Studies on an alpha-amylase from a thermophilic bacterium. I. Purification and characterization

An amylase-producing thermophilic bacterium was isolated from a Japanese hot spring. The thermophilic cells were gram-negative, nonsporulating, nonpigmented rods and were motile with flagella. Alpha-Amylase [EC 3.2.1.1) purified from the thermophile was studied. The enzyme was more heat-stable than the corresponding enzymes from mesophilic sources, and 50% loss of activity was observed after incubation for 1 hr at 90 degrees. The thermophilic enzyme resembled the corresponding mesophilic enzymes in many respects, such as kinetic parameters, physicochemical properties, and amino acid composition. The molecular weight of the enzyme was 50,000 and the enzyme contained 2 moles of half-cystine residues per mole of protein, but there were no disulfide crosslinkages. The alpha-helix content of the enzyme was estimated to be about 20% from CD spectra, a value similar to those of other alpha-amylases. The isoelectric point of the enzyme was at pH 9.2.