Characterization of a keratinolytic serine protease from Bacillus subtilis KS-1

A keratinolytic enzyme produced by Bacillus subtilis KS-1 isolated from poultry waste was purified and characterized using ultrafiltration, DEAE-Sephadex, and Sephadex G-100 chromatographies. The specific activity of the purified protease was 538.2 units/mg. The enzyme was shown to have a relative molecular mass of 25.4 kDa. The enzyme was made completely inactive by PMSF, which indicates a serine-protease. Dithiothreitol enhanced keratinolytic activity by 1.6 times at a concentration of 5.0 mM. These results suggest that the cleavage of the disulfide bonds with reducing agents can occur directly or by excretion of sulfite, which causes the sulfitolysis of the disulfide bonds. The first 10 amino acids of the N-terminal sequence are Ala-Gin-Pro-Val-Glu-Trp-Gly-Ile-Ser-Gln. The enzyme hydrolyzed casein and feather, but hydrolyzed casein more effectively than it did feather.