Mechanistic study on the inactivation of general acyl-CoA dehydrogenase by a metabolite of hypoglycin A

General acyl-CoA dehydrogenase (GAD) is a flavin-dependent (FAD) enzyme that catalyzes the oxidation of a fatty acyl-CoA to the corresponding alpha , beta -enolyl-CoA. When GAD is exposed to (methylenecyclopropyl)-acetyl-CoA (MCPA-CoA) a metabolite of hypoglycin A that is the causative agent of Jamaican vomiting sickness, time-dependent inhibition occurs with concomitant bleaching of the active-site FAD. The inactivation mechanism is generally believed to be initiated by C sub( alpha ) anion formation followed by ring fragmentation and the covalent modification of FAD. However, formation of a cyclopropyl radical intermediate through one-electron oxidation followed by ring opening and then radical recombination to yield a modified FAD is an appealing alternative. The mechanistic insights deduced from this study support our early notion that inactivation of GAD by MCPA-CoA is likely to proceed through a radical mechanism.