Purification and characterization of aminopeptidase B from goat brain

Aminopeptidase B was purified from goat brain with a purification fold of ∼280 and a yield of 2.7%. The enzyme revealed a single band on both native acrylamide gel and SDS-PAGE thereby confirming apparent homogeneous preparation and its monomeric nature. The enzyme exhibited a molecular mass of 80.2 kDa and 79.7 kDa on Sephadex G-200 and SDS-PAGE respectively. The pH optimum was 7.4 and the enzyme was stable between pH 6.0 and 9.0. l-Arg-βNA was the most rapidly hydrolyzed substrate followed by Lys-βNA. The Km value with Arg-βNA was found to be 0.1 mM. Metal chelating and –SH reactive agents strongly inhibited the enzyme activity. 1,10-Phenanthroline exhibited mixed type of inhibition with a Ki of 5 × 10−5 M. The enzyme was highly sensitive to urea. Metal ions like Ni2+, Cd2+, Fe2+and Hg2+ inhibited the enzyme, whereas Co2+, Zn2+, Mn2+and Sn2+ slightly activated the enzyme.