Methionine sulfoxide

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Methionine sulfoxide
Methionine sulfoxide.png
IUPAC name
2-Amino-4-(methylsulfinyl)butanoic acid
ChemSpider 824
Jmol-3D images Image
PubChem 847
Molar mass 165.21 g·mol−1
Appearance white solid
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Methionine sulfoxide is the organic compound with the formula CH3S(O)CH2CH2CH(NH2)CO2H. It is an amino acid that occurs naturally although it is formed post-translationally.

Oxidation of the sulfur of methionine results in methionine sulfoxide or methionine sulfone. The sulfur-containing amino acids methionine and cysteine are more easily oxidized than the other amino acids.[1] Unlike oxidation of other amino acids, the oxidation of methionine can be reversed by enzymatic action, specifically by enzymes in the methionine sulfoxide reductase family of enzymes. The three known methionine sulfoxide reductases are MsrA, MsrB, and fRmsr.[1] Oxidation of methionine results in a mixture of the two diastereomers methionine-S-sulfoxide and methionine-R-sulfoxide, which are reduced by MsrA and MsrB, respectively.[2] MsrA can reduce both free and protein-based methionine-S-sulfoxide, whereas MsrB is specific for protein-based methionine-R-sulfoxide. fRmsr, however, catalyzes the reduction of free methionine-R-sulfoxide.[1] Thioredoxin serves to recycle by reduction some of the methionine sulfoxide reductase family of enzymes, whereas others can be reduced by metallothionein.[3]

Biochemical Function[edit]

Methionine sulfoxide increases with age in body tissues, which is believed to contribute to ageing.[4][5] Transgenic Drosophila (fruit flies) that overexpress methionine sulfoxide reductase show extended lifespan.[6] Methionine sulfoxide (Met(o)) is the oxidized form of amino acid methionine (Met). The oxidation of methionine serves as a switch that deactivates certain protein activities such as E.coli ribosomal protein, L12.[7] Protein with great amount of methionine residues tend to exist within the lipid bilayer as methionine is one of the most hydrophobic amino acid. Those methionine residues that are exposed to the aqueous exterior thus are vulnerable to oxidation.2 The oxidized residues tend to be arrayed around the active site and may guard access to this site by reactive oxygen species. Once oxidized, the met(o) residues are reduced back to methionine by the enzyme methionine sulfoxide reductase.3 Thus, an oxidation–reduction cycle occurs in which exposed methionine residues are oxidized (e.g., by H2O2) to methionine sulfoxide residues, which are subsequently reduced.[8]
Methionine(protein)+ H2O2→ Methionine Sulfoxide(protein)+ H2O
Methionine Sulfoxide(protein)+ NADPH+H+→ Methionine(protein)+ NADP++H2O

See also[edit]


  1. ^ a b c Lee BC, Dikiy A, Kim HY, Gladyshev VN (2009). "Functions and evolution of selenoprotein methionine sulfoxide reductases". BIOCHEMICA ET BIOPHYSICA ACTA 1790 (11): 1471–1477. doi:10.1016/j.bbagen.2009.04.014. PMC 3062201. PMID 19406207. 
  2. ^ Kim HY, Gladyshev VN (2004). "Methionine sulfoxide reduction in mammals: characterization of methionine-R-sulfoxide reductases". MOLECULAR BIOLOGY OF THE CELL 15 (3): 1055–1064. doi:10.1091/mbc.E03-08-0629. PMC 363075. PMID 14699060. 
  3. ^ Sagher D, Brunell D, Hejtmancik JF, Kantorow M, Brot N, Weissbach H (2006). "Thionein can serve as a reducing agent for the methionine sulfoxide reductases". Proceedings of the National Academy of Sciences of the United States of America 103 (23): 8656–8661. doi:10.1073/pnas.0602826103. PMC 1592241. PMID 16735467. 
  4. ^ Stadtman ER, Van Remmen H, Richardson A, Wehr NB, Levine RL (2005). "Methionine oxidation and aging". BIOCHEMICA ET BIOPHYSICA ACTA 1703 (2): 135–140. doi:10.1016/j.bbapap.2004.08.010. PMID 15680221. 
  5. ^ Shringarpure R, Davies KJ (2002). "Protein turnover by the proteasome in aging and disease". FREE RADICAL BIOLOGY & MEDICINE 32 (11): 1084–1089. doi:10.1016/S0891-5849(02)00824-9. PMID 12031893. 
  6. ^ Ruan H, Tang XD, Chen ML, Joiner ML, Sun G, Brot N, Weissbach H, Heinemann SH, Iverson L, Wu CF, Hoshi T (2002). "High-quality life extension by the enzyme peptide methionine sulfoxide reductase". Proceedings of the National Academy of Sciences of the United States of America 99 (5): 2748–2753. doi:10.1073/pnas.032671199. PMC 122419. PMID 11867705. 
  7. ^ Brot, N; Weissbach, L; Werth, J; Weissbach, H (April 1981). "Enzymatic reduction of protein-bound methionine sulfoxide.". Proceedings of the National Academy of Sciences of the United States of America 78 (4): 2155–8. doi:10.1073/pnas.78.4.2155. PMC 319302. PMID 7017726. 
  8. ^ Levine, RL; Mosoni, L; Berlett, BS; Stadtman, ER (Dec 24, 1996). "Methionine residues as endogenous antioxidants in proteins.". Proceedings of the National Academy of Sciences of the United States of America 93 (26): 15036–40. doi:10.1073/pnas.93.26.15036. PMC 26351. PMID 8986759. 

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