peptide (pep´tId)

A compound of two or more amino acids in which a carboxyl group of one is united with an amino group of another, with the elimination of a molecule of water, thus forming a peptide bond, -CO-NH-; i.e., a substituted amide. Cf. eupeptide bond, isopeptide bond.
adrenocorticotropic p. a p. with ACTH activity, isolated from pituitary extracts.
anionic neutrophil activating p. (ANAP) interleukin-8
atrial natriuretic p. (ANP) (na´tre-u-ret´ik) a 28 amino acid p. (a-ANP), derived from cardiac atria, several smaller fragments of a-ANP, and a dimer of a-ANP with 56 amino acids (beta-ANP) that are present in plasma in heart failure. ANP actions include increasing capillary filtration, and renal salt and water excretion, and decreasing arterial pressure and the secretion of renin, angiotensin, aldosterone, and antidiuretic hormone.atriopeptin, cardionatrin;
bitter p.'s p.'s that have a bitter taste and may spoil certain foods; often contain high proportions of leucyl, valyl, and aromatic amino acid residues.
bradykinin-potentiating p. teprotide
calcitonin gene related p. (CGRP) (kal´sI-to´nin) a second product transcribed from the calcitonin gene. Calcitonin gene related p. is found in a number of tissues including nervous tissue. It is a vasodilator that may participate in the cutaneous triple response.
corticotropin-like intermediate-lobe p. (CLIP) product of propiomelanocortin with unknown function.
cyclic p. a p. that forms a ring structure; e.g., tyrocidin A, an antibiotic, is a cyclic decapeptide; valinomycin is a cyclic depsipeptide.
gastric inhibitory p. (GIP) gastric inhibitory polypeptide
heterodetic p. a p. that contains p. bonds as well as covalent linkages between certain amino acid residues that are not p. bonds; e.g., valinomycin, oxytocin. [hetero- + G. detos, bound, fr. deo, to bind, + -ic]
heteromeric p. a p. which, on hydrolysis, yields substances other than amino acids in addition to amino acids; e.g., pteroylglutamic acid.
homodetic p. a p. in which all of the covalent linkages between the constituent amino acids are p. bonds; e.g., bradykinin. [homo- + G. detos, bound, fr. deo, to bind, + -ic]
homomeric p. 1. a p. which, on hydrolysis, yields only amino acids; e.g., glutathione; 2. a p. which consists of only one particular amino acid; e.g., alanylalanylalanine.
p. hydrolase [EC subclass 3.4] peptidase
phenylthiocarbamoyl p. , PTC p. the p. formed by combination of phenylisothiocyanate and an a-amino group of a peptide. See also phenylthiohydantoin.
S p. See S protein.
sigma p. a p. with one end bonded to a point within the chain, usually by means of the disulfide group of a cystine residue, so that only one end of the p. is free; so called since the p. chain has then the rough shape of the Greek letter sigma; e.g., oxytocin.
p. synthetase [EC sub-subclass 6.3.2] any enzyme that catalyzes the synthesis of peptide bonds, with the hydrolysis of a nucleoside triphosphate.
vasoactive intestinal p. vasoactive intestinal polypeptide


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