Aeromonas Aminopeptidase

Abstract

The extracellular aminopeptidase of Aeromonas proteolytica was purified to homogeneity by a simplified procedure that proved feasible for the isolation of gram quantities of this enzyme. Precipitation with ammonium sulfate and acetone, heating at 70°, and chromatography on Sephadex G-75 and DEAE-Sephadex yielded a product that showed a high degree of purity by polyacrylamide and free boundary electrophoresis over a wide range of pH values, and by immunoelectrophoresis, ultracentrifugation, chromatography, and assay for endopeptidase. Yields as high as 70%, representing 170-fold purification, were obtained by the isolation procedure. The enzyme was isoelectric near pH 3.0, a value that reflected the high ratio of acidic to basic residues found by amino acid analysis. Sedimentation equilibrium and sedimentation velocity measurements yielded molecular weight values of 28,480 and 29,500, respectively, and experiments on the stoichiometry of zinc to apoenzyme suggested that the aminopeptidase binds 2 g atoms of zinc per mole.