Rabbit kidney aminopeptidases: purification and some properties

Aminopeptidases (EC.3.4.11...) are widely distributed in nature and have medical and biological importance due to their function in the modification and degradation of protein. Two aminopeptidases were purified from rabbit kidney homogenate by ion exchange and gel filtration chromatography columns, using aminoacyl of beta-naphthylamides and p-nitroanilides as substrates. The enzymes' homogeneity was assured by SDS-PAGE. The first enzyme (P1) has an optimum of pH 7.0, a molecular mass of 70 kDa, best catalytical efficiency for methionyl-beta-naphthylamide, is 70% inhibited by 0.5 mM Zn2+ and Co2+ ions, 3.33 mM sodium hydrocortisone succinate and 0.08 mM p-hydroxymercuribenzoate, and is little or not inhibited by EDTA, amino acids, p-nitroaniline, beta-naphthylamine, deoxicholate, bestatin and puromycin. The second enzyme (P2) has an optimum of pH 7.0, a molecular mass of 54 kDa, best catalytical efficiency for Leu-beta-naphthylamide, is inhibited by 0.5 mM ions Zn2+ (45%), 0.02 mM EDTA (94%) 0.08 mM p-hydroxymercuribenzoate (70%), 3.33 mM beta-ME (13%), 1.33 mM p-nitroaniline (40%), 1.33 mM beta-naphthylamine (17%), 1.33 mM sodium deoxicholate (96%), 3.33 mM sodium hydrocortisone succinate (60%), and is 30% activated by 0.5 mM Co2+ ions. Puromycin and bestatin are competitive inhibitors with Ki values in 10(-6) and 10(-7) M order, respectively. P1 is a methionine aminopeptidase, while P2 is a leucine aminopeptidase.