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A Novel α-Glucosidase of the Glycoside Hydrolase Family 31 from Aspergillus sojae
Authors:Atsushi Kawano  Yuji Matsumoto  Nozomi Nikaido  Akihiro Tominaga  Takashi Tonozuka  Kazuhide Totani  Nozomu Yasutake
Affiliation:1. RD&E Center, Showa Sangyo Co., LTD. ;2. Division of Chemical Engineering and Biotechnology, Department of Engineering for Future Innovation, National Institute of Technology, Ichinoseki College ;3. Department of Applied Biological Science, Tokyo University of Agriculture and Technology
Abstract:We characterized an α-glucosidase belonging to the glycoside hydrolase family 31 from Aspergillus sojae. The α-glucosidase gene was cloned using the whole genome sequence of A. sojae, and the recombinant enzyme was expressed in Aspergillus nidulans. The enzyme was purified using affinity chromatography. The enzyme showed an optimum pH of 5.5 and was stable between pH 6.0 and 10.0. The optimum temperature was approximately 55 °C. The enzyme was stable up to 50 °C, but lost its activity at 70 °C. The enzyme acted on a broad range of maltooligosaccharides and isomaltooligosaccharides, soluble starch, and dextran, and released glucose from these substrates. When maltose was used as substrate, the enzyme catalyzed transglucosylation to produce oligosaccharides consisting of α-1,6-glucosidic linkages as the major products. The transglucosylation pattern with maltopentaose was also analyzed, indicating that the enzyme mainly produced oligosaccharides with molecular weights higher than that of maltopentaose and containing continuous α-1,6-glucosidic linkages. These results demonstrate that the enzyme is a novel α-glucosidase that acts on both maltooligosaccharides and isomaltooligosaccharides, and efficiently produces oligosaccharides containing continuous α-1,6-glucosidic linkages.
Keywords:α  -glucosidase  Aspergillus  glycoside hydrolase family 31  transglucosylation
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