Thioredoxin reductase

Thioredoxin reductases (TR, TrxR) (EC 1.8.1.9) are the only known enzymes to reduce thioredoxin (Trx). Two classes of thioredoxin reductase have been identified: one class in bacteria and some eukaryotes and one in animals. Both classes are flavoproteins which function as homodimers. Each monomer contains a FAD prosthetic group, a NADPH binding domain, and an active site containing a redox-active disulfide bond.Structure of E. coli ThxR dimer bound thioredoxinStructure of E. coli ThxR with FAD and NADPH prosthetic groups labeledStructure of human ThxR FAD and NADPH prosthetic groups Thioredoxin reductases (TR, TrxR) (EC 1.8.1.9) are the only known enzymes to reduce thioredoxin (Trx). Two classes of thioredoxin reductase have been identified: one class in bacteria and some eukaryotes and one in animals. Both classes are flavoproteins which function as homodimers. Each monomer contains a FAD prosthetic group, a NADPH binding domain, and an active site containing a redox-active disulfide bond. Thioredoxin reductase is the only enzyme known to catalyze the reduction of thioredoxin and hence is a central component in the thioredoxin system. Together with thioredoxin (Trx) and NADPH this system's most general description is as a method of forming reduced disulfide bonds in cells. Electrons are taken from NADPH via TrxR and are transferred to the active site of Trx, which goes on to reduce protein disulfides or other substrates. The Trx system exists in all living cells and has an evolutionary history tied to DNA as a genetic material, defense against oxidative damage due to oxygen metabolism, and redox signaling using molecules like hydrogen peroxide and nitric oxide.