Purification and characterization of thermostable α-amylase II from Bacillussp- JF2 strain

Abstract

Thermostable α-amylase from Bacillus sp- JF 2 strain was found to have three active components (names α-amylase I, II, and III) with molecular weights of 110,000, 140,000, and 300,000, respectively. α-Amylase II was isolated and purified in the current work by different procedures from that for α-amylase I. α-Amylase II consists of two identical subunits (MW 70,000). The isoelectric point is 4.7. The temperature optimum is at 90°C and the pH optimum is 5.5. for the enzyme activity. The half-life of the enzyme at 90°C is 30 min, and the enzyme is stable over a pH range of 7.0–9.0. The K m value of the enzyme was estimated to be 3.3 mg ml −1. A considerable difference in amino acid composition was observed between α-amylase I and α-amylase II. The α-helix content of α-amylase II was calculated to be 51% from the circular dichroism spectrum. The number of Ca 2+ binding to each molecule of α-amylase II was determined to be 10 by atomic adsorption.