Define about the Glutathione peroxidases - Selenium?

The role of selenium in the cytosolic enzyme, glutathione peroxidase (GSHPx), was first illustrated in 1973. Four selenium dependent glutathione peroxidases have been identified and named as Glutathione peroxidases 1-4 (GSHP_xs 1-4). During stress, infection, or tissue injury, selenoenzymes may protect against the damaging effects of hydrogen peroxide or oxygen-rich free radicals. This family of enzymes catalyzes the destruction of hydrogen peroxide or lipid hydroperoxides according to the following general reactions:

H₂O₂ + 2GSH → 2H₂O + GSSG

ROOH + 2GSH → ROH + H₂O + GSSG

Where, GSH is glutathione and GSSG is its oxidized form.

Thus, from the reaction above, it is evident that the main role of glutathione peroxidases is to reduce hydrogen .peroxide and free hydroperoxides in different cells and tissues by using glutathione (GSH) as the hydrogen donor. Thus, the reactive species of hydroperoxide free radicals are converted into innocuous molecules of water. GSHP_x-l is present in virtually all cells, GSHP_x-2 is localized in the gastrointestinal tract, and GSHP_x-3 is present in plasma while GSHP_x-4 is most abundant in testis but present in other tissues also. GSrn4plays a major role in protecting against lipid peroxidation as it is the only intracellular enzyme that can reduce fatty acid hydro peroxide, GSHP_x-3 in plasma can also perform this role.