Characteristics of an aminopeptidase activity from the cultural fluid of Bacillus subtilis

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Abstract
An aminopeptidase activity of the cultural fluid of Bacillus subtilis readily hydrolyzed L-leucyl-β-naphthylamide after preincubation with Co(NO3)2. Numerous other divalent metal ions did not activate the enzyme toward LNA but were found to inhibit enzyme activation by cobalt ions. Other aminopeptidase substrates were hydrolyzed by the native enzyme, cobalt activated native enzyme and cobalt, or zinc activated EDTA-treated enzyme. The aminopeptidase activity of cultural fluids was stable at 70° for at least 2 h; however, EDTA-treated enzyme was not stable under identical conditions. Reactivation of EDTA-treated enzyme with cobalt or zinc ions restored partial and complete heat stability, respectively, while calcium reactivated enzyme was heat labile. Enzymatic activity toward LNA substrate was lost on the removal by dialysis of excess cobalt ions indicating that metal ions play at least a bifunctional role, one relating to structural stability and one relating to enzymatic activity.

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