Catalytic Reduction of O2 by Cytochrome c Using a Synthetic Model of Cytochrome c Oxidase

Abstract

Cytochrome c oxidase (CcO) catalyzes the four-electron reduction of oxygen to water, the one-electron reductant Cytochrome c (Cytc) being the source of electrons. Recently we reported a functional model of CcO that electrochemically catalyzes the four-electron reduction of O₂ to H₂O (Collman et al. Science2007, 315, 1565). The current paper shows that the same functional CcO model catalyzes the four-electron reduction of O₂ using the actual biological reductant Cytc in a homogeneous solution. Both single and steady-state turnover kinetics studies indicate that O₂ binding is rate-determining and that O−O bond cleavage and electron transfer from reduced Cytc to the oxidized model complex are relatively fast.