Cytochrome c Oxidase

Abstract

Abstract Cytochrome c oxidase is the key enzyme of cell respiration in all eukaryotes and many prokaryotes. The cytochrome c oxidases belong to the haem–copper superfamily of structurally and functionally related enzymes; though related in structure, some bacterial variants lack amino acid residues that are known to be obligatory for the function of the members of the main family. All haem–copper oxidases have a unique bimetallic active site catalysing reduction of dioxygen (O 2 ) to water and an adjacent second haem group that donates electrons to this site. Here, the mechanism of O 2 reduction is reviewed. The membrane‐bound enzyme couples this reaction to translocation of protons across the membrane, and thus functions as a primary energy transducer that contributes to the formation of ATP (adenosine triphosphate) in aerobic life. The most recent knowledge of the function of this ‘proton pump’ is discussed. It is concluded that cytochrome c oxidase is an electrostatic energy‐transducing machine with high efficiency. Key Concepts: Cytochrome c oxidase is an electrostatically coupled energy transducer. The high affinity for O 2 is due to kinetic ligand trapping. O 2 reduction in cell respiration yields no reactive oxygen species.