CHARACTERIZATION OF A SMALL METALLOPROTEASE FROM STREPTOMYCES-CAESPITOSUS WITH HIGH SPECIFICITY TO AROMATIC RESIDUES

A zinc metalloendoprotease from Streptomyces caespitosus (ScNP) is one of the smallest proteases found to date. It consists of a single poly peptide chain of 132 amino acid residues with a molecular weight of ab out 15 kDa. According to the amino acid sequence, this protease was cl assified in the Streptomyces small neutral protease family with an asp artate (Asp93) as a metal-binding site. We have determined the cleavag e specificities and the optimal conditions for hydrolysis. The amino-t erminal amino acid sequences of the hydrolyzed products of an oxidized insulin B-chain showed a high specificity to aromatic residues such a s phenylalanine and tyrosine. The enzyme showed maximal activity again st azocasein at pH 6.0 and 50 degrees C. ScNP was inhibited by EDTA an d 1,10-phenanthroline. Our studies indicated that ScNP is the smallest metalloendoprotease which hydrolyzes with high specificity and this s pecificity of ScNP was compared with those of ether metalloendoproteas es.