The Rhizopus niveus glucoamylase-catalyzed reaction for substrate maltose in the absence or presence of acetonitrile

In the presence or absence of acetonitrile CH3CN, the molecular mechanism on the Rhizopus niveus glucoamylse (GA)-catalyzed reaction was studied by the steady-state kinetics for a substrate maltose (G2). At high concentration of G2, the GA-catalyzed reaction was observed not to obey the Michaelis kinetics and was reasonably explained with a mechanism of the substrate-inhibition involving the ternary complex ESS. Moreover, CH3CN was found to effect on (decrease in) the dissociation constants Ks (for ES) and Ks' (for ESS). No transglucosylation was confirmed for the G2 reaction. These findings will support the hydrophobic-driven mechanism proposed in a previous study.