Kinetic evidence for the re‐definition of electron transfer pathways from cytochrome c to O2 within cytochrome oxidase

FEBS Letters

Greenwood, Colin¹  Hill, Bruce C.¹ 

[1] School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, England

关键词: Cytochrome c oxidase;    O2 reduction;    Electron transfer;    Flow-flash photolysis spectrophotometry;    Cytochrome c;    Ionic strength effect;    TMPD;    N;    N;    N′;    N′-tetramethyl-p-phenylenediamine;    EPR;    electron paramagnetic resonance;   

DOI  :  10.1016/0014-5793(84)80113-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The reaction with O₂ of equimolar mixtures of cytochrome c and cytochrome c oxidase in high and low ionic strength buffers has been examined by flow-flash spectrophotometry at room temperature. In low ionic strength media where cytochrome c and the oxidase are bound in an electrostatic, 1:1 complex some of the cytochrome c is oxidised at a faster rate than a metal centre of the oxidase. In contrast, when cytochrome c and cytochrome c oxidase are predominantly dissociated at high ionic strength cytochrome c oxidation occurs only slowly (t =5 s) following the complete oxidation of the oxidase. These results demonstrate that maximal rates of electron transfer from cytochrome c to O₂ occur when both substrates are present on the enzyme. The heterogeneous oxidation of cytochrome c observed in the complex implies more than one route for electron transfer within the enzyme. Possibilities for new electron transfer pathways from cytochrome c to O₂ are proposed.

【 授权许可】

Unknown