IUBMB Enzyme Nomenclature


Accepted name: menaquinol oxidase (H+-transporting)

Reaction: 2 menaquinol + O2 + n H+[side 1] = 2 menaquinone + 2 H2O + n H+[side 2]

Other name(s): cytochrome aa3-600 oxidase; cytochrome bd oxidase; menaquinol:O2 oxidoreductase (H+-transporting)

Systematic name: menaquinol:oxygen oxidoreductase (H+-transporting)

Comments: Cytochrome aa3-600, one of the principal respiratory oxidases from Bacillus subtilis, is a member of the heme-copper superfamily of oxygen reductases, and is a close homologue of the cytochrome bo3 ubiquinol oxidase from Escherichia coli, but uses menaquinol instead of ubiquinol as a substrate.The enzyme also pumps protons across the membrane bilayer, generating a proton motive force.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Lauraeus, M. and Wikstrom, M. The terminal quinol oxidases of Bacillus subtilis have different energy conservation properties. J. Biol. Chem. 268 (1993) 11470-11473. [PMID: 8388393]

2. Lemma, E., Simon, J., Schagger, H. and Kroger, A. Properties of the menaquinol oxidase (Qox) and of qox deletion mutants of Bacillus subtilis. Arch. Microbiol. 163 (1995) 432-438. [PMID: 7575098]

3. Yi, S.M., Narasimhulu, K.V., Samoilova, R.I., Gennis, R.B. and Dikanov, S.A. Characterization of the semiquinone radical stabilized by the cytochrome aa3-600 menaquinol oxidase of Bacillus subtilis. J. Biol. Chem. 285 (2010) 18241-18251. [PMID: 20351111]

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

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