PURIFICATION AND SOME PROPERTIES OF A PROTEASE FROM STREPTOMYCES-LIMOSUS

Streptomyces limosus was selected because it secreted a novel protease that catalyzed the synthetic reaction forming Pro-Pro-Pro from Pro-Pr o. The protease was purified to an electrophoretically homogeneous sta te and an activity of more than about 20,000-fold that of the culture broth. The molecular mass of the enzyme was estimated to be 50 kDa by SDS-polyacrylamide gel electrophoresis. The enzyme was most active in alkaline pH for the synthetic reaction producing Pro-Pro-Pro from Pro- Pro, although for the hydrolytic reaction forming proline it was most active in neutral pH. The enzyme was inhibited by 1,2-epoxy-3-(p-nitro phenoxy)propane (EPNP) and diazoacetyl-DL-norleucine methyl ester (DAN ). It can be considered that this enzyme belongs to the class of aspar tic proteases. The substrate specificity indicates that this enzyme ha s a strong affinity for proline as a N-terminal amino acid of peptides .