In enzymology, a peptide-methionine (R)-S-oxide reductase () is an enzyme that catalyzes the chemical reaction peptide-L-methionine + thioredoxin disulfide + H2O peptide-L-methionine (R)-S-oxide + thioredoxin The 3 substrates of this enzyme are peptide-L-methionine, thioredoxin disulfide, and H2O, whereas its two products are peptide-L-methionine (R)-S-oxide and thioredoxin. This enzyme belongs to the family of oxidoreductases, specifically those acting on a sulfur group of donors with a disulfide as acceptor. The systematic name of this enzyme class is peptide-methionine:thioredoxin-disulfide S-oxidoreductase [methionine (R)-S-oxide-forming]. Other names in common use include MsrB, methionine sulfoxide reductase (ambiguous), pMSR, methionine S-oxide reductase (ambiguous), selenoprotein R, methionine S-oxide reductase (R-form oxidizing), methionine sulfoxide reductase B, SelR, SelX, PilB, and pRMsr. References EC 1.8.4 Enzymes of unknown structure Selenoproteins