pH changes associated with cytochrome c oxidase reaction with H2O2 Protonation state of the peroxy and oxoferryl intermediates
Open Access
- 2 November 1992
- journal article
- Published by Wiley in FEBS Letters
- Vol. 312 (1) , 71-74
- https://doi.org/10.1016/0014-5793(92)81412-f
Abstract
PH changes associated with the mitochondrial cytochrome oxidase reaction with H2O2 have been studied. In the presence of forricyanide or Tris‐phenanthroline complex of CoIII as electron acceptors, reaction or H2O2 with the oxidized cytochrome oxidase is accompanied by a steady proton release with a rate constant of ca. 3 M−1 s−1 at pH 6.8. The acidification is completely inhibited by superoxide dismutase and its pro‐steady‐state kinetics correlates with that of the oxoferryl compound (F) accumulation. Apparently, the proton release is linked to superoxide generation by cytochrome oxidase under these conditions. In the presence of superoxide dismutase and without the electron acceptors, the H2O2‐induced transitions of cytochrome oxidase from the oxidized to the peroxy (P) and from the peroxy to the oxoferryl state are not associated with any significant proton release or uptake. The results point to the following mechanism of O− 2 generation and protonation states of the cytochrome oxidase compounds P and F:Keywords
This publication has 20 references indexed in Scilit:
- Oxygen activation and the conservation of energy in cell respirationNature, 1992
- Uptake and release of protons during the reaction between cytochrome c oxidase and molecular oxygen: a flow-flash investigationBiochemistry, 1991
- Cytochrome oxidase: Some unsolved problems and controversial issuesArchives of Biochemistry and Biophysics, 1990
- Identification of the electron transfers in cytochrome oxidase that are coupled to proton-pumpingNature, 1989
- Effect of pH on the spectrum of cytochrome c oxidase hydrogen peroxide complexBiochimica et Biophysica Acta (BBA) - Bioenergetics, 1989
- Possible Protonmotive Osmochemistry in Cytochrome OxidaseAnnals of the New York Academy of Sciences, 1988
- A new redox loop formality involving metal‐catalysed hydroxide‐ion translocation A hypothetical Cu loop mechanism for cytochrome oxidaseFEBS Letters, 1987
- Evidence for two H2O2‐binding sites in ferric cytochrome c oxidase Indication to the O‐cycle?FEBS Letters, 1987
- Chemiosmotic coupling in cytochrome oxidaseFEBS Letters, 1985
- Redox bohr‐effects in the cytochrome system of mitochondriaFEBS Letters, 1979