Coenzyme Q: Reversal of Inhibition of Succinate Cytochromec Reductase by Lipophilic Compounds

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Science  15 May 1964:
Vol. 144, Issue 3620, pp. 852-853
DOI: 10.1126/science.144.3620.852


The activity of a particulate succinate cytochrome c reductase is inhibited by antimycin, 2-heptyl-4-hydroxyquinoline-N-oxide, 2-(9-cyclohexyl-n-nonyl)-3-hydroxy-1,4naphthoquinone and thenoyltrifluoroacetone. The ratio of antimycin A (required for complete inhibition) to the molar content of the cytochrome b of the reductase is approximately 0.5 in contrast to the reported value of 1.0 or higher for succinate oxidase preparations. However, the degreeof inhibition by antimycin is dependent on the exogenous coenzyme Q (ubiquinone) present. Indeed, the inhibition from any of these compounds is competitively reversed by exogenous coenzyme Q in the system.