An aminopeptidase activity from porcine kidney that hydrolyzes oxytocin and vasopressin: purification and partial characterization.

Abstract An aminopeptidase from porcine kidney, hydrolyzing oxytocin and vasopressin in vitro, was purified by chromatography on hydroxyapatite, DEAE-cellulose and nickel ion chelate gel and gel filtration on Sephadex G-100. The enzyme appeared to be a high molecular mass ( M r 105 000) monomeric protein. It was sensitive to inhibition by metal chelator, o -phenanthroline. Cobalt ion and sulfhydryl activator, 2-mercaptoethanol, had activating effects, while p -chloromercuribenzoate, amino acids with large hydrophobic side chains, l -cystine and aminopeptidase inhibitors, bestatin and amastatin, had inhibitory effects on the enzyme activity. The enzyme hydrolyzed several aminoacyl p -nitroanilides, and had the highest specificity against S- benzyl- l -cysteine p -nitroanilide. The properties of the enzyme were distinct from those of well-characterized leucyl aminopeptidase (EC 3.4.11.1), membrane alanyl aminopeptidase (EC 3.4.11.2) and primate placental cystinyl aminopeptidase (EC 3.4.11.3).