Bacillus subtilis aminopeptidase: Purification, characterization and some enzymatic properties

The extracellular aminopeptidase from Bacillus subtilis was purified 300-fold by a simple procedure which gave a high recovery of enzyme. The native enzyme was shown to be a monomer of molecular weight 46,500 and to contain 1 g-atom of Zn 2+ per mole of protein. Amino acid analyses demonstrated the protein to be rich in acidic residues and Lys, to possess about 3 residues of Met, and to be devoid of Cys. When activated with 5 m m Co(NO 3) 2 for 90 min the activity of the native enzyme was increased; the amount of activation depended on the identity of the substrate. Cobalt activation involved the reversible binding of 1 g-atom of Co 2+ per mole of protein, without displacing the native Zn 2+; K Co was 1.25 m m. Zinc ions competed with Co 2+ during activation, a process characterized by a K Zn of 28 μ m. Ions other than Co 2+ did not appreciably activate the enzyme.