Resonance Raman Study on Catalytic Intermediates of Cytochrome c Oxidase

Resonance Raman (RR) spectra of redox- and reaction-intermediates of cytochrome c oxidase was investigated. Aerobic laser irradiation to this enzyme produced a photo-steady state Eor catalytic reduction of oxygen and Raman scattering from it probed the RR spectra of cytochrome a 2+ and cytochrome a 3 3+ separately upon excitations at 441.6 and 406.7 nm, respectively. Measurements with variable-speed spinning cell allowed to deduce the rate constant of electron tansfer from cytochrome a 2+ to cytochrome a 3 3+ to be 0.5 s -1 at most. A mixed flow transient Raman apparatus was constructed and the RR spectrum of an oxygenated intermediate having the Fe 2+ heme in cytochrome a and the Fe 2+ -O 2 or Fe 2+ =O heme in cytochrome a 3 was observed.