On the mechanism of NADP + -linked isocitrate dehydrogenase from heart mitochondria. I. The kinetics of dissociation of NADPH from its enzyme complex

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Abstract
The kinetics of dissociation of NADPH from its complex with isocitrate dehydrogenase and from the abortive complex of enzyme, Mg2+, isocitrate and NADPH [from ox heart mitochondria] were studied in phosphate and triethanolamine buffers by means of rapid fluorescence measurements. The reactions are complex; probably a conformational equilibrium of each of the complexes is involved, and this conformational change is responsible for a slow approach to the steady-state rate of oxidative decarboxylation observed previously in triethanolamine buffer under certain conditions (Dalziel, et al., 1978). Release of free NADPH product is not the rate-limiting step in oxidative decarboxylation in the steady state. The validity of the ligand displacement method used to measure the dissociation kinetics of the enzyme-NADPH complex was studied by computer simulation.