Induction of cytochrome P-450 and ethanol oxidation in Yarrowia lipolytica

The study of the effect of different ethanol concentrations in the medium on the growth and the activity of enzymatic systems involved in ethanol oxidation in Yarrowia lipolytica showed that the cultivation of yeast cells on 1 and 2% ethanol caused their rapid growth and a drastic increase in cell respiration and sensitivity to cyanide already in the first hours of cultivation. At the same time, during cultivation on 3, 4, and 5% ethanol, the growth and respiration of yeast cells were considerably suppressed. All of the ethanol concentrations studied induced the synthesis of cytochrome P-450, its dynamics in cells being dependent on the initial concentration of ethanol in the medium. When the initial concentration of ethanol was 1 and 2%, the content of cytochrome P-450 in cells steeply decreased after a short period of induction. But when the initial concentration of ethanol in the medium was 3 to 5%, the content of cytochrome P-450 in cells was high throughout the cultivation period. The induction of cytochrome P-450 in cells preceded the induction of the NAD-dependent enzymes alcohol dehydrogenase and catalase, which, like cytochrome P-450, are also involved in ethanol oxidation by yeasts. The activity of catalase was higher in the yeast cells grown in the presence of 3 to 5% ethanol than in the cells grown in the presence of 1 and 2% ethanol. The roles played by cytochrome P-450, alcohol dehydrogenase, and catalase in ethanol oxidation by yeast cells are discussed.