polypeptide Biochem.
(pɒlɪˈpɛptaɪd)
[ad. G. polypeptid (E. Fischer 1903, in Sitzungsber. d. k. preuss. Akad. d. Wissensch. 389, after di-, tripeptid, etc. (Fischer 1902: see peptide)).]
Any peptide in which the number of amino-acid residues that go to make up the molecule is not small (cf. oligopeptide s.v. oligo-), but is not so large that it can be regarded as a protein; polypeptide chain = peptide chain s.v. peptide 2.
| 1903 Jrnl. Chem. Soc. LXXXIV. i. 466 These acid chlorides combine easily with glycylglycine esters and similar compounds to form chains of amino-acids joined together by an anhydride linking. Such are termed polypeptides. 1935 R. H. A. Plimmer in Harrow & Sherwin Textbk. Biochem. v. 177 Fischer held the view that the polypeptide chain was not long enough for attack by pepsin. 1949 H. W. Florey et al. Antibiotics I. i. 38 The active preparation made from this organism.. contains two antibiotics, gramicidin and tyrocidine, both crystalline polypeptides. 1951 New Biol. XI. 99 Larger molecules that show biological activity when applied to living organisms are exemplified by polypeptides, such as A.C.T.H. (the pituitary hormone which controls the secretion of cortisone). 1959 Times 2 Jan. 11/3 Further evidence suggested that this particular polypeptide was a precursor of the cell wall of the staphylococcus. 1961 Ann. Reg. 1960 401 The polypeptide chain, the backbone of the protein molecule, was found to be coiled in a helix-like spiral spring with only a space inside. 1978 Sci. Amer. Dec. 68/2 A hemoglobin molecule is made up of four polypeptide chains, two alpha chains of 141 amino acid residues each and two beta chains of 146 residues each. |
Hence polyˈpeptidase [-ase], any enzyme which hydrolyses polypeptides.
| 1922 Chem. Abstr. XVI. 3491 (heading) Influence of materials obtained from yeast cells and organs on the rate of hydrolysis of substrates by polypeptidases, carbohydratases and esterases. 1929 R. P. Walton tr. Waldschmidt-Leitz's Enzyme Actions 159 The yeast polypeptidases are totally inactive against dipeptides. 1940, 1961 [see erepsin]. |