction observed in the proteinase complexes of the other 'small' seine proteinase inhibitor proteins, obeying the 'standard mechanism' proposed by Laskowski and Kato. In Eglin, the binding loop is in a conformation which allows it to bind tightly to the cognate enzyme, under formation of a three-stranded (a new feature, not yet observed in other complexes) intermolecular ß-sheet. This complex is in a conformation similar to that expected for a pre-transition state complex. The relatively rigid and densely packed structure of the complex and the high association rates observed suggest that the loop structure in the free inhibitor will possess a similar conformation 2.
Functions
It potently inhibits chymotrypsin, subtilisin, neutrophil elastase and cathepsin G, forms loose complexes with bovine pancreatic trypsin and pig pancreatic elastase, and does not inhibit plasmin, thrombin and kallikrein 1. Eglin-c treatment prevents MCT-induced ventilatory dysfunction and suggest that endogenous elastase may play an important role in MCT-induced inflammation-mediated ventilatory abnormality 5.
References
1. Faller B, Dirrig S, Rabaud M, Bieth JG (1990). Kinetics of the inhibition of human pancreatic elastase by recombinant eglin c. Influence of elastin. Biochem. J., 270(3):639-644.
2. Bode W, Papamokos E, Musil D, Seemueller U, Fritz H(1986).. Refined 1.2 A crystal structure of the complex formed between subtilisin Carlsberg and the inhibitor eglin c. Molecular structure of eglin and its detailed interaction with subtilisin. EMBO J., 5(4):813-818.
3. Tsuboi S, Nakabayashi K, Matsumoto Y, Teno N, Tsuda Y, Okada Y, Nagamatsu Y, Yamamoto J (1990). Amino acids and peptides. XXVIII. Synthesis of peptide fragments related to eglin c and studies on the relationship between their structure and effects on human leukocyte elastase, cathepsin G and alpha-chymotrypsin. Chem Pharm Bull., 38(9):2369-2376.
4. Okada Y, Tsuboi S (1991). Amino acids and peptides. Part 32. Total synthesis of eglin c. Part 2. Synthesis of a heptacontapeptide corresponding to the entire amino acid sequence of eglin c and of related peptides, and studies on the relationship between the structure and inhibitory activity against human leukocyte elastase, cathepsin G and a-chymotrypsin. J. Chem. Soc., 1991:3321-3328.
5. Lai YL, Zhou KR (1997). Eglin-c prevents monocrotaline-induced ventilatory dysfunction. Appl Physiol., 82:324-328.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
Eglin c and Fragments
Definition
Eglin c is an 8.1 kDa protein proteinase inhibitor first isolated from the leech Hirudo medicinalis and now produced by genetic engineering as an N-acetyl derivative 1.
Related Peptides
Eglin c belongs to the potato inhibitor I family of serineproteinase inhibitors 1.
Discovery
Eglins are small protein inhibitors isolated from the leech Hirudo medicinalis by Seemueller et al.,in 1977 2.
Structural Characteristics
This inhibitor is composed of a single polypeptide chain of 70 amino acid residues. It is extremely stable despite the lack of disulphide bridges. This enzyme is a 25 kDa serine proteinase synthesized and stored in the pancreas as a proenzyme which is a single polypeptide chain of 241 amino acid residues 1. Eglin consists of a four-stranded beta-sheet with an alpha-helical segment and the protease-binding loop fixed on opposite sides. This loop, which contains the reactive site Leu45I--Asp46I, is mainly held in its conformation by unique electrostatic/hydrogen bond interactions of Thr44I and Asp46I with the side chains of Arg53I and Arg51I which protrude from the hydrophobic core of the molecule. The conformation around the reactive site is similar to that found in other proteinase inhibitors. The nine residues of the binding loop Gly40I--Arg48I are involved in direct contacts with subtilisin. In this interaction, eglin segment Pro42I--Thr44I forms a three-stranded anti-parallel beta-sheet with subtilisin segments Gly100--Gly102 and Ser125--Gly127. The reactive site peptide bond of eglin is intact, and Ser221 OG of the enzyme is 2.81 A apart from the carbonyl carbon 2.
Eglin C fragments:
In a study, various peptide fragments related to eglin c, which consists of 70 amino acid residues, were synthesized by a conventional solution method and their inhibitory effects on leukocyte elastase, cathepsin G and alpha-chymotrypsin were examined. Among them, H-Arg-Glu-Tyr-Phe-OMe (eglin c 22-25) and H-Ser-Pro-Val-Thr-Leu-Asp-Leu-Arg-Tyr-OMe (Eglin c 41-49) inhibited cathepsin G and alpha-chymotrypsin but not leukocyte elastase, while H-Thr-Asn-Val-Val-OMe (Eglin c 60-63) inhibited leukocyte elastase but not cathepsin G or alpha-chymotrypsin, although eglin c potently inhibited leukocyte elastase, cathepsin G and alpha-chymotrypsin. These results indicated that the interaction sites of eglin c with leukocyte elastase, cathepsin G and alpha-chymotrypsin might be different 3. In another study, a protected C-terminal triacontapeptide of eglin c, eglin c (31–70), eglin c (22–30) and eglin c (8–70) and finally eglin c were synthesized by a conventional solution method in order to study the relationship between their structure and the inhibitory activity against human leukocyte elastase, cathepsin G and a-chymotrypsin. Although the inhibitory activity of eglin c (31–70) and eglin c (22–70) against the aforementioned enzymes did not increase dramatically, eglin c (8–70) exhibited inhibitory activity against the above enzymes with similar or rather lower Ki-values than that of N a-acetyleglin c.
Mode of Action
The interaction of Eglin with subtilisin looks quite similar to the interaction observed in the proteinase complexes of the other 'small' seine proteinase inhibitor proteins, obeying the 'standard mechanism' proposed by Laskowski and Kato. In Eglin, the binding loop is in a conformation which allows it to bind tightly to the cognate enzyme, under formation of a three-stranded (a new feature, not yet observed in other complexes) intermolecular ß-sheet. This complex is in a conformation similar to that expected for a pre-transition state complex. The relatively rigid and densely packed structure of the complex and the high association rates observed suggest that the loop structure in the free inhibitor will possess a similar conformation 2.
Functions
It potently inhibits chymotrypsin, subtilisin, neutrophil elastase and cathepsin G, forms loose complexes with bovine pancreatic trypsin and pig pancreatic elastase, and does not inhibit plasmin, thrombin and kallikrein 1. Eglin-c treatment prevents MCT-induced ventilatory dysfunction and suggest that endogenous elastase may play an important role in MCT-induced inflammation-mediated ventilatory abnormality 5.
References
1. Faller B, Dirrig S, Rabaud M, Bieth JG (1990). Kinetics of the inhibition of human pancreatic elastase by recombinant eglin c. Influence of elastin. Biochem. J., 270(3):639-644.
2. Bode W, Papamokos E, Musil D, Seemueller U, Fritz H(1986).. Refined 1.2 A crystal structure of the complex formed between subtilisin Carlsberg and the inhibitor eglin c. Molecular structure of eglin and its detailed interaction with subtilisin. EMBO J., 5(4):813-818.
3. Tsuboi S, Nakabayashi K, Matsumoto Y, Teno N, Tsuda Y, Okada Y, Nagamatsu Y, Yamamoto J (1990). Amino acids and peptides. XXVIII. Synthesis of peptide fragments related to eglin c and studies on the relationship between their structure and effects on human leukocyte elastase, cathepsin G and alpha-chymotrypsin. Chem Pharm Bull., 38(9):2369-2376.
4. Okada Y, Tsuboi S (1991). Amino acids and peptides. Part 32. Total synthesis of eglin c. Part 2. Synthesis of a heptacontapeptide corresponding to the entire amino acid sequence of eglin c and of related peptides, and studies on the relationship between the structure and inhibitory activity against human leukocyte elastase, cathepsin G and a-chymotrypsin. J. Chem. Soc., 1991:3321-3328.
5. Lai YL, Zhou KR (1997). Eglin-c prevents monocrotaline-induced ventilatory dysfunction. J Appl Physiol., 82:324-328.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
C-Reactive Protein Sequences
Definition
C-reactive protein (CRP) is an acute phase protein. It is phylogenetically ancient and - with serum amyloid P - belongs to proteins named as "pentraxin".
Discovery
CRP was discovered in Oswald Avery's laboratory during the course of studies of patients with Streptococcus pneumoniae infection. Sera obtained from these patients during the early, acute phase of the illness were found to contain a protein that could precipitate the “C” polysaccharide derived from the pneumococcal cell wall1.
Structural Characteristics
CRP belongs to the pentraxin family of calcium-dependent ligand-binding plasma proteins, the other member of which in humans is serum amyloid P component (SAP). The human CRP molecule (Mr 115,135) is composed of five identical nonglycosylated polypeptide subunits (Mr 23,027), each containing 206 amino acid residues. The protomers are noncovalently associated in an annular configuration with cyclic pentameric symmetry. Each protomer has the characteristic "lectin fold," composed of a two-layered ß sheet with flattened jellyroll topology. The ligand-binding site, composed of loops with two calcium ions bound 4 Å apart by protein side-chains, is located on the concave face. The other face carries a single a helix2.
Mode of Action
Human CRP binds with highest affinity to phosphocholine residues, but it also binds to a variety of other autologous and extrinsic ligands, and it aggregates or precipitates the cellular, particulate, or molecular structures bearing these ligands. Autologous ligands include native and modified plasma lipoproteins, damaged cell membranes, a number of different phospholipids and related compounds, small nuclear ribonucleoprotein particles, and apoptotic cells. Extrinsic ligands include many glycan, phospholipid, and other constituents of microorganisms, such as capsular and somatic components of bacteria, fungi, and parasites, as well as plant products. When aggregated or bound to macromolecular ligands, human CRP is recognized by C1q and potently activates the classical complement pathway, engaging C3, the main adhesion molecule of the complement system, and the terminal membrane attack complex, C5–C9. Bound CRP may also provide secondary binding sites for factor H and thereby regulate alternative-pathway amplification and C5 convertases3.
Functions
CRP, the Metabolic Syndrome, and Risk of Incident Cardiovascular Events: The metabolic syndrome describes a high-risk population having 3 or more of the following clinical characteristics: upper-body obesity, hypertriglyceridemia, low HDL, hypertension, and abnormal glucose. All of these attributes, however, are associated with increased levels of CRP. In a study, the interrelationships between CRP, the metabolic syndrome, and incident cardiovascular events was evaluated among 14,719 apparently healthy women who were followed up for an 8-year period for myocardial infarction, stroke, coronary revascularization, or cardiovascular death; 24% of the cohort had the metabolic syndrome at study entry. It was found that, at baseline, median CRP levels for those with 0, 1, 2, 3, 4, or 5 characteristics of the metabolic syndrome were 0.68, 1.09, 1.93, 3.01, 3.88, and 5.75 mg/L, respectively (Ptrend <0.0001).>
CRP and the pathogenesis of atherosclerosis: The CRP binds to lipids, especially lecithin (phosphatidyl choline), and to plasma lipoproteins, and the first suggestion of a possible relationship to atherosclerosis came when it was demonstrated that aggregated, but not native, non-aggregated, CRP selectively bound just LDL and some VLDL from whole serum. However, native CRP does bind to partially degraded, so-called modified LDL, as it is found in atheromatous plaques, and to oxidized LDL. Furthermore CRP is present in most such plaques examined ex vivo. This CRP could contribute to complement activation and thus inflammation in the plaques, and there is experimental evidence supporting a possible role of complement in atherogenesis. CRP has also been reported to stimulate tissue factor production by peripheral blood monocytes and could thereby have important pro-coagulant effects5.
Targeting CRP for the treatment of cardiovascular disease: A study, reported the design, synthesis and efficacy of 1,6-bis(phosphocholine)-hexane as a specific small-molecule inhibitor of CRP. Five molecules of palindromic compound are bound by two pentameric CRP molecules, crosslinking and occluding the ligand-binding B-face of CRP and blocking its functions. Administration of 1,6-bis(phosphocholine)-hexane to rats undergoing acute myocardial infarction abrogated the increase in infarct size and cardiac dysfunction produced by injection of human CRP. Therapeutic inhibition of CRP is thus a promising new approach to cardioprotection in acute myocardial infarction. Potential wider applications include other inflammatory, infective and tissue-damaging conditions characterized by increased CRP production, in which binding of CRP to exposed ligands in damaged cells may lead to complement-mediated exacerbation of tissue injury6.
References
1. Tillett WS, Francis Jr T (1930). Serological reactions in pneumonia with a nonprotein somatic fraction of pneumococcus. J Exp Med., 52:561–585.
2. Thompson D, Pepys MB, Wood SP (1999). The physiological structure of human C-reactive protein and its complex with phosphocholine. Structure, 7:169-177.
3. Pepys MB, Hirschfield GM (2003). C-reactive protein: a critical update. J. Clin Invest., 111(12):1805-1812.
4. Ridker PM, Buring JE, Cook NR, Rifai N (2003). C-Reactive Protein, the Metabolic Syndrome, and Risk of Incident Cardiovascular Events (An 8-Year Follow-Up of 14 719 Initially Healthy American Women). Circulation, 107(3):391-397.
5. Pepys MB, Hirschfield GM (2003). C-reactive protein and cardiovascular disease: new insights from an old molecule. Q. J. Med., 96:793-807.
6. Pepys MB, Hirschfield GM, Tennent GA, Gallimore JR, Kahan MC, Bellotti V, Hawkins PN, Myers RM, Smith MD, Polara A, Cobb AJ, Ley SV, Aquilina JA, Robinson CV, Sharif I, Gray GA, Sabin CA, Jenvey MC, Kolstoe SE, Thompson D, Wood SP (2006). Targeting C-reactive protein for the treatment of cardiovascular disease. Nature, 440(7088):1217-1221.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
C-Peptides
Angiogenin (renamed Angiogenin-1; abbr. ANG or Ang-1) is a basic heparin binding protein. Angiogenin is a potent inducer of angiogenesis.
Discovery
The first human tumor derived protein with in vivo angiogenic activity to be obtained in pure form has been isolated from serum-free supernatants of an established human adenocarcinoma cell line (HT-29) and named angiogenin, based solely on its angiogenic activity on the chicken chorioallantoic membrane. It was purified by cation-exchange and reversed-phase high-performance liquid chromatography; the yield was approximately 0.5 microgram/L of medium 1. It actually is a constituent of human plasma2, 3 and normally circulates at a concentration of 250 to 360 ng/ml.
Structural Characteristics
Bovine ANG is a single-chain protein of 125 amino acids; it contains six cysteines and has a calculated molecular weight of 14 kDa. In contrast to the human protein its amino terminus is unblocked. Bovine angiogenin is 64% identical with human angiogenin; like the human protein, it is homologous to the pancreatic ribonucleases, with conservation of active site residues. Two regions, 6-22 and 65-75, are highly conserved between the angiogenins but are significantly different from those of the ribonucleases, suggesting a possible role in the molecules' biological activity 4.
Mode of Action
ANG is a member of the ribonuclease (RNase) superfamily: enzymes of innate substrate specificity, but divergent functional capacities, where angiogenesis is commonly attributed to ANG. Its distinct structure gives angiogenin an endothelial binding motif, which it combines with its endonuclease enzyme activity to produce a potent stimulus for blood vessel formation. Phyisiologically, ANG is induced during inflammation, exhibiting wound healing properties as well as microbicidal activity and conferring host immunity. Interestingly, this protein commonly circulates at markedly high levels in human serum, without a proliferative impact 5.
Functions
ANG activates Erk1/2 in human umbilical vein endothelial cells: ANG is a potent angiogenic factor that induces transient phosphorylation of extracellular signal-related kinase1/2 (Erk1/2) in cultured human umbilical vein endothelial cells. Furthermore, ANG does not affect the phosphorylation status of stress-associated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and p38 mitogen-activated protein (MAP) kinases. PD98059--a specific inhibitor of MAP or Erk kinase 1 (MEK 1), the upstream kinase that phosphorylates Erk1/2--abolishes angiogenin-induced Erk phosphorylation and cell proliferation without affecting nuclear translocation of angiogenin. In contrast, neomycin, a known inhibitor of nuclear translocation and cell proliferation, does not interfere with ANG-induced Erk1/2 phosphorylation. These results indicate that both intracellular signaling pathways and direct nuclear functions of ANG are required for angiogenin-induced cell proliferation and angiogenesis 6.
Increased ANG expression in pancreatic cancer is related to cancer aggressiveness: In a study the expression of ANG in pancreatic cancer and the relevance of ANG expression to the progression of pancreatic cancer were investigated. It was found that in comparison to normal pancreas, increased ANG mRNA expression was observed in 80.0% of the cases of pancreatic cancer by in situ hybridization and Western blot analysis. Furthermore, the mean serum ANG concentration of pancreatic cancer patients (566.6 +/- 191.9 ng/ml) was significantly higher (P <>
Interaction of human ANG with copper modulates ANG binding to endothelial cells: ANG is a potent inducer of blood-vessel formation with ribonucleolytic activity. ANG binds to high affinity endothelial cell receptors and with lower affinity to extracellular matrix components. A study reported the effect of copper and zinc on these interactions. There is evidence that there was a 4.3-fold increase in ANG binding to calf pulmonary artery endothelial cells in the presence of Cu2+ in vitro. A 3.8-fold increase was observed with Zn2+, whereas Ni2+, Co2+, or Li+ had no effect. Specific angiogenin binding to the lower affinity matrix sites was increased by 2.7- and 1.9-fold in the presence of Cu2+ and Zn2+ respectively. ANG bound 2.4 mol of copper per mole of protein. Thus, these results suggest that copper, a modulator of angiogenesis in vivo, may be involved in the regulation of the biological activity of angiogenin7.
References
1. Fett JW, Strydom DJ, Lobb RR, Alderman EM, Bethune JL, Riordan JF, Vallee BL (1985). Isolation and characterization of angiogenin, an angiogenic protein from human carcinoma cells. Biochemistry., 24(20):5480-5486.
2. Shimoyama S, Gansauge F, Gansauge S, Negri G, Oohara T, Beger HG (1996). Increased angiogenin expression in pancreatic cancer is related to cancer aggressiveness. Cancer. Res., 56(12):2703-2706.
3. Bläser J, Triebel S, Kopp C, Tschesche H (1993). A highly sensitive immunoenzymometric assay for the determination of angiogenin. Eur J. Clin. Chem Clin Biochem., 31(8):513-516.
4. Bond MD, Strydom DJ (1989). Amino acid sequence of bovine angiogenin. Biochemistry, 28(14):6110-6113.
5. Tello-Montoliu A, Patel JV, Lip GYH (2006). Angiogenin: a review of the pathophysiology and potential clinical applications. J. Thromb. Haemost., 4: 864-874.
6. Liu S, Yu D, Xu ZP, Riordan JF, Hu GF (2001). Angiogenin activates Erk1/2 in human umbilical vein endothelial cells. Biochem. Biophys. Res. Commun., 287(1):305-310.
7. Soncin F, Guitton JD, Cartwright T, Badet J (1997). Interaction of human angiogenin with copper modulates angiogenin binding to endothelial cells. Biochem Biophys Res Commun., 236(3):604-610.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
Amyloid Peptides
Definition Amyloids are filamentous protein deposits ranging in size from nanometres to microns and composed of aggregated peptide beta-sheets formed from parallel or anti-parallel alignments of peptide beta-strands.
Structural Characteristics
Using Solid-State NMR (SSNMR), in conjunction with computational energy minimization procedures, Tycko and coworkers have put forward a structure of the amyloid fibrils formed from the 40-residue form of the amyloid ß peptide (Aß1-40) at pH 7.4 and 24oC under quiescent conditions1, 2, 3. In this structure, each Aß1-40 molecule contributes a pair of ß-strands, spanning approximately residues 12–24 and 30–40, to the core region of the fibrils. These strands, connected by the loop 25–29, are not part of the same ß-sheet, however, but participate in the formation of two distinct ß-sheets within the same protofilament. The different Aß molecules2, 3 are stacked on to each other, in a parallel arrangement and in register, at least from residue 9 to 39. By invoking additional experimental constraints, such as the diameter of the protofilaments observed using Transmission electron microscopy (TEM), and the mass per unit length, measured by means of scanning transmission electron microscopy (STEM) 1, 2 it has been suggested that a single protofilament is composed of four ß-sheets separated by distances of ~10 Å.
Mode of Action
Alzheimer's disease (AD) is a result of filamentous deposits of amyloid, which define the disease at the molecular level, occur within perikarya, axons, dendrites, and terminals of neurons as neurofibrillary tangles (NFT), in the extracellular neuropil as amyloid plaques (APC), and around blood vessels as amyloid congophilic angiopathy (ACA). The amyloid deposits apparently occur in the terminal zones of neurons that develop NFT. It has been suggested that the major constituent of both APC and ACA has been shown to be a 4.5-kDa amyloid protein originally termed "beta-protein" or "amyloid A4" which we now denote as "beta A4." Amyloid beta A4 protein is proteolytically derived from a transmembrane protein termed amyloid precursor protein (APP) which is encoded by a widely expressed gene on chromosome 214.
Functions
Calcium dysregulation and membrane disruption as a ubiquitous neurotoxic mechanism of soluble amyloid oligomers: A study was conducted to investigate the possible involvement of Ca2+ signaling disruptions in amyloid-induced cytotoxicity, homogeneous preparations of disease-related amyloids (beta, prion, islet amyloid polypeptide, polyglutamine, and lysozyme) in various aggregation states were made and tested their actions on fluo-3-loaded SH-SY5Y cells. Application of oligomeric forms of all amyloids tested (0.6-6 µg /ml) rapidly (approximately 5 s) elevated intracellular Ca2+, whereas equivalent amounts of monomers and fibrils did not. Ca2+signals evoked by Abeta42 oligomers persisted after depletion of intracellular Ca2+ stores, and small signals remained in Ca2+-free medium, indicating contributions from both extracellular and intracellular Ca2+ sources. The increased membrane permeability to Ca2+ cannot be attributed to activation of endogenous Ca2+ channels, because responses were unaffected by the potent Ca2+-channel blocker cobalt. Instead, observations that Abeta42 and other oligomers caused rapid cellular leakage of anionic fluorescent dyes point to a generalized increase in membrane permeability. The resulting unregulated flux of ions and molecules may provide a common mechanism for oligomer-mediated toxicity in many amyloidogenic diseases, with dysregulation of Ca2+ ions playing a crucial role because of their strong trans-membrane concentration gradient and involvement in cell dysfunction and death 5.
Islet amyloid in type 2 diabetes, and the toxic oligomer hypothesis: Type 2 diabetes (T2DM) is characterized by insulin resistance, defective insulin secretion, loss of beta-cell mass with increased beta-cell apoptosis and islet amyloid. The islet amyloid is derived from islet amyloid polypeptide (IAPP, amylin), a protein coexpressed and cosecreted with insulin by pancreatic beta-cells. In common with other amyloidogenic proteins, IAPP has the propensity to form membrane permeant toxic oligomers. Accumulating evidence suggests that these toxic oligomers, rather than the extracellular amyloid form of these proteins, are responsible for loss of neurons in neurodegenerative diseases. It has been suggested that formation of intracellular IAPP oligomers may contribute to beta-cell loss in T2DM6.
References
1. Petkova AT, Ishii Y, Balbach JJ, Antzutkin ON, Leapman RD, Delaglio F, Tycko R (2002). A structural model for Alzheimer's ß-amyloid fibrils based on experimental constraints from solid state NMR. PN AS., 99(26):16742–16747.
2. Antzutkin ON, Balbach JJ, Leapman RD, Rizzo NW, Reed J, Tycko R (2000). Multiple quantum solid-state NMR indicates a parallel, not antiparallel, organization of ß-sheets in Alzheimer's ß-amyloid fibrils. PNAS., 97:13045-13050.
3. Balbach JJ, Petkova AT, Oyler NA, Antzutkin ON, Gordon DJ, Meredith SC, Tycko R (2002). Supramolecular Structure in Full-Length Alzheimer's ß-Amyloid Fibrils: Evidence for a Parallel ß-Sheet Organization from Solid-State Nuclear Magnetic Resonance. Biophys. J., 83:1205-1216.
4. Beyreuther K, Bush AI, Dyrks T, Hilbich C, König G, Mönning U, Multhaup G, Prior R, Rumble B, Schubert W (1991). Mechanisms of amyloid deposition in Alzheimer's disease. Ann N Y Acad Sci., 640:129-139.
5. Demuro A, Mina E, Kayed R, Milton SC, Parker I, Glabe CG (2005). Calcium dysregulation and membrane disruption as a ubiquitous neurotoxic mechanism of soluble amyloid oligomers. J. Biol. Chem., 280(17):17294-17300.
6. Haataja L, Gurlo T, Huang CJ, Butler PC (2008). Islet amyloid in type 2 diabetes, and the toxic oligomer hypothesis. Endocr. Rev., 29(3):303-316.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
DefinitionThe enzyme renin, which is found in extracts of kidney cortex, acts upon a protein substrate contained in the alpha-2 globulin fraction of the plasma to produce the decapeptide hypertensin I. This peptide is further degraded by a plasma enzyme to the powerfully vasoconstrictor octapeptide hypertension II which appears to be the effector substance of the renin-hypertensin pressor system 1.
Related PeptidesRenin substrate protein is a member of the serpin family.DiscoveryThe history of the discovery of the renin-angiotensin system began in 1898 with the studies made by Tigerstedt and Bergman, who reported the pressor effect of renal extracts; they named the renal substance renin based on its origin. In 1934, Harry Goldblatt induced experimental hypertension in dogs by clamping a renal artery. About 1936, simultaneously in the Medical School of the University of Buenos Aires, Argentina, and in the Eli-Lilly Laboratories in Indianapolis, 2 independent groups of researchers, using the Goldblatt technique to produce experimental hypertension, demonstrated renal secretion of a pressor agent similar to renin. In the following years, both teams described the presence of a new compound in the renal vein blood of ischemic kidneys. This The final conclusion was that renin acted enzymatically on a plasma protein called the renin substrate to produce the new substance. In Buenos Aires, it was called hypertensin; in the United States, angiotonin. In 1958, Eduardo Braun Menéndez from Argentina and Irving H. Page from the United States agreed to name it angiotensin 2.Structural CharacteristicsThe present understanding of the mechanism of the renin-hypertensin pressor system may be summarized in the following equations: asp-arg-val-tyr-ileu-hls-pro-phe-his-leu-leu-val-tyr-ser – R (protein substrate) I reninasp-arg-val-tyr-ileu-Ms-pro-phe-his-leu + leu-val-tyr-ser - R(hypertensin I) I Converting enzyme (CI-) asp-arg-val-tyr-ileu-his-pro-phe + his-leu (hypertensin II) vasoconstrictorRenin breaks the leucyl-leucine bond of the substrate setting free hypertensin I it is clear that the point of attachment of the polypeptide substrate molecule to the parent protein must be at either the serine carboxyl or hydroxyl group. The renin substrate molecule is completely unaffected by a hypertensin-converting enzyme with which it is in intimate contact in the plasma. Neither is the purified polypeptide substrate affected by this enzyme. The leucine carboxyl group of hypertensin I becomes available only after this decapeptide is released from the substrate molecule. It is suggested therefore that this group must be free in order to satisfy the specific requirements of the converting enzyme and allow hydrolysis of the phenylalanyl-histidine bond of hypertensin I 1.On the basis of the minimal octapeptide sequence of the renin substrate, a series of peptides was synthesized containing (3S, 4S)-4-amino-3-hydroxy-6-methylheptanoic acid (statine) or (3S,4S)-4-amino-3-hydroxy-5-phenylpentanoic acid (AHPPA) at the P1P1' position. Some of these peptides also contained Nin-formyltryptophan at the P5, P3, or P3' position. Renin-inhibitory potency varied over a wide range (from inactive to IC50 = 3 nM). Potency was reduced by at least 10-fold when the peptide was shortened by two residues at either the amino or carboxy terminus. Studies on the plasma renins of four nonhuman species suggest that the isoleucine-histidine segment at the P2'P3' position is important to defining the human specificity of the substrate 3.A synthetic tetradecapeptide, H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-His-Ser-OH, which corresponds to the 13 amino terminal residues of human angiotensinogen plus a carboxy terminal serine to replace a suggested site of carbohydrate attachment, has been shown to be a good substrate for human kidney renin . Thus, this synthetic renin substrate should permit more specific measurement of human kidney renin activity 4.References and further reading may be available for this article. To view references and further reading you must purchase this article.Mode of ActionThe enzyme renin, which is found in extracts of kidney cortex, acts upon a protein substrate contained in the alpha-2 globulin fraction of the plasma to produce the decapeptide hypertensin I. This peptide is further degraded by a plasma enzyme (2) to the powerfully vasoconstrictor octapeptide hypertension II which appears to be the effector substance of the renin-hypertensin pressor system 1.FunctionsSynthetic renin substrates are useful as renin inhibitors and in specific measurement of human kidney renin activity 3, 4.References1.Skeggs LT Jr, Kahn JR, Lentz K, Shumway NP (1957). The preparation, purification and amino acid sequence of a polypeptide renin substrate. J Exp Med., 106:439-453.2.Basso N, Terragno NA (2001). History About the Discovery of the Renin-Angiotensin System. Hypertension. 38(6):1246-1249.3.Hui KY, Carlson WD, Bernatowicz MS, and Haber E (1987). Analysis of structure-activity relationships in renin substrate analogue inhibitory peptides. J med chem., 30(8):1287-1295.4.Poe M, Wu JK, Lin TY, Hoogsteen K, Bull HG, Slater EE (1984). Renin cleavage of a human kidney renin substrate analogous to human angiotensinogen, H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-His-Ser-OH, that is human renin specific and is resistant to cathepsin D. Anal Biochem., 140(2):459-467.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
Definition
The neurohypophysial hormone oxytocin (OT) was the first peptide hormone to have its structure determined and the first to be chemically synthesized in biologically active form. It is named after the “quick birth” which it causes due to its uterotonic activity. OT was also found to be responsible
for the milk-ejecting activity of the posterior pituitary gland 1.
Related Peptides
Vasopressin and OT are nonapeptides that are present in all placental mammals. Although similar in structure, they serve different functions. Peptides of the vasopressin family have a basic amino acid residue at position 8 in common, whereas OT and related peptides have a neutral amino acid residue at this position. The chemical nature of this amino acid residue is thought to be of critical importance in the interactions of the peptides with their respective receptors 2.
Analogs
It has been reported that the inhibitory properties of [2-0-methyltyrosine]-oxytocin (methyloxytocin) can be accentuated by additional substitution of the terminal amino group by a carbamoyl residue. While methyloxytocin acts as an inhibitor of OT on some assay systems and has an OT-like action on others, its N-carbamoyl derivative acts as an antagonist on all the systems which are generally used for the assay of oxytocin 3. Corey-Pauling-Koltun models of [Gly7] deaminooxytocin, deaminotocinamide, and their respective retro-D-analogs are essential for "occupation" and "activation" of uterine receptors4. The protracted effect of [2-O-methyltyrosine]-deamino-1-carba-oxytocin, [2-O-methyltyrosine]-oxytocin and its dimeric form studied on the mammary gland of lactating rat in vivo showed a biphasic course of biological response that led to the assumption that the substances behaved like hormonogens5. Replacement of the amide groups of Gln(4) and Asn(5) in OT by tetrazole analogues of aspartic, glutamic and alpha-aminoadipic acids containing the tetrazole moiety in the side chains leads to analogues with decreased biological activities6. 1-Butanoic acid-2-(O-methyl-L-tyrosine)-1-carbaoxytocin (carbetocin) and/or other long-acting oxytocin analogues are formulated with a pharmaceutically acceptable carrier and administered in an amount sufficient to inhibit initiation or growth of breast cancer in the patient. The carbetocin and/or other long-acting OT analogues may also be formulated with a pharmaceutically acceptable carrier and administered in an amount sufficient to treat, prevent or alleviate the symptoms of a psychiatric disorder in the patient7, 8.
Discovery
OT and vasopressin were isolated and synthesized by Vincent du Vigneaud in 1953. The structure of the OT gene was elucidated in 1984, and the sequence of the OT receptor was reported in 1992 2.
Structural Characteristics
All neurohypophysial hormones are nonapeptides with a disulfide bridge between Cys residues 1 and 6. This results in a peptide constituted of a six-amino acid cyclic part and a COOH-terminal a-amidated three-residue tail. Based on the amino acid at position 8, these peptides are classified into vasopressin and OT families: the vasopressin family contains a basic amino acid (Lys, Arg), and the OT family contains a neutral amino acid at this position. Isoleucine in position 3 is essential for stimulating OT receptors and Arg or Lys in position 8 for acting on vasopressin receptors. The difference in the polarity of these amino acid residues is believed to enable the vasopressin and OT peptides to interact with the respective receptors 1.
Mode of Action
The OT receptor is a typical member of the rhodopsin-type (class I) GPCR family. The seven transmembrane a-helices are most highly conserved among the GPCR family members. Conserved residues among the GPCRs may be involved in a common mechanism for activation and signal transduction to the G protein. OT receptors are functionally coupled to Gq/11 a class GTP binding proteins that stimulate together with Gß? the activity of phospholipase C-ß isoforms. This leads to the generation of inositol trisphosphate and 1, 2-diacylglycerol. Inositol trisphosphate triggers Ca2+ release from intracellular stores, whereas diacylglycerol stimulates protein kinase C, which phosphorylates unidentified target proteins. Finally, in response to an increase of intracellular [Ca2+], a variety of cellular events are initiated.
Functions
Stimulation of milk ejection (milk letdown): Mammary alveoli are surrounded by smooth muscle (myoepithelial) cells which are a prominant target cell for OT. OT stimulates contraction of myoepithelial cells, causing milk to be ejected into the ducts and cisterns.
Stimulation of uterine smooth muscle contraction at birth: During the later stages of gestation, there is an increase in abundance of OT receptors on uterine smooth muscle cells, which is associated with increased "irritability" of the uterus (and sometimes the mother as well). OT is released during labor when the fetus stimulates the cervix and vagina, and it enhances contraction of uterine smooth muscle to facilitate parturition or birth.
In cases where uterine contractions are not sufficient to complete delivery, physicians and veterinarians sometimes administer OT (pitocin) to further stimulate uterine contractions.
Establishment of maternal behavior: During parturition, there is an increase in concentration of OT in cerebrospinal fluid, and OT acting within the brain plays a major role in establishing maternal behavior1.
References
1.Gimpl G, Fahrenholz F (2001). The Oxytocin Receptor System:Structure, Function, and Regulation. Physiol Rev., 81(2):629-683.
2.Van Kesteren RE, Smit AB, De Lange RP, Kits KS, Van Golen FA, Van Der Schors RC, De With ND, Burke JF, Geraerts WP (1995). Structural and Functional Evolution of the Vasopressin/Oxytocin Superfamily: Vasopressin-Related Conopressin Is the Only Member Present in Lymnaea, and Is Involved in the Control of Sexual Behavior. J Neurosci., 15(9): 5989-5998.
3.Bisset GW, Clark BJ, Krejci I, Polacek I, Rudinger J (1970). Some pharmacological properties of a synthetic oxytocin analogue 11-N-carbamoyl-hemicystine-2-0-methyltyrosinel-oxytocin (carbamoylmethyloxytocin), an antagonist to the neurohypophysial hormones. Br. J. Plarinac., 40: 342-360.
4.Hechter O, Kato T, Nakagawa SH, Yang F, Flouret G (1975). Contribution of the Peptide Backbone to the Action of Oxytocin Analogs (stereoisomers/hormone action). PNAS., 72(2):563-566.
5.Barth T, Flegel M, Jost K (1976. Protracted milk-ejecting effect of some oxytocin analogues in rats. Endocrinol Exp., 10(1):65-71.
6.Manturewicz M, Grzonka Z, Borovicková L, and Slaninová J (2007). Oxytocin analogues with amide groups substituted by tetrazole groups in position 4, 5 or 9. Acta biochimica Polonica, 54(4):805.
7.Cassoni P, Sapino A, Papotti M, Bussolati G(1996). “Oxytocin and Oxytocin-Analogue F314 Inhibit cell Proliferation and Tumor Growth of Rat and Mouse mammary carcinomas,” Int. J. Cancer., 66(6):817-820.
8.Cassoni P, Sapino A, Fortunati N, Munaron L, Chini B, Bussolati G (1997). “Oxytocin Inhibits the Proliferation of MDA-MB231 Human Breast-Cancer Cells Via Cyclic Adenosine Monophosphate and Protein Kinase A,” Int. J. Cancer., 72:340-344.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
Definition
Orexins (hypocretins) are neuropeptides primarily localized in the hypothalamus and are implicated in the regulation of a variety of activities, including feeding behavior and energy balance. Orexins have also been found to be linked to idiopathic narcolepsy (excessive daytime sleepiness) 1.
Related Peptides
Two homologous peptides, orexin-A (OXA) and orexin-B (OXB), are proteolytic cleavage products derived from a common precursor called prepro-orexin1.
Discovery
The orexins were discovered during a search for endogenous ligands that activate orphan G protein-coupled receptors by Sakurai et al., in 19982.
Structural Characteristics
OXA is 33 amino acids in length, with an N-terminal pyroglutamyl residue and an amidated C terminus. The peptide also contains two intrachain disulfide bonds, and sequencing of similar extracts from bovine brain revealed exact interspecies homology. OXB is 28 amino acids in length and is 46% (13/28) identical in sequence to OXA, with an amidated C-terminal2.
Mode of Action
The original HFGAN72 receptor, subsequently called OX1R, was shown to bind OXA with high affinity and bind OXB with 100- to 1,000-fold lower affinity. However, a related receptor, OX2R, identified by searching database entries with the OX1R sequence, was demonstrated to have equally high affinities for both peptides. Thus, OX2R was concluded to be a non-selective receptor for both OXA and OXB peptides, while OX1R was concluded to be moderately selective for orexin-A. The binding of both ligands to either receptor was associated with changes in intracellular calcium concentrations. Evidence from receptor-expressing cells suggests that OX1R is coupled exclusively to the Gq subclass of G proteins, whereas OX2R may couple to Gi/o and/or Gq 1.
Functions
The widespread projections of the orexin neurons throughout the neuroaxis suggest that activation of orexin circuits probably modulates a variety of systems, including those involved in the regulation of food intake. The fact that orexins can increase the release of either excitatory or inhibitory neurotransmitters, by acting directly on axon terminals, indicates that the peptides could ultimately increase or decrease the activity of innervated brain circuits.
OXA has been reported to increase food intake. Orexins appear to be involved in the short-term regulation of feeding, rather than the long-term maintenance of body weight. OXA appears to increase food intake by delaying behavioral satiety, i.e., the normal transition from eating through grooming to resting. Metabolic effects of orexins have also been shown to be dependent on circadian phase. Orexin neurons are not only play essential roles in the control of feeding and energy balance but also regulate wakefulness. OXA inhibits the activity of glucoresponsive neurons. They control vagal outflow to the gastrointestinal tract and modulate activities such as gastric acid secretion and/or motility. Orexins probably play a role in sensory transmission.
They increase blood pressure and heart rate, affect the release of luteinizing hormone, growth hormone, and Prolactin, increase drinking and locomotor activity, and maintain wakefulness. Since orexin receptors are expressed in the adrenal medulla, orexins may also modulate epinephrine release. These findings indicate that orexins play a role in the regulation of the autonomic and neuroendocrine systems, including stimulation of sympathetic nerves. Interestingly, many of these effects are also associated with changes in food intake and gastrointestinal motility. For example, sleep has been shown to be a major determinant of interdigestive and digestive motility. Sleep is associated with diminished intestinal motility during the night and the day, suggesting that intestinal motility is regulated not only by circadian rhythm. Fasting alters sleep-wake cycles and evokes a specific motor activity, the migrating motor complex, in the gut. Thus, sleep-wake, motility, and feeding patterns appear to be coordinated, and orexins may play a significant role in coordinating these complex physiological activities1.
References
1.Kirchgessner AL (2002). Orexins in the Brain-Gut Axis. Endocr Rev., 23(1):1-15
2.Sakurai T, Amemiya A, Ishii M, Matsuzaki I, Chemelli RM, Tanaka H, Williams SC, Richardson JA, Kozlowski GP, Wilson S, Arch JR, Buckingham RE, Haynes AC, Carr SA, Annan RS, McNulty DE, Liu WS, Terrett JA, Elshourbagy NA, Bergsma DJ, Yanagisawa M (1998). Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior. Cell.,92(4):573-585.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
Definition
Obestatin is a 23–amino acid amidated peptide, was originally reported to be the ligand for the orphan receptor G-protein– coupled receptor 39 (GPR39)1.
Related Peptides
Obestatin is a novel hormone that is encoded by the Ghrelin gene and produced in the gut. Ghrelin is profoundly orexogenic and adipogenic, increasing food intake and body weight, while this ghrelin-associated peptide behaves as a physiological opponent of ghrelin in rodent animals2.
Discovery
Obestatin and its derivative, an 11 amino acid fragment, Ob (11-23) were isolated by Zhang et al., in 20053.
Structural Characteristics
Obestatin and its derivative Ob (11–23) are peptides produced in the rat stomach. Both peptides assume a regular secondary structure in the C-terminal region of the molecule. They show a carboxyl-terminal amide functionality, which is flanked by mono basic residues in the pre-proghrelin sequence in the form of a Gly-extended structure. In this region, structural elements similar to other GPCR binding neuropeptides support the identity of obestatin as a new and functionally autonomous GPCR ligand4. Three overlapping fragments spanning residues 1-13, 6-18, and 11-23 of obestatin where tested upon adult male mice for their ability to reduce feed intake and gain in body weight. The N-terminal peptide (residues 1-13) mimicked obestatin the closest. The middle fragment (residues 6-18) significantly reduced epididymal fat without much altering feed intake or body weight5.
Mode of Action
The G-protein coupled receptor, GPR39, was originally proposed as being an obestatin target receptor, but this remains controversial1.
Functions
Obestatin has been reported to reduce food intake, body weight gain, gastric emptying, and jejunal motility. Moreover, it was found to counteract ghrelin stimulatory effects on these end points and to inhibit ghrelin induced growth hormone secretion in vivo but not in vitro, suggesting that it would serve as a physiological opponent of ghrelin. However, a number of studies failed to confirm obestatin anorexigenic effects. Obestatin has been reported to inhibit thirst and to influence memory, anxiety, and sleep via central activities. At the cellular level, it stimulates proliferation of human retinal cells. Obestatin promotes ß-cell and human islet cell survival and stimulates the expression of main regulatory ß-cell genes1.
References
1.Granata R, Settanni F, Gallo D, Trovato L, Biancone L, Cantaluppi V, Nano R, Annunziata M, Campiglia P, Arnoletti E, Ghè C, Volante M, Papotti M, Muccioli G, Ghigo E (2008). Obestatin Promotes Survival of Pancreatic ß-Cells and Human Islets and Induces Expression of Genes Involved in the Regulation of ß-Cell Mass and Function. Diabetes., 57(4):967–979.
2.Qi X, Li L, Yang G, Liu J, Li K, Tang Y, Liou H, Boden G (2007). Circulating obestatin levels in normal subjects and in patients with impaired glucose regulation and type 2 diabetes mellitus. Clin Endocrinol (Oxf)., 66(4):593-597.
3.Zhang JV, Ren PG, Avsian-Kretchmer O, Luo CW, Rauch R, Klein C, Hsueh AJ (2005). Obestatin, a peptide encoded by the ghrelin gene, opposes ghrelin's effects on food intake. Science., 310(5750):996-999.
4.Scrima M, Campiglia P, Esposito C, Gomez-Monterrey I, Novellino E, D'Ursi AM (2007). Obestatin conformational features: A strategy to unveil obestatin’s biological role? Biochem Biophys Res Comm.,363(3): 500-505.
5.Nagaraj S, Peddha MS, Manjappara UV (2008). Fragments of obestatin as modulators of feed intake, circulating lipids, and stored fat. Biochem bioys res commun., 366(3):731-737.
For more detail regarding Peptide please visit here : Custom Peptide Synthesis
