pH changes associated with cytochrome c oxidase reaction with H2O2 Protonation state of the peroxy and oxoferryl intermediates

FEBS Letters

Capitanio, N.²  Papa, S.²  Vygodina, T.V.¹  Konstantinov, A.A.¹ 

[1] A.N. Belozersky Institute of Physico-Chemical Biology, Moscow, State Unversity, Moscow, Russia;Institute of Biochemistry and Medical Chemistry, University of Bari, Italy

关键词: Cytochrome oxidase;    Proton pump;    Oxygen intermediate;    Hydrogen peroxide;    Reaction mechanism;    Superoxide generation;    COX;    cytochrome oxidase;    Co(phen);    tris-phenanthroline complex of CoIII;    FeCy;    ferricyanide;    Ox;    P and F;    the oxidized;    peroxy and oxoferryl states of cytochrome oxidase;    SOD;    superoxide dismutase;   

DOI  :  10.1016/0014-5793(92)81412-F

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

pH changes associated with the mitochondrial cytochrome oxidase reaction with H₂O₂ have been studied. In the presence of forricyanide or Tris-phenanthroline complex of Co^III 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:

【 授权许可】

Unknown