- peptide
- A compound of two or more amino acid s 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 p. bond, –CO–NH–; i.e., a substituted amide. Cf.:eupeptide bond, isopeptide bond.- atrial natriuretic p. (ANP) (na′tre-oo-ret′ik) a 28–amino acid p. (α-ANP), derived from cardiac atria, several smaller fragments of α-ANP, and a dimer of α-ANP with 56 amino acid s (β-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. SYN: atriopeptin, cardionatrin.- bitter peptides peptides that have a bitter taste and may spoil certain foods; often contain high proportions of leucyl, valyl, and aromatic amino acyl residues.- bradykinin-potentiating p. SYN: teprotide.- calcitonin gene-related p. (CGRP) a second product transcribed from the calcitonin gene. CGRP is found in a number of tissues including nervous tissue. It is a vasodilator that may participate in the cutaneous triple response.- cyclic p. a p. that forms a ring structure; E.G., tyrocidin A, an antibiotic, is a cyclic decapeptide; valinomycin is a cyclic depsipeptide.- glucagonlike p. a gut hormone that slows gastric emptying and stimulates insulin secretion. It may become useful in the future in the treatment of noninsulin-dependent diabetes mellitus, perhaps administered by patch, inhaler, or buccal pellet formulation.- glucagonlike insulinotropic p. an insulinotropic substance originating in the gastrointestinal tract and released into the circulation following ingestion of a meal containing glucose.- heterodetic p. a p. that contains p. bonds as well as covalent linkages between certain amino acyl residues that are not p. bonds; e.g., valinomycin, oxytocin. [hetero- + G. detos, bound, fr. deo, to bind, + -ic]- heteromeric p. a p. that, on hydrolysis, yields substances other than amino acid s in addition to amino acid s; e.g., pteroylglutamic acid.- homodetic p. a p. in which all of the covalent linkages between the constituent amino acid s are p. bonds; E.G., bradykinin. [homo- + G. detos, bound, fr. deo, to bind, + -ic]- homomeric p. 1. a p. that, on hydrolysis, yields only amino acid s; e.g., glutathione; 2. a p. that consists of only one particular amino acid; e.g., alanylalanylalanine.- parathyroid hormone-related p. a hormone that can be produced by tumors, especially of the squamous cell type; massive overproduction can lead to hypercalcemia and other manifestations of hyperparathyroidism. PTHrP exerts a biologic action similar to that of parathyroid hormone (PTH), acting via the same receptor, which is expressed in many tissues but most abundantly in kidney, bone, and growth plate cartilage. It apparently has significant actions during development, but it is uncertain whether PTHrP circulates at all or has any function in normal human adults. The structure of the gene for human PTHrP is more complex than that of PTH, and varying molecular forms exist, including proteins of 141, 139, and 173 amino acid s, which share a significant homology with parathyroid hormone.- phenylthiocarbamoyl p., PTC p. the p. formed by combination of phenylisothiocyanate and an α-amino group of a p.. SEE ALSO: phenylthiohydantoin.- S p. 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 6.3.2.x] any enzyme that catalyzes the synthesis of p. bonds, with the concomitant hydrolysis of a nucleoside triphosphate.
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pep·tide 'pep-.tīd n any of various amides that are derived from two or more amino acids by combination of the amino group of one acid with the carboxyl group of another and are usu. obtained by partial hydrolysis of proteinspep·tid·ic pep-'tid-ik adj* * *
n.a molecule consisting of two or more amino acid linked by bonds between the amino group (-NH) and the carboxyl group (-CO). This bond is known as a peptide bond. See also polypeptide.* * *
pep·tide (pepґtīd) any member of a class of compounds of low molecular weight that yield two or more amino acids on hydrolysis. They are the constituent parts of proteins and are formed by loss of water from the NH2 and COOH groups of adjacent amino acids. Peptides are known as di-, tri-, tetra- (etc.) peptides depending on the number of amino acids in the molecule. See also polypeptide.
Medical dictionary. 2011.
