Abstract

The alkaline protease of Xanthomonas sp. YL-37 has been purified, and the properties of the enzyme investigated. The alkaline protease of Xanthomonas sp. YL-37 was purified form crude enzyme by ammonium sulfate fractionation, CM-cellulose ion exchange chromatography, and Sephadex G-100 gel filtration. Through the series of chromatographies, the enzyme was purified to homogenecity with specific activity of 4.23 fold higher than that of the crude broth. The molecular weight of the purified protease has been estimated to be 62 KDa on SDS-polyacrylamide gel electrophoresis. The optimal pH and temperature for alkaline protease activity were 11.0 and 50℃, respectively. The enzyme was stable between pH 5.0 and 10.0 and up to 50℃. Enzyme activity was lost up to 50% on heating at 70℃ for 30 minutes. The activity of alkaline protease was inhibited by Cu^2+, Zn^2+, Hg^2+, PMSF, and activated by Mn^2+ and Ca^2+. The K_m value for casein as a substrate was 4.0 mg/ml.

• Keywords: Xanthomonas sp. YL-37; alakaline protease