Glutathione Peroxidase Activity as a Function of Dietary Selenomethionine

SINCE 1957, selenium has been recognized as an essential micronutrient for animals, but its exact biological function has remained uncertain. The metabolic role of selenium in animals seems to be linked with vitamin E and sulphur amino acids1–4. Selenium has a sparing effect on vitamin E, and delays the onset of deficiency syndromes. Likewise, vitamin E and sulphur amino acids partially protect against or delay the onset of several forms of selenium deficiency syndromes. Rotruck et al.5proposed that selenium functions as an integral part of glutathione (GSH) peroxidase, an enzyme that reduces toxic lipid peroxides to hydroxy acids6–8. They found that a large proportion of the 75Se from rat erythrocytes labelled in vivo remained with the enzyme during extensive purification, and more recently, their studies with highly purified GSH peroxidase have indicated that it contains approximately 4 mol of Se per mol of enzyme9. Similar findings were reported by Flohé et al. for bovine erythrocyte GSH peroxidase10. To learn more about the nutritional relationship between selenium and GSH peroxidase, we performed studies that showed GSH peroxidase activity is proportional to dietary selenium, which provided additional evidence for the role of selenium in the function of GSH peroxidase.