Zinc ions inhibit oxidation of cytochrome c oxidase by oxygen

FEBS Letters

Brzezinski, Peter¹  Aagaard, Anna¹ 

[1] Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden

关键词: Electron transfer;    Flow-flash;    Proton pumping;    Cytochrome aa 3;    Flash photolysis;    Rhodobacter sphaeroides;    CuA;    copper A;    CuB;    copper B;    binuclear centre;    CuB and haem a 3;    O;    fully oxidised enzyme;    Pr;    peroxy intermediate (formed upon reaction of the fully reduced enzyme with O2);    F;    oxo-ferryl intermediate;    E(I-286);    glutamic acid of subunit I at position 286;   

DOI  :  10.1016/S0014-5793(01)02299-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Cytochrome c oxidase is a membrane-bound enzyme that catalyses the reduction of O₂ to H₂O and uses part of the energy released in this reaction to pump protons across the membrane. We have investigated the effect of addition of Zn²⁺ on the kinetics of two reaction steps in cytochrome c oxidase that are associated with proton pumping; the peroxy to oxo-ferryl (P_r→F) and the oxo-ferryl to oxidised (F→O) transitions. The Zn²⁺ binding resulted in a decrease of the F→O rate from 820 s⁻¹ (no Zn²⁺) to a saturating value of ∼360 s⁻¹ with an apparent K _D of ∼2.6 μM. The P_r→F rate (∼10⁴ s⁻¹ before addition of Zn²⁺) decreased more slowly with increasing Zn²⁺ concentration and a K _D of ∼120 μM was observed. The effects on both kinetic phases were fully reversible upon addition of EDTA. Since both the P_r→F and F→O transitions are associated with proton uptake through the D-pathway, a Zn²⁺-binding site is likely to be located at the entry point of this pathway, where several carboxylates and histidine residues are found that may co-ordinate Zn²⁺.

【 授权许可】

Unknown