FUNCTION Maintains high levels of reduced glutathione in the cytosol.CATALYTIC ACTIVITY 2 glutathione + NADP(+) = glutathione disulfide + H(+) + NADPHCOFACTOR Binds 1 FAD per subunit.SUBUNIT Homodimer; disulfide-linked.SUBCELLULAR LOCATION Each subunit can be divided into 4 domains that are consecutive along the polypeptide chain. Domains 1 and 2 bind FAD and NADPH, respectively. Domain 4 forms the interface.DISEASE The disease is caused by variants affecting the gene represented in this entry.MISCELLANEOUS The active site is a redox-active disulfide bond.MISCELLANEOUS Produced by alternative initiation of isoform Mitochondrial.MISCELLANEOUS Expressed at very high levels in peripheral blood.SIMILARITY Belongs to the class-I pyridine nucleotide-disulfide oxidoreductase family.SEQUENCE CAUTION Glutathione reductase entry