IUBMB Enzyme Nomenclature


Accepted name: peptide-methionine (R)-S-oxide reductase

Reaction: peptide-L-methionine + thioredoxin disulfide + H2O = peptide-L-methionine (R)-S-oxide + thioredoxin

For diagram click here and mechanism click here.

Other name(s): 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; pRMsr

Systematic name: peptide-methionine:thioredoxin-disulfide S-oxidoreductase [methionine (R)-S-oxide-forming]

Comments: The reaction occurs in the reverse direction to that shown above. The enzyme exhibits high specificity for reduction of the R-form of methionine S-oxide, with higher activity being observed with L-methionine S-oxide than with D-methionine S-oxide [9]. While both free and protein-bound methionine (R)-S-oxide act as substrates, the activity with the peptide-bound form is far greater [10]. The enzyme plays a role in preventing oxidative-stress damage caused by reactive oxygen species by reducing the oxidized form of methionine back to methionine and thereby reactivating peptides that had been damaged. In some species, e.g. Neisseria meningitidis, both this enzyme and EC, peptide-methionine (S)-S-oxide reductase, are found within the same protein whereas in other species, they are separate proteins [3,5]. The reaction proceeds via a sulfenic-acid intermediate [5,10]. For MsrB2 and MsrB3, thioredoxin is a poor reducing agent but thionein works well [11]. The enzyme from some species contains selenocysteine and Zn2+.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. Moskovitz, J., Singh, V.K., Requena, J., Wilkinson, B.J., Jayaswal, R.K. and Stadtman, E.R. Purification and characterization of methionine sulfoxide reductases from mouse and Staphylococcus aureus and their substrate stereospecificity. Biochem. Biophys. Res. Commun. 290 (2002) 62-65. [PMID: 11779133]

2. Taylor, A.B., Benglis, D.M., Jr., Dhandayuthapani, S. and Hart, P.J. Structure of Mycobacterium tuberculosis methionine sulfoxide reductase A in complex with protein-bound methionine. J. Bacteriol. 185 (2003) 4119-4126. [PMID: 12837786]

3. Singh, V.K. and Moskovitz, J. Multiple methionine sulfoxide reductase genes in Staphylococcus aureus: expression of activity and roles in tolerance of oxidative stress. Microbiology 149 (2003) 2739-2747. [PMID: 14523107]

4. Boschi-Muller, S., Olry, A., Antoine, M. and Branlant, G. The enzymology and biochemistry of methionine sulfoxide reductases. Biochim. Biophys. Acta 1703 (2005) 231-238. [PMID: 15680231]

5. Ezraty, B., Aussel, L. and Barras, F. Methionine sulfoxide reductases in prokaryotes. Biochim. Biophys. Acta 1703 (2005) 221-229. [PMID: 15680230]

6. Weissbach, H., Resnick, L. and Brot, N. Methionine sulfoxide reductases: history and cellular role in protecting against oxidative damage. Biochim. Biophys. Acta 1703 (2005) 203-212. [PMID: 15680228]

7. Kauffmann, B., Aubry, A. and Favier, F. The three-dimensional structures of peptide methionine sulfoxide reductases: current knowledge and open questions. Biochim. Biophys. Acta 1703 (2005) 249-260. [PMID: 15680233]

8. Vougier, S., Mary, J. and Friguet, B. Subcellular localization of methionine sulphoxide reductase A (MsrA): evidence for mitochondrial and cytosolic isoforms in rat liver cells. Biochem. J. 373 (2003) 531-537. [PMID: 12693988]

9. Olry, A., Boschi-Muller, S., Marraud, M., Sanglier-Cianferani, S., Van Dorsselear, A. and Branlant, G. Characterization of the methionine sulfoxide reductase activities of PILB, a probable virulence factor from Neisseria meningitidis. J. Biol. Chem. 277 (2002) 12016-12022. [PMID: 11812798]

10. Boschi-Muller, S., Olry, A., Antoine, M. and Branlant, G. The enzymology and biochemistry of methionine sulfoxide reductases. Biochim. Biophys. Acta 1703 (2005) 231-238. [PMID: 15680231]

11. Sagher, D., Brunell, D., Hejtmancik, J.F., Kantorow, M., Brot, N. and Weissbach, H. Thionein can serve as a reducing agent for the methionine sulfoxide reductases. Proc. Natl. Acad. Sci. USA 103 (2006) 8656-8661. [PMID: 16735467]

[EC created 2006]

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