The biological significance of methionine sulfoxide stereochemistry

Byung Cheon Lee, Vadim N. Gladyshev

Research output: Contribution to journalReview articlepeer-review

104 Citations (Scopus)


Methionine can be oxidized by reactive oxygen species to a mixture of two diastereomers, methionine-S-sulfoxide and methionine-R-sulfoxide. Both free amino acid and protein-based forms of methionine-S-sulfoxide are stereospecifically reduced by MsrA, whereas the reduction of methionine-R-sulfoxide requires two enzymes, MsrB and fRMsr, which act on its protein-based and free amino acid forms, respectively. However, mammals lack fRMsr and are characterized by deficiency in the reduction of free methionine-R-sulfoxide. The biological significance of such biased reduction of methionine sulfoxide has not been fully explored. MsrA and MsrB activities decrease during aging, leading to accumulation of protein-based and free amino acid forms of methionine sulfoxide. Since methionine is an indispensible amino acid in human nutrition and a key metabolite in sulfur, methylation, and transsulfuration pathways, the consequences of accumulation of its oxidized forms require further studies. Finally, in addition to methionine, methylsulfinyl groups are present in various drugs and natural compounds, and their differential reduction by Msrs may have important therapeutic implications.

Original languageEnglish
Pages (from-to)221-227
Number of pages7
JournalFree Radical Biology and Medicine
Issue number2
Publication statusPublished - 2011 Jan 15
Externally publishedYes


  • Methionine sulfoxide
  • Methionine, Methionine sulfoxide reductase
  • Methylsulfinyl-containing compounds
  • MsrA
  • MsrB
  • Sulfur metabolism
  • fRMsr

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)


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