Cytochrome c oxidase: Intermediates of the catalytic cycle and their energy-coupled interconversion

► Nomenclature of cytochrome c oxidase intermediates needs to be revised. ► Cytochrome oxidase intermediates are homologous to compounds of P450 and peroxidases. ► The primary role of the K-channel is to enable smooth heterolytic O-O bond scission. ► H+-pumping mechanisms may differ for different steps in the catalytic cycle.