Cloning, Heterologous Expression and Characterization of an Intracellular Serine Protease from Bacillus sp. LCB10

An intracellular serine protease designated ISPr from newly isolated salt-tolerant Bacillus sp. LCB10 was expressed in Escherichia coli. The isp gene was cloned into pET30a vector and expressed in E. coli BL21 (DE3). After purification, the molecular mass of ISPr was estimated to be 35 kDa by SDS-PAGE and the specific activity was 384 U/mg. The protease showed optimal activity at 40 degrees C and pH 10.0. ISPr was active and stable in wide range of alkaline pH. ISPr activity increased 1.8-fold in the presence of Mn2+ and was completely inhibited by PMSF. The enzyme exhibited high NaCl tolerance. The protease had a stable activity in the presence of 1-5% NaCl and retained 86% activity in the presence 7% NaCl, thus, this enzyme would have great potential in industry.