Studies on Mold Dextranases
IV. Substrate Specificity of Aspergillus carneus Dextranase
1972 年 71 巻 4 号 p. 653-660
詳細
1972 年 71 巻 4 号 p. 653-660
Substrate specificity of the dextranase [α-1, 6-glucan 6-glucanohydrolase, EC 3. 2. 1. 11] of Aspergillus carneus was investigated using a series of isomaltodextrins, dextran and their derivatives as the substrates. The enzyme readily hydrolyzed dextran T-2000 which consisted of more than 95% of α-1, 6-glucosidic linkage, giving rise to isomaltotriose, isomaltose and a small amount of glucose together with traces of higher oligomers, the degree of hydrolysis being about 40%. Dextran IAM that contained 66% of α-l, 6-glucosidic linkage was hydrolyzed by the enzyme very slowly and to a lesser extent. Among a series of isomaltodextrins tested, G4 to G8 com-pounds were split into isomaltose and isomaltotriose at a rate comparable with that of hydrolysis of dextran T-2000. The enzyme attacked isomaltotriose at an extremely slow rate and did not act on isomaltose. Comparison of the enzymatic digestion products from isomaltodextrins and their reduced derivatives (sugar alcohols) suggests that the enzyme removes primarily isomaltotriosyl unit and, to somewhat lesser extent, isomaltosyl unit from the nonreducing end of isomaltodextrins. Synthetic reaction was observed by incubation of the enzyme with high concentration of iso-maltose and of isomaltotriose but not from glucose.
