Role of the Carbohydrate Moiety of a Glucoamylase from Aspergillus awamori var.kawachi in the Digestion of Raw Starch

概要

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The digestion of raw starch by a glucoamylase (GA MU-H) from a mutant strain of Aspergillus awamori var. kawachi was closely correlated with mannoside chains O-linked to the Gp-I region (A^<470>-V^<514>), but not sugar chains N-linked to catalytic GAI' domain of GA MU-H. The partial replacement of mannose residues by glucose residues led to a significant decrease raw starch digestion. By the substitution of D_20 for H_20 in the reaction mixture, the raw starch digestion of GA MU-H decreased to 80% of that at 30℃, although the rate of hydrolysis of soluble starch by and the ability to bind β-cyclodextrin of GA MU-H were unchanged. Glycerol, known as an antichaotropic reagent, decreased the raw starch digestion of GA MU-H significantly. However, it did not have any effect on the enzymatic activity for soluble starch when soluble starch was the substrate. The efficient digestion of raw starch with raw starch-digesting glucoamylase needed the mannoside chains O-linked to the Gp-I region, which were suggested to contribute to digestion of raw starch through the interaction with water.
社団法人日本農芸化学会の論文
1995-01-23