Abstract
A novel amylase, which hydrolyzes both pullulan and soluble starch at the same rate, was found in the culture filtrate of Bacillus circulans F-2. The enzyme was purified by ammonium sulfate fractionation, starch adsorption, and ion-exchange and hydrophobic chromatographies. The purified enzyme showed a single protein band on polyacrylamide gel electrophoresis both in denatured and non-denatured conditions and activity bands toward soluble starch and pullulan comigrated on the gel. The molecular weight of the enzyme was determined to be 220 000 by gel filtration. Its isoelectric point was found to be 4.13. The optimum pH of amylase activity were determined to be around 7.0–8.5, while that of the pullulanase activity was around 7.0. The optimum temperature of both enzymes was about 50°C. The enzyme produced a series of maltooligosaccharides from amylase whereas it produced only maltotriose (G 3) from pullulan. It was found that this enzyme possessed two active sites to hydrolyze α-1,4-glucosidic and α-1,6-glucosidic linkages with the same rate.
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