ABSTRACT
The survival of any form of life depends upon a continuous supply of energy, usually provided by oxidation of nutrients. In most eukaryotic organisms, oxygen is the final acceptor for the reducing equivalents produced during these oxidations, becoming completely reduced to water in a reaction catalysed by the mitochondrial cytochrome oxidase. One exception to this rule is found in the bloodstream forms of African trypanosomes, in which electron transfer to oxygen is carried out by a KCN insensitive sn-glycerol-3-phosphate oxidase (also known as alternative oxidase), without cytochromes. Energy production in these cells depends only on glycolysis, and the role of the alternative oxidase is to oxidize glycerol 3-phosphate produced in the glycosome during the reoxidation of NADH (Grant and Sargent, 1960; and see Chapter 11). This system is located in the mitochondrial membrane (Fairlamb and Opperdoes, 1986), and uses ubiquinone Q9 as a redox intermediate between the glycerol-phosphate dehydrogenase and the terminal oxidase (Tielens and Hill, 1985; Turrens et al., 1986; Clarkson et al., 1989a).
