The interplay between sulphur and selenium metabolism in yeast influences the intracellular redox balance

Artikel i vetenskaplig tidskrift, 2012

Selenium is an essential element for most eukaryotic organisms, including humans. The balance between Se toxicity and its beneficial effects is very delicate. It has been demonstrated that a diet enriched of Se has cancer prevention potential in humans. The most popular commercial Se supplementation is selenized yeast, which is produced in a fermentation process using an inorganic source of Se. Here we show that uptake of Se, Se toxic effects and intracellular Se-metabolite profile are largely influenced by the level of sulphur source supplied during the fermentation. A Yap1-dependent oxidative stress response is active when yeast actively metabolizes Se and this response is linked to the generation of an intracellular redox imbalance. The redox imbalance derives from a disproportionate ratio between the reduced and oxidized form of glutathione and also from the influence of Se metabolism on the central carbon metabolism. The observed increase of glycerol production rate concomitant with the inhibition of ethanol formation in the presence of Se can be ascribed to the occurrence of redox imbalance that triggers glycerol biosynthesis to replenish the pool of NAD+.