Purification and Some Properties of Acid-stable α-Amylases from Shochu koji (Aspergillus kawachii)

抄録

Aspergillus kawachii α-amylase [EC 3.2.1.1] 1 and II were purified from shochu koji extract by DEAE Bio-Gel A ion exchange chromatography, Sephacryl S-300 gel chromatography (pH 3.6), ω-amino dodecyl agarose column chromatography and Sephacryl S-200 gel chromatography. By gel chromatography on a Sephacryl S-300 column, the molecular weights of the purified α-amylase I and II were estimated to be 104, 000 and 66, 000, respectively. The isoelectric points of α-amylase I and II were 4.25 and 4.20, respectively. The optimal pH range of α-amylase I was 4.0 to 5.0, and the optimum pH of α-amylase 'II was 5.0. The optimum temperatures of both α-amylases were around 70°C at pH 5.0. Both α-amylases were stable from pH 2.5 to 6.0 and up to 55°C, retaining more than 90% of the original activities. Heavy metal ions such as Hg²⁺ and Pb²⁺ were potent inhibitors for both α-amylases.