Glutathione Reductase(GR) is a flavoenzyme, each GR molecule contains 1 FAD molecule. Under hydrogen supplyment by co-enzyme NADPH, GR can catalyze oxidized glutathione (GSSG) to reduced glutathione (GSH). GSH keeps sulfydryl (-SH) containing enzymes in reduced & activated state, it maintains integrity of erythrocyte membranes and avoids hemoglobin oxidation.