Studies on Thermophilic α-Amylase from Bacillus stearothermophilus

Abstract

The effects of pH, urea and EDTA on the thermal stability of thermophilic α-amylase [EC 3.2.1.1] were studied by the measurements of enzymatic activity and optical activity in the far ultraviolet region at various temperatures. Thermophilic α-amylase became unstable by removing calcium and protected against an inactivation in the presence of saturation level of calcium. Thermal stability of the enzyme was affected by 10^–2M EDTA than 8 M urea. This was more remarkable in thermophilic α-amylase than in B. subtilis α-amylase. These results suggested that calcium ion plays an important role in thermal stability of thermophilic α-amylase molecule. In the presence of 8 M urea, thermophilic α-amylase scarcely showed an alteration on the CD spectrum at room temperature, although the presence of 8 M urea promoted the dena-turation of thermophilic α-amylase at the elevated temperature.