A Bacillus acidocaldarius .ALPHA.-amylase that is highly stable to heat under acidic conditions.

Abstract

An extracellular amylase of B. acidocaldarius, strain A-2, was purified as an electrophoretically homogeneous protein, and the properties of the purified enzyme were examined. This enzyme behaved like α-amylase (1, 4-α-D-glucan glucanohydrolase, EC 2.3.1.1). Its molecular weight, Km value, and optimum reaction temperature and pH were 66, 000, 1.6mg starch/ml, and 70°C and 3.5, respectively. More than 70 and 90% of the initial activity remained after 30 min of incubation at pHs 2.0 (70°C) and 4.5 (90°C) in the absence of substrate. The thermal stability under acidic conditions is better than that of other B. acidocaldarius α-amylases reported to date.