Purification and Characterization of Bacillus Licheniformis ￥á-Amylase from Genetically Cloned E. coli NM522

摘要

Bacillus licheniformis メ-amylase cloned in E. coli genetically was purified by ammonium sulfate fractionations, DEAE-Sephacel, Mono-S, and Superose-6 column chromatographies. The highly purified メ-amylase preparation showed 221.8 units per mg protein with 30% yield. Disc gel electrophoresis showed one major protein band. The molecular weight of B. licheniformis メ -amylase produced in E. coli was 55,000 daltons by SDS gel electrophoresis. The Km value of Bacillus licheniformis メ-amylase produced in E. coli was 0.22% and the Vmax of the enzyme was 0.6-0.7% min by Hofstee plot. The activity of enzyme showed maximum through wide range of pH, from pH 4 to pH 8 but slowly decreased with increasing pH values. The enzyme required Ca2+ for its activity. At pH 8.0, the enzyme had about 25% activity after 15 min incubation at 90∩ with 1 mM Ca2+.