title: 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.
abstract: 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: D055598:Chemical Phenomena; D002621:Chemistry; D003080:Cold Temperature; D003300:Copper; D004578:Electron Spin Resonance Spectroscopy; D003576:Electron Transport Complex IV; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010100:Oxygen; D013053:Spectrophotometry
chemical_list: D003300:Copper; D003576:Electron Transport Complex IV; D010100:Oxygen