Abstract
The gene encoding an intracellular α-amylase, AmyB (TM1650), from Thermotoga maritima MSB8, a hyperthermophilic bacterium, was cloned and expressed in Escherichia coli. The AmyB enzyme hydrolyzed α-1,4 starch linkage. The amyB gene is 1269 bp in length, encoding a protein of 422 amino acids (calculated molecular mass of 50 187 Da). The molecular weight of the enzyme was estimated to be 50 000 Da by SDS-PAGE after starch-nondenaturing-PAGE. The amino acid sequence of AmyB showed less than 12% identity to other amylases, but contained four regions that are highly conserved among α-amylases. The AmyB α-amylase exhibited maximal enzymatic activity at pH 7.0 and its optimum temperature for activity was 70 °C. Like the α-amylases of many other organisms, the thermostability of T. maritima MSB8 α-amylase, AmyB expressed in E. coli was enhanced in the presence of Ca 2+ (10 mM).
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