Purification and some properties of porcine liver aminopeptidase B

An aminopeptidase B from porcine liver was purified about 2,000-fold by ammonium sulfate fractionation and a series of chromatographies on hydroxyapatite, DEAE-cellulose, Sephadex G-150, hydroxyapatite and DEAE-Sepharose columns. The purified preparation was homo geneous on polyacrylamide gel electrophoresis. The molecular weight of the enzyme was about 58,000 as determined by gel filtration on Sephadex G-100 and disc gel electrophoresis in the presence of sodium dodecyl sulfate. The enzyme exhibited maximum activity at pH 7.5 for the hydrolysis of L-arginine β-naphthylamide at 25°C. The enzyme was labile to prolonged warming and freezing. The enzyme was markedly stimulated by chloride ion, and was inhibited by Cu2+ Zn2+, Cd2+ Hg2+, Pb2+ and metal chelating agents. p-Chloromercuribenzoate was an uncompetitive inhibitor of the enzyme with a K1 value of 1.8 × 102−M. The enzyme was ini by 1,10-phenanthroline, and the inhibition was of the mixed type with a K1 value of 1.9 × 10−4 M but activity was restored by the addition of Zn2+, Co2+, and Fe2+