Two‐electron reduction is required for rapid internal electron transfer in resting, pulsed and oxygenated cytochrome c oxidase

FEBS Letters

Brzezinski, Peter¹  Thörnström, Per-Eric¹  Fabian, Marian¹  Malmström, Bo G.¹ 

[1] Department of Biochemistry and Biophysics, University of Göteborg and Chalmers University of Technology, S-412 96 Göteborg, Sweden

关键词: Cytochrome oxidase;    Cytochrome c;    Cytochrome a;    Transient kinetics;    Redox-linked conformation;    Electron gating;   

DOI  :  10.1016/0014-5793(87)81529-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The resting as well as the 420 nm and 428 nm forms of cytochrome oxidase have been studied in kinetic experiments with an excess of enzyme over reduced cytochrome c. No difference was found in the behavior of the two activated forms. With all three forms, a fraction of cytochrome a was reoxidized with a rate which was much lower than k _cat. This suggests that intramolecular transfer to the dioxygen-reducing site occurs only if both cytochrome a and Cu_A are reduced. An initial rapid phase in the oxidation of cytochrome a in the pulsed and oxygenated enzymes is related to the presence of a three-electron-reduced dioxygen intermediate. The increased catalytic activity of pulsed and oxygenated oxidase can be explained on the basis of a shift in the redox equilibrium between cytochrome a and Cu_A.

【 授权许可】

Unknown