IUBMB Enzyme Nomenclature


Accepted name: caldariellaquinol oxidase (H+-transporting)

Reaction: 2 caldariellaquinol + O2 + n H+[side 1] = 2 caldariellaquinone + 2 H2O + n H+[side 2]

Glossary: caldariellaquinol = 6-(3,7,11,15,19,23-hexamethyltetracosyl)-5-(methylsulfanyl)-1-benzothiophene-4,7-diol

Other name(s): SoxABCD quinol oxidase; SoxABCD complex; quinol oxidase SoxABCD; SoxM supercomplex; aa3-type quinol oxidase; aa3 quinol oxidase; cytochrome aa3; terminal quinol oxidase; terminal quinol:oxygen oxidoreductase; caldariella quinol:dioxygen oxidoreductase; cytochrome aa3-type oxidase; caldariellaquinol:O2 oxidoreductase (H+-transporting)

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

Comments: A copper-containing cytochrome. The enzyme from thermophilic archaea is part of the terminal oxidase and catalyses the reduction of O2 to water, accompanied by the extrusion of protons across the cytoplasmic membrane.

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


1. Gleissner, M., Kaiser, U., Antonopoulos, E. and Schafer, G. The archaeal SoxABCD complex is a proton pump in Sulfolobus acidocaldarius. J. Biol. Chem. 272 (1997) 8417-8426. [PMID: 9079667]

2. Purschke, W.G., Schmidt, C.L., Petersen, A. and Schafer, G. The terminal quinol oxidase of the hyperthermophilic archaeon Acidianus ambivalens exhibits a novel subunit structure and gene organization. J. Bacteriol. 179 (1997) 1344-1353. [PMID: 9023221]

3. Gilderson, G., Aagaard, A., Gomes, C.M., Adelroth, P., Teixeira, M. and Brzezinski, P. Kinetics of electron and proton transfer during O2 reduction in cytochrome aa3 from A. ambivalens: an enzyme lacking Glu(I-286). Biochim. Biophys. Acta 1503 (2001) 261-270. [PMID: 11115638]

4. Komorowski, L., Verheyen, W. and Schafer, G. The archaeal respiratory supercomplex SoxM from S. acidocaldarius combines features of quinole and cytochrome c oxidases. Biol. Chem. 383 (2002) 1791-1799. [PMID: 12530544]

5. Muller, F.H., Bandeiras, T.M., Urich, T., Teixeira, M., Gomes, C.M. and Kletzin, A. Coupling of the pathway of sulphur oxidation to dioxygen reduction: characterization of a novel membrane-bound thiosulphate:quinone oxidoreductase. Mol. Microbiol. 53 (2004) 1147-1160. [PMID: 15306018]

6. Bandeiras, T.M., Pereira, M.M., Teixeira, M., Moenne-Loccoz, P. and Blackburn, N.J. Structure and coordination of CuB in the Acidianus ambivalens aa3 quinol oxidase heme-copper center. J. Biol. Inorg. Chem. 10 (2005) 625-635. [PMID: 16163550]

[EC created 2013 as EC, transferred 2018 to EC]

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