The oxygen reactive species of cytochrome‐c‐oxidase: An alternate view

FEBS Letters

Sarti, Paolo¹  Wilson, Michael T.¹  Antonini, Giovanni¹  Malatesta, Francesco¹  Brunori, Maurizio¹ 

[1] Department of Biochemical Sciences and CNR Centre for Molecular Biology, University of Rome ‘La Sapienza’ and Department of Experimental Medicine and Biochemical Sciences, University of Rome ‘Tor Vergata’ Rome, Italy

关键词: Cytochrome oxidase;    Electron transfer;    Mitochondria;    Kinetics;    TMPD;    N;    N;    N′;    N′;    -tetramethyl para-phenylenediamine;    cT;    electron transfer;    SVD;    singular value decomposition;    RCR;    respiratory control ratio;   

DOI  :  10.1016/0014-5793(92)80972-J

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

In a recent review article Babcok and Wikström (Nature, 1992, 356, 301–309) proposed that the species of cytochrome-c-oxidase which binds molecular oxygen during turnover is the so-called mixed valence enzyme, in which the binuclear center cytochrome a ₃-Cu _B is reduced, while the cytochrome a/Cu _A sites are oxidized. This proposal is based on earlier work (Morgan and Wikström, Biochemistry 1991, 30, 948–958) in which it was found that the steady-state reduction levels of cytochrome c and cytochrome a in respiring rat liver mitochondria (sustained by ascorbate and TMPD) are quite different, the latter being much more oxidized than the former; evaluation of the steady-state reduction levels demanded a large correction due to the optical contribution of oxidized TMPD⁺ which overlaps with the cytochromes. We report below that application of transient spectroscopy and SVD analysis to respiring rat heart myocytes, under conditions in which the contribution of TMPD⁺ is very small or absent, allows to show that the steady-state reduction levels of cytochrome c and cytochrome a are comparable at all times accessible to measurement in the rapid-scanning stopped-flow spectrophotometer. Our conclusion, in agreement with previous results, is that mixed valence cytochrome-c-oxidase as defined above is not the prevailing oxygen binding species of cytochrome-c-oxidase, unless electron donation to cytochrome c becomes rate limiting.

【 授权许可】

Unknown