Steady-state Inhibitory Kinetic Studies on Almond β-Glucosidase-catalyzed Reaction : Binding Sites of Monosaccharides(Biological Chemistry)

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Steady-state inhibitory kinetic studies on almond β-glucosidase-catalyzed reactions were done to elucidate the binding subsite of several monosaccharides on this enzyme. Glucono-1,5-lactone (a transition-state analog), glucose, 2-deoxy glucose, fucose, and methyl α-glucoside showed mixed-type inhibition, but galactose, galactosamine, mannose, N-acetyl glucosamine, and glucosamine showed pure competitive inhibition on the hydrolysis of p-nitrophenyl β-glucoside. These results are reasonably accounted for by assuming that the former monosaccharides (the mixed type inhibitors) bind to subsite 1 (the nonreducing-end side subsite to which the nonreducing-end glucose residue of a substrate binds in a productive binding mode), and that the latter (the competitive inhibitors) bind to subsite 2, the adjacent subsite to subsite 1. The binding affinity (-ΔG°) of glucono-l,5-lactone (-ΔG°=6.7 kcal mol^<-1> at pH 5.0, 25℃) was significantly greater than those of the others (0.3〜1.6 kcal mol^<-1>).
社団法人日本農芸化学会の論文
1989-05-23