Cytochrome OxidaseBased in part on the article Cytochrome Oxidase by Gerald T. Babcock which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Abstract

Heme‐copper oxidase is the current generic name for the superfamily of respiratory enzymes that are responsible for cell respiration in the mitochondria of eukaryotic cells as well as in aerobic prokaryotes, and which shows substantial structural and functional homology among its members. This group of enzymes is responsible for more than 90% of the consumption of dioxygen by living organisms on this planet. Harnessing the high oxidizing power of the O 2 /H 2 O redox couple some 2.5–3 billion years ago made a revolutionary impact on evolution. The oxidation of foodstuffs by O 2 gave an approx. 15‐fold energetic advantage over previously predominant glycolytic oxidations, and was the prerequisite for the development and evolution of all higher multicellular organisms. Apart from mastering the O 2 reduction chemistry in a safe and economical fashion, these enzymes also function as remarkable energy transducers that convert much of the free energy released in the process into a proton gradient, which is subsequently used to drive virtually all energy‐requiring processes in the cell. This article reviews the major advances in the last 10 years of research on this group of enzymes. The major highlights are the elucidation of the crystal structures of several oxidases, major advances in the understanding of the mechanism of O 2 activation and reduction at the bimetallic heme iron‐copper active site, and recent progress in the ongoing research on the perhaps most intriguing but least known function, redox‐coupled proton translocation.