title: Effect of the nonionic detergent Triton X-100 on mitochondrial succinate-oxidizing enzymes.
abstract: Specific activities of succinate:coenzyme Q reductase, ubiquinone:cytochrome c reductase, cytochrome oxidase, succinate:cytochrome c reductase, succinate oxidase, and ubiquinol oxidase have been measured in rat liver mitochondria in the presence of Triton X-100. The last three activities are much more sensitive to Triton X-100 than the first ones; the data suggest that the electron transport chain components cannot react with each other in the presence of the detergent. At least in the case of succinate:cytochrome c reductase, reconstitution of the detergent-treated membranes with externally added phospholipids reverses the inhibition produced by Triton X-100. These results support the idea that the respiratory chain components diffuse at random in the plane of the inner mitochondrial membrane; the main effect of the detergent would be to impair lateral diffusion by decreasing the area of lipid bilayer. When detergent-treated mitochondrial suspensions are centrifuged in order to separate the solubilized from the particulate material, only the first three enzyme activities mentioned above are found in the supernatants. After centrifugation, a latent ubiquinol:cytochrome c oxidase activity becomes apparent, whereas the same centrifugation process produces inhibition of cytochrome c oxidase in the presence of certain Triton X-100 concentrations. These effects could be due either to a selective solubilization of regulatory or catalytic subunits or to a conformational change of the enzyme-detergent complex.
mesh_terms: D000818:Animals; D042963:Electron Transport Complex II; D066298:In Vitro Techniques; D008930:Mitochondria, Liver / Q000201:enzymology*; D009097:Multienzyme Complexes / Q000378:metabolism; D017830:Octoxynol; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology*; D051381:Rats; D013384:Succinate Cytochrome c Oxidoreductase / Q000378:metabolism; D013385:Succinate Dehydrogenase / Q000378:metabolism; D013386:Succinates / Q000378:metabolism*
chemical_list: D009097:Multienzyme Complexes; D013386:Succinates; D011092:Polyethylene Glycols; D017830:Octoxynol; D010088:Oxidoreductases; D013384:Succinate Cytochrome c Oxidoreductase; C022691:succinate oxidase; D042963:Electron Transport Complex II; D013385:Succinate Dehydrogenase