EC - Ubiquinol oxidase (H+-transporting)

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IntEnz Enzyme Nomenclature


Accepted name:
ubiquinol oxidase (H+-transporting)
Other names:
cytochrome bb3 oxidase
cytochrome bo oxidase
cytochrome bo3 oxidase
Systematic name:
ubiquinol:oxygen oxidoreductase (H+-transporting)




Contains a dinuclear centre comprising two hemes, or heme and copper. This terminal oxidase enzyme generates proton motive force by two mechanisms: (1) transmembrane charge separation resulting from utilizing protons and electrons originating from opposite sides of the membrane to generate water, and (2) active pumping of protons across the membrane. The bioenergetic efficiency (the number of charges driven across the membrane per electron used to reduce oxygen to water) depends on the enzyme; for example, for the bo3 oxidase it is 2, while for the bd-II oxidase it is 1. cf. EC, ubiquinol oxidase ubiquinol oxidase (electrogenic, proton-motive force generating).

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0009486
UniProtKB/Swiss-Prot: (10) [show] [UniProt]


  1. Abramson, J., Riistama, S., Larsson, G., Jasaitis, A., Svensson-Ek, M., Laakkonen, L., Puustinen, A., Iwata, S., Wikstrom, M.
    The structure of the ubiquinol oxidase from Escherichia coli and its ubiquinone binding site.
    Nat. Struct. Biol. 7 : 910-917 (2000). [PMID: 11017202]
  2. Yap, L. L., Lin, M. T., Ouyang, H., Samoilova, R. I., Dikanov, S. A., Gennis, R. B.
    The quinone-binding sites of the cytochrome bo3 ubiquinol oxidase from Escherichia coli.
    Biochim. Biophys. Acta 1797 : 1924-1932 (2010). [PMID: 20416270]
  3. Stenberg, F., von Heijne, G., Daley, D. O.
    Assembly of the cytochrome bo3 complex.
    J. Mol. Biol. 371 : 765-773 (2007). [PMID: 17583738]
  4. Choi, S. K., Lin, M. T., Ouyang, H., Gennis, R. B.
    Searching for the low affinity ubiquinone binding site in cytochrome bo3 from Escherichia coli.
    Biochim Biophys Acta Bioenerg 1858 : 366-370 (2017). [PMID: 28235459]
  5. Choi, S. K., Schurig-Briccio, L., Ding, Z., Hong, S., Sun, C., Gennis, R. B.
    Location of the Substrate Binding Site of the Cytochrome bo3 Ubiquinol Oxidase from Escherichia coli.
    J. Am. Chem. Soc. 139 : 8346-8354 (2017). [PMID: 28538096]

[EC created 2011 as EC, modified 2014, transferred 2018 to EC]