Identification of a mitochondrial alcohol dehydrogenase in Schizosaccharomyces pombe: new insights into energy metabolism

Paul G. Crichton (1) , Charles Affourtit , Anthony L. Moore

1 Cellular Regulation

In this paper we show that mitochondria isolated from Schizosaccharomyces pombe exhibit antimycin A-sensitive oxygen uptake activity that is exclusively dependent on ethanol and is inhibited by trifluoroethanol, a potent inhibitor of alcohol dehydrogenase (ADH). Ethanol-dependent respiratory activity has, to our knowledge, not been reported in S. pombe mitochondria to date, and is indeed surprising as it has previously been concluded that only one ADH gene, encoding a cytosolic enzyme, occurs in this yeast. Spectrophotometric enzyme assays reveal that ADH activity in isolated mitochondria is increased ~ 16-fold by Triton X-100, which demonstrates the enzyme is located in the matrix. Using genetic knock-outs, we show conclusively that the novel mitochondrial ADH is encoded by adh4 and, as such, is unrelated to ADH isozymes found in mitochondria of other yeasts. By performing a modular-kinetic analysis of mitochondrial electron transfer, we furthermore show how ethanol-dependent respiratory activity (which involves oxidation of matrix-located NADH) compares to that observed when succinate or externally added NADH are used as substrates. This analysis reveals distinct kinetic differences between substrates which fully explain the lack of respiratory control generally observed during ethanol oxidation in yeast mitochondria.

Mots clés: Life Sciences

Paul G. Crichton, Charles Affourtit, Anthony L. Moore. Identification of a mitochondrial alcohol dehydrogenase in Schizosaccharomyces pombe: new insights into energy metabolism. Biochemical Journal, 2006, 401 (2), pp.459-464. ⟨10.1042/BJ20061181⟩. ⟨hal-00478644⟩