The transient-state kinetics of L-glutamate dehydrogenase. pH-dependence of the burst rate parameters.
The pH dependence of the initial transient velocity of NADPH production during the burst phase of the oxidative deamination of L-glutamate by L-glutamate dehydrogenase (L-glutamate : NAD(P)+ oxidoreductase (deaminating), EC 1.4.1.3) and NADP+ has been measured by stopped-flow spectrophotometry. These studies provide evidence that the entire pH dependence below pH 8.26 arises from reaction steps contributing to V of the burst with an apparent pKa of 8.1 +/- 0.1. The data are consistent with a model in which the formation of the first enzyme-coenzyme-substrate ternary complex on the reaction path equilibrates rapidly and in which the pH-dependent steps are mechanistically close to and may include the catalytic hydrogen transfer itself. At pH 8.87, there is evidence that L-glutamate binds less tightly to the enzyme and to the enzyme-NADP+ complex than at lower pH values.
D000818:Animals; D002417:Cattle; D005969:Glutamate Dehydrogenase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008433:Mathematics; D009243:NAD; D009249:NADP; D013997:Time Factors
D009243:NAD; D009249:NADP; D005969:Glutamate Dehydrogenase