Facilitated intramolecular electron transfer in cytochrome bo-type ubiquinol oxidase initiated upon reaction of the fully reduced enzyme with dioxygen. 1994

Y Orii, and T Mogi, and M Kawasaki, and Y Anraku
Department of Public Health, Faculty of Medicine, Kyoto University, Japan.

Flow-flash and double-flash studies of the reaction of fully reduced bo-type quinol oxidase with oxygen have revealed that a single turnover of the enzyme proceeds much faster than mammalian cytochrome c oxidase. Facilitated intramolecular electron transfer in the bo-type oxidase with k > 5 x 10(4) s-1 at pH 7.4 and 20 degrees C is responsible for this fast turnover. The kinetics of this reaction indicates that the oxygen reduction does not require electron exchange between quinol oxidase molecules, each having three metal centers. Thus, a bound quinol in the fully reduced enzyme is suggested to be an electron source for complete reduction of dioxygen into water supplementing electrons provided by the metal centers. A single turnover of the quinol oxidase yields a novel spectral species with a Soret maximum at 415 nm corresponding to a 'pulsed' state of mammalian cytochrome c oxidase.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D010084 Oxidation-Reduction A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471). Redox,Oxidation Reduction
D010100 Oxygen An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration. Dioxygen,Oxygen-16,Oxygen 16
D003576 Electron Transport Complex IV A multisubunit enzyme complex containing CYTOCHROME A GROUP; CYTOCHROME A3; two copper atoms; and 13 different protein subunits. It is the terminal oxidase complex of the RESPIRATORY CHAIN and collects electrons that are transferred from the reduced CYTOCHROME C GROUP and donates them to molecular OXYGEN, which is then reduced to water. The redox reaction is simultaneously coupled to the transport of PROTONS across the inner mitochondrial membrane. Cytochrome Oxidase,Cytochrome aa3,Cytochrome-c Oxidase,Cytochrome Oxidase Subunit III,Cytochrome a,a3,Cytochrome c Oxidase Subunit VIa,Cytochrome-c Oxidase (Complex IV),Cytochrome-c Oxidase Subunit III,Cytochrome-c Oxidase Subunit IV,Ferrocytochrome c Oxygen Oxidoreductase,Heme aa3 Cytochrome Oxidase,Pre-CTOX p25,Signal Peptide p25-Subunit IV Cytochrome Oxidase,Subunit III, Cytochrome Oxidase,p25 Presequence Peptide-Cytochrome Oxidase,Cytochrome c Oxidase,Cytochrome c Oxidase Subunit III,Cytochrome c Oxidase Subunit IV,Oxidase, Cytochrome,Oxidase, Cytochrome-c,Signal Peptide p25 Subunit IV Cytochrome Oxidase,p25 Presequence Peptide Cytochrome Oxidase
D004579 Electron Transport The process by which ELECTRONS are transported from a reduced substrate to molecular OXYGEN. (From Bennington, Saunders Dictionary and Encyclopedia of Laboratory Medicine and Technology, 1984, p270) Respiratory Chain,Chain, Respiratory,Chains, Respiratory,Respiratory Chains,Transport, Electron
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D013053 Spectrophotometry The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.

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