This gene encodes a member of the family of pyridine nucleotide-disulfide oxidoreductases. This protein is a flavoenzyme, which uses NADPH for reduction of thioredoxins as well as other protein and nonprotein substrates, and plays a role in protection against oxidative stress. It contains a selenocysteine (Sec) residue, which is essential for catalytic activity. The selenocysteine is encoded by the UGA codon that normally signals translation termination. The 3' UTR of Sec-containing genes have a common stem-loop structure, the sec insertion sequence (SECIS), that is necessary for the recognition of UGA as a Sec codon, rather than as a stop signal. Alternative splicing of this gene results in several transcript variants encoding different isoforms. [provided by RefSeq, Jul 2008]