Keratinase of Doratomyces microsporus

The fungus Doratomyces microsporus produced an extracellular keratinase dur ing submerged aerobic cultivation in a medium containing a protein inducer for enzyme synthesis. The keratinase was purified to homogeneity using hydr ophobic interaction chromatography followed by gel chromatography. The mole cular weight was estimated to be 33 kDa (from SDS-PAGE analysis) or 30 kDa (by gel chromatography), suggesting a monomeric structure. The isoelectric point of the enzyme was determined to be around 9. The optimal pH and tempe rature for keratinolytic activity were pH 8-9 and 50 degrees C, respectivel y. The serine protease inhibitor PMSF totally inhibited the keratinase. The enzyme was not glycosylated. It was capable of hydrolysing different kerat inous materials as well as some non-keratinous proteins. Hydrolysis of some synthetic substrates, specific for known proteinases, suggested that the k eratinase of D. microsporus is close to proteinase K.