Studies on Bacterial Protease

Part XVIII. Proteolytic Specificity of Neutral Protease of Bacillus subtilis var. amylosacchariticus

Abstract

Substrate specificity of the crystalline neutral protease of B. amylosacchariticus was investigated using the B-chain of oxidized beef insulin as the substrate, and the results were compared with those of proteases obtained from other strains of Bacillus subtilis. The neutral protease split the B-chain at eleven sites of the peptide linkages, indicating the narrow specificity as compared with subtilopeptidase A. The results also indicated that the peptide bonds susceptible to the action of the neutral protease were mainly those involving amino group of hydrophobic amino acids and tyrosine, with a few exception. The enzyme showed potent activities in casein digestion at near neutrality and in milk clotting at pH 5.6, whereas it was completely inert on esters and keratin, and only slightly active toward elastin.