Alternative Oxidase family

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Last update: 2021-12-02 (Bruno Savelli)

Alternative Oxidase (AOX) and Plastid Terminal Oxidase (PTOX)


The alternative oxidase (AOX) is an enzyme that forms part of the electron transport chain in mitochondria of different organisms. The alternative oxidase is an integral monotopic membrane protein that is tightly bound to the inner mitochondrial membrane from matrix side. The enzyme has been predicted to contain a coupled diiron center on the basis of a conserved sequence motif consisting of the proposed iron ligands, four glutamate and two histidine amino acid residues. A catalytic cycle has been proposed that involves this di-iron center and at least one transient protein-derived free radical, which is probably formed on a tyrosine residue
Proteins homologous to the mitochondrial oxidase have also been identified in bacterial genomes. Multiple copies have been detected in plants which are not linked to oxidative phosphorylation and are located in the chloroplast.


Alternative Oxidase (AOX) :
Pfam: PF01786
Interpro: IPR002680
Alternative oxidase


McDonald A, Vanlerberghe G (2004). Branched mitochondrial electron transport in the Animalia: presence of alternative oxidase in several animal phyla. IUBMB Life 56 (6): 333–41. PMID: 15370881.
Sluse FE, Jarmuszkiewicz W (1998). Alternative oxidase in the branched mitochondrial respiratory network: an overview on structure, function, regulation, and role. Braz. J. Med. Biol. Res. 31 (6): 733-47. PMID: 9698817.
McDonald AE, Amirsadeghi S, Vanlerberghe GC (2003). Prokaryotic orthologues of mitochondrial alternative oxidase and plastid terminal oxidase. Plant Mol. Biol. 53 (6): 865-76. PMID: 15082931.
Atteia A, van Lis R, van Hellemond JJ, Tielens AG, Martin W, Henze K (2004). Identification of prokaryotic homologues indicates an endosymbiotic origin for the alternative oxidases of mitochondria (AOX) and chloroplasts (PTOX). Gene 330: 143-8. PMID: 15087133.
Berthold DA, Voevodskaya N, Stenmark P, Gräslund A, Nordlund P (2002). EPR studies of the mitochondrial alternative oxidase. Evidence for a diiron carboxylate center. J. Biol. Chem. 277 (46): 43608-14. PMID: 12215444.
Affourtit C, Albury MS, Crichton PG, Moore AL (2002). Exploring the molecular nature of alternative oxidase regulation and catalysis. FEBS Lett. 510 (3): 121-6. PMID: 11801238