Polypeptide

A compound consisting of 2 or more amino acids. Amino acids make up polypeptides which, in turn, make up proteins.

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A peptide formed by the union of an indefinite (usually large) number of amino acid s by peptide links (–NH–CO–).

- gastric inhibitory p. (GIP) a peptide hormone secreted by the stomach; GIP inhibits the secretion of acids and of pepsin and stimulates insulin release as part of the digestive process. SYN: gastric inhibitory peptide.

- glucose-dependent insulinotropic p. an insulinotropic substance originating in the gastrointestinal tract and released into the circulation following ingestion of a meal containing glucose.

- pancreatic p. 1. a 36-amino acid peptide secreted by islet cells of the pancreas in response to a meal and of uncertain physiologic function; 2. a family of gastrointestinal peptides, which includes pancreatic p., neuropeptide Y, and peptide YY.

- trefoil p. a group of polypeptides that share the trefoil moiety of a highly stable three-loop structure held together by disulfide bonds based on cysteine residues; they are widely expressed in gastrointestinal tissues and secreted by mucous cells; their functions are as yet unknown.

- vasoactive intestinal p. (VIP) a p. hormone secreted most commonly by non-β islet cell tumors of the pancreas; VIP increases the rate of glycogenolysis and stimulates pancreatic bicarbonate secretion; excess production causes copious watery diarrhea and fecal electrolyte loss, with hypokalemia and hypochlorhydria. SYN: vasoactive intestinal peptide.

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poly·pep·tide .päl-i-'pep-.tīd n a molecular chain of amino acids

poly·pep·tid·ic -(.)pep-'tid-ik adj

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n.

a molecule consisting of three or more amino acids linked together by peptide bonds. protein molecules are polypeptides.

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poly·pep·tide (pol″e-pepґtīd) [poly- + peptide] a peptide that on hydrolysis yields more than two amino acids; called tripeptides, tetrapeptides, and so on according to the number of amino acids contained. See also peptide.