GPX8 belongs to the glutathione peroxidase family. Glutathione peroxidase is an enzyme whose principal function is to protect against damage from endogenously-formed hydroxyperoxides, catalysing the reduction of hydroxyperoxides by glutathione. Several forms of the enzyme are known. It has a catalytic activity of 2 glutathione + H₂O2 = glutathione disulfide + 2 H₂O.