Primary Intermediate in the Reaction of Mixed-Valence Cytochrome c Oxidase with Oxygen

Sanghwa Han, Yuan Chin Ching, Denis L. Rousseau

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39 Scopus citations


The reaction of dioxygen with mixed-valence cytochrome c oxidase was followed in a rapid-mixing continuous-flow apparatus. The optical absorption difference spectrum and a kinetic analysis confirm the presence of the primary oxygen intermediate in the 0-100-μs time window. The resonance Raman spectrum of the iron-dioxygen stretching mode (568 cm−1) supplies evidence that the degree of electron transfer from the iron atom to the dioxygen is similar to that in oxy complexes of other heme proteins. Thus, the Fe-O2 bond does not display any unique structural features that could account for the rapid reduction of dioxygen to water. Furthermore, the frequency of the iron-dioxygen stretching mode is the same as that of the primary intermediate in the fully reduced enzyme, indicating that the oxidation state of cytochrome a plays no role in controlling the initial properties of the oxygen binding site.

Original languageEnglish (US)
Pages (from-to)1380-1384
Number of pages5
Issue number6
StatePublished - Feb 1 1990
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry


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