Steady-State Kinetic and Calorimetric Studies on the Binding of Aspergillus niger Glucoamylase with Gluconolactone, 1-Deoxynojirimycin, and β-Cyclodextrin

概要

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Binding equilibria of Aspergillus niger glucoamylase with its several ligands were observed to analyze the binding modes of the ligands. Steady-state kinetic studies using p-nitrophenyl α-glucoside as a substrate showed that 1-deoxynojirimycin, which is a mixed type inhibitor for Rhizopus glucoamylase, was a competitive type inhibitor bound at the active site of the enzyme, but gluconolactone, which is also a mixed type inhibitor for Rhizopus glucoamylase, was a non-competitive type inhibitor forming a nonproductive ternary complex with the enzyme and the substrate. β-Cyclodextrin, which binds to the starch-binding domain of the enzyme, did not inhibit the enzyme activity, showing that there was no interaction between the catalytic domain and the starch-binding domain for the binding of the substrate and β-cyclodextrin. Isothermal titration calorimetry showed that one 1-deoxynojirimycin molecule and two β-cyclodextrin molecules bind to the catalytic domain and the starch-binding domain of the enzyme, respectively, and there is no significant interaction between the binding of these ligands.
社団法人日本農芸化学会の論文
1996-12-23