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A tetrapeptide is a peptide, classified as an oligopeptide, since it only consists of four amino acids joined by peptide bonds. Many tetrapeptides are pharmacologically active, often showing affinity and specificity for a variety of receptors in protein-protein signaling. Present in nature are both linear and cyclic tetrapeptides, tetrapeptides may be cyclized by a fourth peptide bond or other covalent bonds. Examples of tetrapeptides are: * Tuftsin (L-threonyl-L-lysyl-L-prolyl-L-arginine) is a peptide related primarily to the immune system function. * Rigin (glycyl-L-glutaminyl-L-prolyl-L-arginine) is a tetrapeptide with functions similar to those of tuftsin. * Postin (Lys-Pro-Pro-Arg) is the N-terminal tetrapeptide of cystatin C and an antagonist of tuftsin. * Endomorphin-1 (H-Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (H-Tyr-Pro-Phe-Phe-NH2) are peptide amides with the highest known affinity and specificity for the μ opioid receptor. * Morphiceptin (H-Tyr-Pro-Phe-Pro-NH2) is a casomorphin peptide isolated from β-casein. * Gluten exorphines A4 (H-Gly-Tyr-Tyr-Pro-OH) and B4 (H-Tyr-Gly-Gly-Trp-OH) are peptides isolated from gluten. * Tyrosine-MIF-1 (H-Tyr-Pro-Leu-Gly-NH2) is an endogenous opioid modulator. * Tetragastrin (''N''-((phenylmethoxy)carbonyl)-L-tryptophyl-L-methionyl-L-aspartyl-L-phenylalaninamide) is the C-terminal tetrapeptide of gastrin. It is the smallest peptide fragment of gastrin which has the same physiological and pharmacological activity as gastrin. * Kentsin (H-Thr-Pro-Arg-Lys-OH) is a contraceptive peptide first isolated from female hamsters. * Achatin-I (glycyl-phenylalanyl-alanyl-aspartic acid) is a neuroexcitatory tetrapeptide from giant African snail (''Achatina fulica''). * Tentoxin (cyclo(''N''-methyl-L-alanyl-L-leucyl-''N''-methyl-''trans''-dehydrophenyl-alanyl-glycyl)) is a natural cyclic tetrapeptide produced by phytopathogenic fungi from genus ''Alternaria''. * Rapastinel (H-Thr-Pro-Pro-Thr-NH2) is a partial agonist of the NMDA receptor. *HC-toxin, cyclo(D-Pro-L-Ala-D-Ala-L-Aeo), where Aeo is 2-amino-8-oxo-9,10-epoxidecanoic acid, is a virulence factor for the fungus Cochliobolus carbonum on its host, maize. ==See also== *Dipeptide *Tripeptide *Pentapeptide *Decapeptide *cyclic peptide 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「tetrapeptide」の詳細全文を読む スポンサード リンク
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