CHARACTERIZATION OF A KERATINOLYTIC SERINE PROTEINASE FROM STREPTOMYCES-PACTUM DSM-40530

A serine protease from the keratin-degrading Streptomyces pactum DSM 4 0530 was purified by casein agarose affinity chromatography. The enzym e had a molecular weight of 30,000 and an isoelectric point of 8.5. Th e proteinase was optimally active in the pH range from 7 to 10 and at temperatures from 40 to 75 degrees C. The enzyme was specific for argi nine and lysine at the P-1 site and for phenylalanine and arginine at the P-1' site. It showed a high stereoselectivity and secondary specif icity with different synthetic substrates. The keratinolytic activity of the purified proteinase was examined by incubation with the insolub le substrates keratin azure, feather meal, and native and autoclaved c hicken feather downs. The S. pactum proteinase was significantly more active than the various commercially available proteinases. After incu bation with the purified proteinase, a rapid disintegration of whole f eathers was observed. But even after several days of incubation with r epeated addition of enzymes, less than 10% of the native keratin subst rate was solubilized. In the presence of dithiothreitol, degradation w as more than 70%.