Methionine sulfoxide reductase, peptid

MsrA, thioredoxin-dependent peptide methionine sulfoxide reductase... 

Moskovitz J., Flescher E., Berlett B.S., Azare J., Poston J.M., and Stadtman E.R. (1998), Overexpression of peptide-methionine sulfoxide reductase in Saccharomy-ces cerevisiae and human T cells provides them with high resistance to oxidative stress, Proc. Nat. Acad. Sci. U.S.A. 95, 14071-14075. 

PEPTIDOMIMETIC COMPOUND PEPTIDE METHIONINE SULFOXIDE REDUCTASE... 

Qabbita SP, Aksenov MY, LoveU MA, Markesbery WR (1999) Decrease in peptide methionine sulfoxide reductase in Alzheimer s disease brain. J Neurochem 73 1660-1666 Geddes JW, Pang Z, Wiley DH (1996) Hippocampal damage and cytoskeletal disruption resulting from impaired energy metabolism. Implications for Alzheimer disease. Mol Chem Neuropathol 28 65-74... 

Moreover, formation of radical transients with S.-.O bonds is kinetically preferred, but on longer time scale they convert into transients with S.-.N bonds in a pH dependent manner. Ultimately transients with S.-.N bonds transform intramolecularly into C-centred radicals located on the C moiety of the peptide backbone. Another type of C-centred radicals located in the side chain of Met-residue, a-(aikylthio)alkyl radicals, are formed via deprotonation of MetS +. C-centred radicals are precursors for peroxyl radicals (ROO ) that might be involved in chain reactions of peptide and/or protein oxidation. Stabilization of MetS +through formation of S.-.O- and S.-.N-bonded radicals might potentially accelerate oxidation and autooxidation processes of Met in peptides and proteins. Considering that methionine sulfoxide, which is the final product coming from all radicals centred on sulphur, is restored by the enzyme methionine sulfoxide reductase into MetS, stabilization of MetS +appears as a protection against an eventual peroxidation chain that would develop from a carbon centred radical. 

Besides thiol repair there also exists direct repair for one of the oxidation products of methionine, methionine sulfoxide. The enzyme peptide methionine sulfoxide reductase reduces the methionine sulfoxide formed in proteins due to oxidation and is therefore able to reconstitute the normal protein (Fig. 3). Besides methionine sulfoxide there exists a further oxidation product of methionine, methionine sulfone, which can not be repaired. The cycle of methionine oxidation and efficient methionine sulfoxide repair, and the early and easy oxidation of the methionine in proteins, led some authors to hypothesize that methionine acts as an intramolecular antioxidant for some proteins and so protects other amino acids from oxidation [12]. Besides the peptide methionine sulfoxide reductases, there also exists methionine reductases able to... 

GUSTAVSSON, N., KOKKE, B.P., HARNDAHL, U., SILOW, M., BECHTOLD, U., POGHOSYAN, Z., MURPHY, D., BOELENS, W.C., SUNDBY, C., A peptide methionine sulfoxide reductase highly expressed in photosynthetic tissue in Arabidopsis thaliana can protect the chaperone-like activity of a chloroplast-localized small heat shock protein., Plant J.. 2002, 29, 545-553. 

Ruan H, Tang XD, Chen ML et al. (2002) High-quality life extension by the enzyme peptide methionine sulfoxide reductase. Proc Natl Acad Sci USA 99(5), 2748-2753. 

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