A THERMOSTABLE, ALKALINE-ACTIVE, KERATINOLYTIC PROTEINASE FROM CHRYSOSPORIUM-KERATINOPHILUM

Thermostable alkaline proteinase was produced by a strain of Chryosoporium keratinophilum when cultured in lactose/mineral salt medium incorporating keratin solubilized with DMSO. The proteinase, partially purified by cold-acetone precipitation followed by gel-filtration on Sephadex G-75, was optimally active at pH 9 and stable from pH 7 to 10 with over 90% relative residual activity after incubation at 25-degrees-C for 24 h. The optimum temperature for enzyme activity was 90-degrees-C at which the activity half-life was 30 min. Enzyme activity was stimulated by Fe2+ and inhibited by 1,10 o-phenanthroline. Gel-filtration indicated an M(r) of 69 kDa.