Reaction: 2 ubiquinol + O2 = 2 ubiquinone + 2 H2O
Other name(s): plant alternative oxidase; cyanide-insensitive oxidase; AOX (gene name); ubiquinol oxidase; ubiquinol:O2 oxidoreductase (non-electrogenic)
Systematic name: ubiquinol:oxygen oxidoreductase (non-electrogenic)
Comments: The enzyme, described from the mitochondria of plants and some fungi and protists, is an alternative terminal oxidase that is not sensitive to cyanide inhibition and does not generate a proton motive force. Unlike the electrogenic terminal oxidases that contain hemes (cf. EC 1.10.3.10 and EC 1.10.3.14), this enzyme contains a dinuclear non-heme iron complex. The function of this oxidase is believed to be dissipating excess reducing power, minimizing oxidative stress, and optimizing photosynthesis in response to changing conditions.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Bendall, D.S. and Bonner, W.D. Cyanide-insensitive respiration in plant mitochondria. Plant Physiol. 47 (1971) 236-245. [PMID: 16657603]
2. Siedow, J.N., Umbach, A.L. and Moore, A.L. The active site of the cyanide-resistant oxidase from plant mitochondria contains a binuclear iron center. FEBS Lett. 362 (1995) 10-14. [PMID: 7698344]
3. Berthold, D.A., Andersson, M.E. and Nordlund, P. New insight into the structure and function of the alternative oxidase. Biochim. Biophys. Acta 1460 (2000) 241-254. [PMID: 11106766]
4. Williams, B.A., Elliot, C., Burri, L., Kido, Y., Kita, K., Moore, A.L. and Keeling, P.J. A broad distribution of the alternative oxidase in microsporidian parasites. PLoS Pathog. 6 (2010) e1000761. [PMID: 20169184]
5. Gandin, A., Duffes, C., Day, D.A. and Cousins, A.B. The absence of alternative oxidase AOX1A results in altered response of photosynthetic carbon assimilation to increasing CO2 in Arabidopsis thaliana. Plant Cell Physiol 53 (2012) 1627-1637. [PMID: 22848123]