Accumulation and metabolism of selenium by yeast cells

Abstract

This paper examines the process of selenium bioaccumulation and selenium metabolism in yeast cells. Yeast cells can bind elements in ionic from the environment and permanently integrate them into their cellular structure. Up to now, Saccharomyces cerevisiae, Candida utilis, and Yarrowia lipolytica yeasts have been used primarily in biotechnological studies to evaluate binding of minerals. Yeast cells are able to bind selenium in the form of both organic and inorganic compounds. The process of bioaccumulation of selenium by microorganisms occurs through two mechanisms: extracellular binding by ligands of membrane assembly and intracellular accumulation associated with the transport of ions across the cytoplasmic membrane into the cell interior. During intracellular metabolism of selenium, oxidation, reduction, methylation, and selenoprotein synthesis processes are involved, as exemplified by detoxification processes that allow yeasts to survive under culture conditions involving the elevated selenium concentrations which were observed. Selenium yeasts represent probably the best absorbed form of this element. In turn, in terms of wide application, the inclusion of yeast with accumulated selenium may aid in lessening selenium deficiency in a diet.

Fig. 1

Pathway of reduction of selenium in yeast cells (Hoefig et al. ; Kitajima and Chiba ; Mapelli et al. 2011). a Sulfurylase ATP; b kinase APSe; c reductase PAPSe; d sulphate reductase

Fig. 2

Transformation SeO ₃^2 − with the participation of glutatione

Fig. 3

Schematic overview of the metabolism of the different selenocompounds in yeast (Hoefig et al. ; Kitajima and Chiba ; Mapelli et al. 2011). a Homocysteine synthase; b methionine synthase; c synthase adenosylomethionine; d methyltransferase; e hydrolase adenosylhomocysteine; f cystathionine-β-synthase; g cystathionine-γ-lyase; h Se-methyltransferase; i synthase γ-glu-Cys

Fig. 4

Selenocysteine biosynthesis in yeast cells (Allmang et al. ; Squires and Berry ; Turanov et al. ; Xu et al. 2007)

Fig. 5

Selenoprotein biosynthesis in yeast cells (Allmang et al. ; Small-Howard et al. ; Squires and Berry 2008)