title: Hydrolysis of succinyl-trialanine p-nitroanilide by two enzymes associated with human high-density lipoproteins.
abstract: Succinyl-trialanine p-nitroanilide (Suc-Ala3-pNA), a synthetic substrate for the determination of elastase activity, was hydrolyzed in sequence by two enzymes that were found to be associated with human high-density lipoproteins. The enzymes involved in the sequence of reaction were separated by ion-exchange chromatography from apo-lipoprotein A-I and A-II, major apoproteins of high-density lipoproteins. One, designated as fraction MK, cleaves Suc-Ala3-pNA to succinyl-dialanine and alanine p-nitroanilide (Ala-pNA), and the other, designated as fraction U, cleaves Ala-pNA to alanine and p-nitroaniline. Fraction MK was inhibited by dithiothreitol, EDTA, and 1,10-phenanthroline, whereas fraction U was inhibited by 1,10-phenanthroline and bestatin. In addition to these findings, fraction MK also hydrolyzed 2,4-dinitrophenyl-prolyl-glutaminyl-glycyl-isoleucyl-alanyl-glycyl-glutaminyl- arginine (DNP-octapeptide), a specific substrate for the determination of vertebrate collagenase. Neither native elastin nor native collagen was hydrolyzed by a mixture of the two enzymes. Fraction U was very similar to aminopeptidase M with respect to its enzyme characteristics studied.
mesh_terms: D006801:Humans; D006868:Hydrolysis; D007527:Isoenzymes / Q000097:blood / Q000302:isolation & purification; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood* / Q000302:isolation & purification; D008970:Molecular Weight; D009842:Oligopeptides / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000097:blood* / Q000302:isolation & purification; D013379:Substrate Specificity
chemical_list: D007527:Isoenzymes; D008075:Lipoproteins, HDL; D009842:Oligopeptides; C015516:succinyl-trialanine-4-nitroanilide; D010447:Peptide Hydrolases; C023092:succinyltrialanine p-nitroanilide hydrolase