Maintains the sulfhydryl

As an anti-oxidant synthesized in the cell, GSH (reduced form) can provide hydrogen atom reversibly, with itself converted to GSSG (oxidized form) in the meantime. Reactions catalyzed by enzymes, such as GSH-Px (glutathione peroxidase), GST (glutathione S-transferase), etc., all need the involvement of GSH as a hydrogen donor.