Glutathione reductase （GR） is a member of pyridine nucleotide-disulfide oxidoreductases，which includes the closely related enzymes thioredoxin reductase，lipoamide dehydrogenase，trypanothione reductase and mercuric ion reductase. GR is a cytoplasmic flavoenzyme widely distributed in aerobic organisms. The dimeric protein is composed of two identical subunits，each containing 1 FAD and 1 redox-active disulfide/dithiol as components of the catalytic apparatus. It plays a role in maintaining glutathione （GSH） in its reduced form by catalyzing the reduction of glutathione disulfide （GSSG）. In most eukaryotic cells，GR maintains the ratio of [GSH]/[GSSG] elevated，and participates in several vital functions such as the detoxification of reactive oxygen species as well as protein and DNA biosynthesis.
