Studies of Cyanide-Resistat Respiratrion in the Yeast, Hansenula anomala

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The cyanide-resistant respiration was reported in a variety of organisms, including higher plants, and microorganisms. This pathway was also found zoomatigophoria, Trypanosoma brucei brucei. The pathway consists of a branching from the conventional electron transport system at CoQ site catalyzed by a specific "alternative oxidase" distinct from cytochrome oxidase. However, the physiological role remains unknown, and the characterization of the enzyme is still incomplete. In the yeast, Hansenula anomala, we found the rapid induction of the cyanide-resistant respiration with some respiratory inhibitors, cloned cDNA for the alternative oxidase, and deduced the amino acid sequence from the nucleotide sequence of the cDNA.Our finding in this research project are as follows :(1) A monoclonal antibody against the alternative oxidase in the plant cross-reacted with the enzyme from H.anomala. There was a similarity in the amino acid sequence between these enzymes.(2) Several nitrogen bases such as benzo- (h) -quinoline, with no chelating ability, were potent inbitors of cyanide resistant respiration of mitochondria isolated from H.anomala.(3) When the electron transport of the mitochondria from H.anomala was blocked at Q site of Q-cycle, O_2 generation was increased. Both O_2 generation and the induction of cyanide-resistant respiration were suppressed by radical scavengers, suggesting that O_2 might play a role in the signal formation toward nuclei to express the alternative oxidase gene.(4) An antibiotic, ascofuranone, specifically inhibits glycerol-3-phosphate dehydrogenase site in the mitochondria electron transport system from Trypanosoma brucei brucei, a protozoan parasite responsible for sleeping sickeness, and in combination with glycerol ascofuranone showed a potent inhibition on the in vitro growth of the parasite.