Characterization of the intermediates in the reaction of mixed-valence state soluble cytochrome oxidase with oxygen at low temperatures by optical and electron-paramagnetic-resonance spectroscopy

Biochem J. 1980 Jan 1;185(1):155-67. doi: 10.1042/bj1850155.


The reaction of soluble mixed-valence-state (a3+CuA 2+.CuB + A32+) cytochrome oxidase with O2 at low temperature was studied by optical and e.p.r. spectroscopy. The existence of three intermediates [Clore & Chance (1978) Biochem. J. 173, 799-8101] was confirmed. From the e.p.r data it is clear that cytochrome a and CuA remain in the low-spin ferric and cupric states respectively throughout the reaction. No e.p.r. signals attributable to cytochrome a3 or CuB were seen in the intermediates. The difference spectra (intermediates minus unliganded mixed-valence-state cytochrome oxidase) and absolute spectra of the three intermediates were obtained. The chemcal nature of the three intermediates is discussed in terms of their spectroscopic properties. A catalytic cycle for cytochrome oxidase is proposed.

MeSH terms

  • Chemical Phenomena
  • Chemistry
  • Cold Temperature
  • Copper
  • Electron Spin Resonance Spectroscopy
  • Electron Transport Complex IV*
  • Models, Chemical
  • Oxidation-Reduction
  • Oxygen*
  • Spectrophotometry


  • Copper
  • Electron Transport Complex IV
  • Oxygen