The transient-state kinetics of l-glutamate dehydrogenase pH-dependence of the burst rate parameters
1977; Elsevier BV; Volume: 481; Issue: 2 Linguagem: Inglês
10.1016/0005-2744(77)90271-6
ISSN1878-1454
AutoresAlan H. Colen, Ralph R. Wilkinson, Harvey F. Fisher,
Tópico(s)Photoreceptor and optogenetics research
ResumoThe 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.
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