Partial Characterization of an Acidic Protease from Rhizopus stolonifer RN-11

The present study characterises an acidic protease purified from the Rhizopus stolonifer strain, RN-11. The acidic protease with a 70 kDa molecular weight, was stable within pH 2-4 at temperatures 40-50°C. The temperature and pH value conducive to optimal catalytic activity were pH 2.5 and 50°C, respectively. Treatment with 5 mmol metal ions showed that the acidic protease was activated by Na, K, Mn, Cu and Ca, inhibited by Zn, Li and Fe, and unaffected by Mg. It was proposed that the studied acidic protease might represent a previously uncharacterised type of acidic protease produced by the Rhizopus stolonifer RN-11 strain.