Selenium in Biocatalysis

Selenium has long been considered a toxic element. Its toxicity has been attributed to its incorporation into the amino acids cysteine and methionine in place of sulfur. This incorporation results in an alteration in the structure of proteins which directly affects its function. Today it is well documented that at low concentrations, selenium is an essential element. The discovery of several prokaryotic and eukaryotic proteins that contain selenium as the amino acid selenocysteine or as an unstable perselenide adduct demonstrated that selenium is directly involved in biocatalysis. Keywords: selenium; selenocysteine; selenoprotein