Purification and characterization of a keratinolytic serine proteinase from Streptomyces albidoflavus

Streptomyces strain. K1-02, which was identified as a strain of Streptomyce s albidoflavus, secreted at least six extracellular proteases when it was c ultured on feather meal-based medium. The major keratinolytic serine protei nase was purified to homogeneity by a two-step procedure. This enzyme had a molecular weight of 18,000 and was optimally active at pH values ranging f rom 6 to 9.5 and at temperatures ranging from 40 to 70 degrees C. Its sensi tivity to protease inhibitors, its specificity on synthetic substrates, and its remarkably high level of NH2-terminal sequence homology with Streptomy ces griseus protease B (SGPB) shelved that the new enzyme, designated SAKas e, was homologous to SGPB. We tested the activity of SAKase with soluble an d fibrous substrates (elastin, keratin, and type I collagen) and found that it was very specific for keratinous substrates compared to SGPB and protei nase K.