Aspergillus awamori の α-D-glucosidase の研究(2) : Aspergillus awamori var.fumeus-1-B42 菌精製 α-D-glucosidase の各種グルコシル基質に対する作用

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Substrate specificity of α-D-glucosidase highly purified from solid-culture extract of Aspergillus awamori var.fumeus-1-B42, and transglucosylation products from maltose by the enzyme, were investigated. The maximal velocities (Vmax) for glucobioses were arranged in the following order, maltose(α-1,4)>nigerose(α-1,6)>kojibiose(α-1,2), and the ratio between these sugars was 1.00 : 0.64 : 0.38 : 0.18. In spite of α-D glucosidase, the enzyme did not hydrolyze α,α-trehalose(α,α-1,1), but hydrolyzed β,β-trehalose(β,β-1,1). Michaelis constants (Km) for glucobioses were as follows: isomaltose(5.78mM)<maltose(6.90mM)<kojibiose(7.14mM)<nigerose(20.8mM)<β,β-trehalose(38.5mM). Vmax values for maltooligosaccharides were arranged in the following order, maltose>maltoriose>maltotetraose>maltopentaose>maltohexaose, and the ratio between these sugars was 1.00 : 0.83 : 0.78 : 0.63 : 0.54. From the fact that the reactivity of the enzyme on the substrated decreased gradually accompanied by increasing degree of polymerization of glucose, it was shown that this enzyme is a type of oligase. Km values for maltooligosaccharides were as follows: maltohexaose(2.47mM)<maltopentaose(2.58mM),maltotetraose(5.62mM)<maltotriose(5.85mM)≦maltose(5.90mM). Vmax values for sugar-alcohol of maltooligosaccharides were the following order, maltotetraitol>maltotritol≫maltitol, and the ratio between these sugar-alcohol was 1.00 : 0.84 : 0.013. Km values for sugar-alcohol of maltooligosaccharides were as follows: maltotetraitol(3.64mM)<maltitol(8.16mM)≦maltotritol(8.33mM). Vmax values for sucrose and p-nitrophenyl-α-D-blucopyranoside were very low as follows: maltose: sucrose: p-nitrophenyl-α-D-blucopyranoside=1.00 : 0.0041 : 0.025. As transglucosylation products from maltose by the enzyme, in a early stage of the reaction panose increased gradually, in a next stage isomaltose and isomaltotriose increased gradually accompanied by the decrease of panose, and in a long time reaction isomaltose and isomaltotriose decreased slowly. The maximum yield of isomaltose from maltose was about 26%, the sum of isomaltose and simaltotriose was about 34%, and the sum of isomaltose, isomaltotriose and panose came up to about 56%.
実践女子大学の論文
2001-04-12

Aspergillus awamori の α-D-glucosidase の研究(2) : Aspergillus awamori var.fumeus-1-B42 菌精製 α-D-glucosidase の各種グルコシル基質に対する作用

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