Regulation of the redox potential of general acyl-CoA dehydrogenase by substrate binding

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Abstract
Significant thermodynamic changes have been observed for general acyl-CoA dehydrogenase (GAD) upon substrate binding. Spectroelectrochemical studies of GAD and several of its substrate have revealed that these substrates are essentially isopotential for chain lengths of C-4 to C-16 (E.degree.'' = -0.038 to -0.045 V vs SHE). When GAD is bound by these substrates, a dramatic shift in the midpoint potential of the enzyme is observed (E.degree.'' = -0.136 V for ligand-free GAD and -0.026 V for acyl-CoA-bound GAD), thus allowing a thermodynamically favorable transfer of electrons from substrate to enzyme. This contrasts with values reported elsewhere. From these data an isopotential scheme of electron delivery into the electron-transport chain is proposed.