The Enzyme Database

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Accepted name: cytochrome-c oxidase
Reaction: 4 ferrocytochrome c + O2 + 8 H+[side 1] = 4 ferricytochrome c + 2 H2O + 4 H+[side 2]
For diagram, click here
Other name(s): cytochrome aa3; cytochrome caa3; cytochrome bb3; cytochrome cbb3; cytochrome ba3; cytochrome a3; Warburg's respiratory enzyme; indophenol oxidase; indophenolase; complex IV (mitochondrial electron transport); ferrocytochrome c oxidase; cytochrome oxidase (ambiguous); NADH cytochrome c oxidase (incorrect)
Systematic name: ferrocytochrome-c:oxygen oxidoreductase
Comments: An oligomeric membrane heme-Cu:O2 reductase-type enzyme that terminates the respiratory chains of aerobic and facultative aerobic organisms. The reduction of O2 to water is accompanied by the extrusion of four protons. The cytochrome-aa3 enzymes of mitochondria and many bacterial species are the most abundant group, but other variations, such as the bacterial cytochrome-cbb3 enzymes, also exist. All of the variants have a conserved catalytic core subunit (subunit I) that contains a low-spin heme (of a- or b-type), a binuclear metal centre composed of a high-spin heme iron (of a-, o-, or b-type heme, referred to as a3, o3 or b3 heme), and a Cu atom (CuB). Besides subunit I, the enzyme usually has at least two other core subunits: subunit II is the primary electron acceptor; subunit III usually does not contain any cofactors, but in the case of cbb3-type enzymes it is a diheme c-type cytochrome. While most bacterial enzymes consist of only 3–4 subunits, the mitochondrial enzyme is much more complex and contains 14 subunits.
Links to other databases: BRENDA, EXPASY, Gene, GTD, KEGG, MetaCyc, PDB, CAS registry number: 9001-16-5
1.  Keilin, D. and Hartree, E.F. Cytochrome oxidase. Proc. R. Soc. Lond. B Biol. Sci. 125 (1938) 171–186.
2.  Keilin, D. and Hartree, E.F. Cytochrome and cytochrome oxidase. Proc. R. Soc. Lond. B Biol. Sci. 127 (1939) 167–191.
3.  Wainio, W.W., Eichel, B. and Gould, A. Ion and pH optimum for the oxidation of ferrocytochrome c by cytochrome c oxidase in air. J. Biol. Chem. 235 (1960) 1521–1525.
4.  Yonetani, T. Studies on cytochrome oxidase. II. Steady state properties. J. Biol. Chem. 235 (1960) 3138–3243. [PMID: 13787372]
5.  Yonetani, T. Studies on cytochrome oxidase. III. Improved purification and some properties. J. Biol. Chem. 236 (1961) 1680–1688. [PMID: 13787373]
6.  Henning, W., Vo, L., Albanese, J. and Hill, B.C. High-yield purification of cytochrome aa3 and cytochrome caa3 oxidases from Bacillus subtilis plasma membranes. Biochem. J. 309 (1995) 279–283. [DOI] [PMID: 7619069]
7.  Keightley, J.A., Zimmermann, B.H., Mather, M.W., Springer, P., Pastuszyn, A., Lawrence, D.M. and Fee, J.A. Molecular genetic and protein chemical characterization of the cytochrome ba3 from Thermus thermophilus HB8. J. Biol. Chem. 270 (1995) 20345–20358. [DOI] [PMID: 7657607]
8.  Ducluzeau, A.L., Ouchane, S. and Nitschke, W. The cbb3 oxidases are an ancient innovation of the domain bacteria. Mol. Biol. Evol. 25 (2008) 1158–1166. [DOI] [PMID: 18353797]
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