title: Cytochrome c peroxidase activity of bovine heart cytochrome oxidase incorporated in liposomes and generation of membrane potential.
abstract: Cytochrome oxidase vesicles catalyzed the peroxidatic oxidation of ferrocytochrome c. The maximal peroxidase activity in the absence of an uncoupling agent was 9.8 mol ferrocytochrome c oxidized/(s X mol heme a), indicating a 5-fold activation compared with the soluble enzyme system. The peroxidase activity was further enhanced 1.2 to 2.1 times upon addition of an uncoupler, carbonyl cyanide p-trifluoromethoxyphenyl hydrazone. The stoichiometry of the reduction of hydrogen peroxide by ferrocytochrome c was established to be 1 : 2, indicating water formation. Potassium cyanide (0.14 mM) completely inhibited the peroxidase activity. The inhibition by 1 mM CO was 40-77% depending on the energized state of cytochrome oxidase vesicles, but in contrast, 85% inhibition was observed with the soluble enzyme. In the energized state the enzyme showed a slightly lower affinity for CO than in the deenergized state. Coupled with the peroxidase activity, a membrane potential of 72 mV was registered transiently; this may be physiologically significant in relation to the energy transduction mechanism.
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000494:pharmacology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002417:Cattle; D003574:Cytochrome c Group / Q000378:metabolism; D003578:Cytochrome-c Peroxidase / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism*; D008564:Membrane Potentials; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D011190:Potassium Cyanide / Q000494:pharmacology
chemical_list: D003574:Cytochrome c Group; D008081:Liposomes; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D002248:Carbon Monoxide; D006861:Hydrogen Peroxide; D010544:Peroxidases; D003578:Cytochrome-c Peroxidase; D003576:Electron Transport Complex IV; D011190:Potassium Cyanide