Glutathione reductase (GLR1) exists in mitochondrial and cytoplasmic isoforms. It shares sequence and structural homology to thioredoxin reductase, and is a flavin-containing oxidoreductase. Its active site is composed of a redox-active disulphide, and it requires NADPH for its catalytic activity. It is a widely present enzyme and is found in plants, bacteria, yeast, mice and humans.
Glutathione reductase IGR) is a crucial flavoenzyme in the antioxidant defense system. Reduced glutathione (GSH) is used by glutathione peroxidase to detoxify hydrogen peroxide and in the process is converted to oxidized glutathione (GSSG). The GSSG is then recycled back to GSH by glutathione reductase (GR) using NADPH that is then converted to NADP+. The regenerated GSH is then available to detoxify more hydrogen peroxide. The enzyme uses FAD as a cofactor. GR and glutathione peroxidase may inhibit lipid peroxidation by functioning as antioxidant enzymes in sperm. Glutathione reductase shares a structural motif with a number of other proteins including aspartyl proteases, citrate synthase, EF hands, hemoglobins, lipocalins, and α/β hydrolases. GR is stimulated by melatonin and is reportedly irreversibly inhibited by a number of oxygen radical generating systems.
