Thioredoxin reductase peptide, corresponding to residues 53-67 in thioredoxin reductase (TrxR), is used in thioredoxin reductase research. Mammalian thioredoxin reductase (TR) catalyzes the reduction of the redox-active disulfide bond of thioredoxin (Trx) and is structurally and mechanistically similar to glutathione reductase, except for a C-terminal 16-amino acid extension containing a rare vicinal selenylsulfide bond.