title: Inhibition of the mitochondrial bc1 complex by dibromothymoquinone.
abstract: We have studied the effects of dibromothymoquinone (DBMIB) in various redox activities of the succinate-cytochrome c span of the mitochondrial respiratory chain. At concentrations higher than 50 mol/mol of cytochrome c1 the inhibitor produces a bypass of electron transfer on the substrate side of the bc1 complex, because of its autooxidation capability. This induces an artifactual overestimation of the real inhibition titer of the redox activity of this enzyme, which has been found to be 3-6 mol/mol of cytochrome c1 by following the ubiquinol-cytochrome c reductase activity. This action is reversed by addition of excess of sulphydryl compounds like cysteine.
mesh_terms: D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group / Q000378:metabolism; D003991:Dibromothymoquinone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004579:Electron Transport / Q000187:drug effects; D014450:Electron Transport Complex III; D008929:Mitochondria, Heart / Q000201:enzymology*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects; D011808:Quinone Reductases / Q000037:antagonists & inhibitors*; D011809:Quinones / Q000494:pharmacology*; D013367:Submitochondrial Particles / Q000201:enzymology; D013386:Succinates / Q000378:metabolism; D019802:Succinic Acid
chemical_list: D003574:Cytochrome c Group; D009097:Multienzyme Complexes; D011809:Quinones; D013386:Succinates; D003991:Dibromothymoquinone; D019802:Succinic Acid; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases; D014450:Electron Transport Complex III