Journal of Bioenergetics and Biomembranes

, Volume 27, Issue 4, pp 379–385

Regulation of alternative oxidase activity in higher plants

  • David A. Day
  • Joseph T. Wiskich

DOI: 10.1007/BF02110000

Cite this article as:
Day, D.A. & Wiskich, J.T. J Bioenerg Biomembr (1995) 27: 379. doi:10.1007/BF02110000


Plant mitochondria contain two terminal oxidases: cytochrome oxidase and the cyanideinsensitive alternative oxidase. Electron partioning between the two pathways is regulated by the redox poise of the ubiquinone pool and the activation state of the alternative oxidase. The alternative oxidase appears to exist as a dimer which is active in the reduced, noncovalently linked form and inactive when in the oxidized, covalently linked form. Reduction of the oxidase in isolated tobacco mitochondria occurs upon oxidation of isocitrate or malate and may be mediated by matrix NAD(P)H. The activity of the reduced oxidase is governed by certain other organic acids, notably pyruvate, which appear to interact directly with the enzyme. Pyruvate alters the interaction between the alternative oxidase and ubiquinol so that the oxidase becomes active at much lower levels of ubiquinol and competes with the cytochrome pathway for electrons. These requirements for activation of the alternative oxidase constitute a sophisticated feed-forward control mechanism which determines the extent to which electrons are directed away from the energy-conserving cytochrome pathway to the non-energy conserving alternative oxidase. Such a mechanism fits well with the proposed role of the alternative oxidase as a protective enzyme which prevents over-reduction of the cytochrome chain and fermentation of accumulated pyruvate.

Key words

Plant mitochondriaalternative oxidaseelectron transportprotein disulfide bondsenzyme activation

Copyright information

© Plenum Publishing Corporation 1995

Authors and Affiliations

  • David A. Day
    • 1
  • Joseph T. Wiskich
    • 2
  1. 1.Division of Biochemistry and Molecular Biology, and the Cooperative Research Centre in Plant ScienceAustralian National UniversityCanberra
  2. 2.Botany DepartmentUniversity of AdelaideAdelaideAustralia