Intermediates Formed in the Reaction of Cytochrome c Oxidase with Oxygen

Cytochrome c oxidase is the terminal enzyme in the electron transport chain. In this role, it catalyzes the transfer of four electrons from cytochrome c to di-oxygen, the physiological substrate. Oxygen binds to cytochrome c oxidase on the microsecond time scale and is fully reduced to water in milliseconds. An understanding of the molecular basis for the catalytic mechanism of the oxygen reduction has been sought after for many years but has remained elusive due to the difficulty in establishing the identity of each intermediate on this time scale by optical spectroscopic techniques. Recently, we [1–5] and others [6–11] have applied resonance Raman spectroscopy to the study of the oxygen reduction process and achieved considerable success. In this paper, we discuss the findings from the resonance Raman scattering experiments and based on these results present a model for the catalytic pathway.