Metabolism of selenium in Saccharomyces cerevisiae and improved biosynthesis of bioactive organic Se-compounds

Conference poster, 2010

Selenium (Se) is an essential element for many organisms as it is present under the form of Se-cysteine in Se-proteins. 25 Se-proteins are known in humans and are all involved in protection of cells from oxidative stress. The main sources of Se for animals are edible plants able to accumulate Se from the soil in inorganic and organic forms. Some of the Se organic forms bioavailable for animals have been proven to have cancer-preventing effects if regularly introduced into the diet. Since Se content in plants is highly susceptible to environmental factors, the intake of Se is often insufficient to result in beneficial effects. Therefore, the use of Se-enriched yeast as food supplement is made available to avoid Se shortage. The yeast Saccharomyces cerevisiae does not require Se as essential element, but is able to metabolise and accumulate Se. Due to the very similar properties of Se and sulphur (S), S- and Se-compounds share the same assimilation and metabolic routes, but the competition is in favour of S-species, as the high reactivity of Se leads to the formation of toxic compounds. Due to the delicate balance between beneficial and toxic effects of Se, the study of Se metabolism in yeast is a crucial point towards the establishment of a yeast cell factory for the production of bioactive Se-compounds. The present study shows how the presence of Se influences cell physiology and metabolism. On this basis, we show how the coupling of metabolic engineering and bioprocess optimization represents a successful strategy towards the production of organic Se-molecule with high anti-cancer potential. The Se-metabolome has been carefully mapped.