title: Purification and characterization of an aminopeptidase from porcine liver.
abstract: An aminopeptidase was purified about 700-fold from porcine liver homogenate by ammonium sulfate fractionation and a series of column chromatographies on DEAE-cellulose, Sephadex G-150, DEAE-Sepharose, and hydroxyapatite. The purified enzyme had a specific activity of 4.6 mumol X min-1 X mg-1 using L-leucine beta-naphthylamide as the substrate. The molecular weight of the enzyme was about 96,000 as determined by Sephadex G-150 column chromatography. The enzyme had a broad specificity and a pH optimum between 6.5 and 7.0 for hydrolysis of alpha-aminoacyl-beta-naphthylamines, and it hydrolyzed the beta-naphthylamides of aliphatic, basic, and aromatic amino acids. The enzyme also hydrolyzed peptide substrates with phenylalanine residues as their amino-termini, but it did not hydrolyze L-phenylalanyl-L-proline. The enzyme was inhibited by metal-chelating agents, sulfhydryl reagents, heavy metals, bestatin, and puromycin. Activity of the enzyme inhibited by sulfhydryl-reactive reagents was restored by the addition of sulfhydryl compounds. The enzyme was activated by cobaltous ion and the values of both Km and Vmax increased. The activation was pH-dependent and above pH 7.5 cobalt ion behaved as an inhibitor of the enzyme. No metal ions other than cobaltous ion stimulated the enzyme appreciably.
mesh_terms: D000626:Aminopeptidases / Q000037:antagonists & inhibitors / Q000302:isolation & purification*; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D003035:Cobalt / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology*; D013552:Swine
chemical_list: D003035:Cobalt; D000626:Aminopeptidases