Alkaline serine protease was purified to homogeneity from culture supernatant of a thermophilic, alkaliphilic Bacillus sp. by 80% ammonium sulphate precipitation followed by CM-cellulose and DEAE-cellulose ion exchange column chromatography. The enzyme was purified up to 16.5-fold with 6900 U/mg activity. The protease exhibited maximum activity towards casein at pH 8.0 and at 80 °C. The enzyme was stable at pH 8.0 and 80 °C temperature up to 2 h. The Ca2+ and Mn2+ enhanced the proteolytic activity up to 44% and 36% as compared to control, respectively. However, Zn2+, K+, Ba2+, Co2+, Hg2+ and Cu2+ significantly reduced the enzyme activity. PMSF (phenyl methyl sulphonyl fluoride) completely inhibited the protease activity, whereas the activity of protease was stimulated up to two folds in the presence of 5 mM 2-mercaptoethanol. The enzyme was also stable in surfactant (Tween-80) and other commercial detergents (SDS, Triton X-100).
Kamran, A., Ur Rehman, H., Ul Qader, S. A., Baloch, A. H., & Kamal, M. (2015). Purification and characterization of thiol dependent, oxidation-stable serine alkaline protease from thermophilic Bacillus sp. Journal of Genetic Engineering and Biotechnology, 13(1), 59–64. https://doi.org/10.1016/j.jgeb.2015.01.002