Essentiality of coenzyme Q for the oxidation of -glycerophosphate by pig brain mitochondria

Serial extraction of lyophilized pig brain mitochondria with cold pentane resulted in complete loss of α-glycerophosphate oxidase activity. On titration with coenzyme Q₁₀ the activity was fully recovered. On comparing the decline of α-glycerophosphate, NADH, and succinoxidase activities during serial extraction with pentane, α-glycerophosphate oxidation was always the first to be lost. Extraction of coenzyme Q₁₀ from lyophilized brain mitochondria with pentane does not affect the activities of α-glycerophosphate or NADH dehydrogenase, but succinate dehydrogenase is partially inactivated. Reversible inactivation of the α-glycerophosphate oxidase system on depletion of the coenzyme Q content is taken as evidence that coenzyme Q is an obligatory component of this system. In accord with the conclusion that coenzyme Q is probably the physiological oxidant of α-glycerophosphate dehydrogenase, in antimycin-treated brain mitochondria α-glycerophosphate causes full activation of endogenous succinate dehydrogenase, in analogy to the previously observed activation by NAD-linked substrates in liver and heart mitochondria and by NADH in submitochondrial particles.