Selenium-containing compounds in baker's yeast (Saccharomyces cerevisiae)

The distribution of selenium in subcellular fractions of Saccharomyces cerevisiae was investigated after cultivation of the yeast cells in a medium with added Se-75-selenite. The major part of the tracer taken up by the cells was contained in loosely bound small compounds with molecular masses below 1 kDa, present on the cell walls and the outer membranes of the mitochondrial and microsomal fractions. After separation of the proteins in the subcellular fractions by means of SDS-PAGE a Se-75-containing cytosolic protein band with the molecular mass of 25 kDa was found, which migrated with the same velocity as the GSH-Px subunit isolated from rat liver. As the yeast cytosol showed enzymatic glutathione peroxidase activity, the results might suggest that the selenium-containing 25 kDa-protein in Saccharomyces cerevisiae is similar to the GSH-Px subunit.