The alternative oxidase is a membrane-bound enzyme capable of supporting cyanide-and antimycin A-resistant mitochondrial respiration. It catalyzes the oxidation of ubiquinol and the reduction of oxygen to water in a four electron process. As this bypasses several proton-translocating steps, inducton of this alternative pathway is associated with a dramatic reduction of ATP production. Expression and activity of the enzyme is modified by environmental conditions such as temperature, oxidative stress, nutrient availability, as well as by pathogens such as viruses. AOX can be found in most plants, many fungi and protists, but is not expressed in animals.
Reference: Young 2013 Biochem Soc Trans
MitoPedia topics: Enzyme