Effect of cryosolvent on transient kinetics of the glutamate dehydrogenase reaction

The transient and steady-state kinetics of the oxidative deamination of L-glutamate by glutamate dehydrogenase and NADP in both aqueous solution and 30% methanol are compared. Methanol causes an approximately 5-fold tightening of the enzyme--L-glutamate binary complex and an approximately 2-fold reduction of the interaction parameter for the ternary enzyme--NADP--L-glutamate complex. The most dramatic effect of methanol on the time course of the reaction is what appears to be a conversion of the enzyme at substoichiometric initial levels of reactant NADP to a form from which product alpha-ketoglutarate does not readily dissociate. This conversion appears only at NADP concentrations over one-third of the enzyme active site concentration.