Studies on Mold Proteases

The substrate specificity of the crystalline acid protease obtained from Rhizopus chinensis was determined using B-chain of oxidized beef insulin and numerous synthetic peptides, comparing with that of several acid proteases from various sources. The peptide bonds susceptible to the action of Rhiz. acid protease were found to be mainly those involving the amino group of bulky amino acids. The enzyme split the B-chain of oxidized insulin at twelve sites of the peptide linkages and a certain similarity in the specificity was observed among the three acid proteases, Rhiz. protease, rennin and pepsin, all of which were known to show potent milk clotting activities.