Purification and some properties of porcine liver aminopeptidase B

Abstract

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 homogeneous 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 beta-naphthylamide at 25 degrees 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 Ki value of 1.8 X 10(-6) M. The enzyme was inhibited by 1,10-phenanthroline and the inhibition was of the mixed type with a K1 value of 1.9 X 10(-4) M but activity was restored by the addition of Zn2+, Co2+, and Fe2+.