Methionine 5-oxides

Figure 6 HPLC separation of a 4.0-nmol mixture of blood thiols detected by CL. (1) IV-acetyl-L-cysteine (2) reduced glutathion (3) cysteine (4) methionine (5) oxidized glu-tathion. (From Ref. 95, with permission.)...

Primary amino groups remain untouched when methionine is oxidized to methionine 5-oxide in 97.5% yield by diethyl azodicarboxylate in aqueous ethanol at room temperature [979]. 

Experience has shown that the resolution by RPC methods of very closely related proteins, such as deamido forms, methionine 5-oxide, or N-terminal methionyl variants, is best achieved if mobile phase conditions can be chosen whereby the native structures of the proteins are preserved in the RPC system. The choice of these conditions frequently dictates that higher pH conditions, i.e., pH 4.5-7.5, are selected in these cases. To address these requirements and to take advantage of the ionization status of the amino acid side chains, a very large number of different ion-pairing reagents (including those already indicated... 

I2, AcOH, EtOH, 25°, 1 h, 100% yield. These conditions can result in methionine oxidation. ... 

McLafferty rearrangement 133, 163 Meisenheimer complexes 699, 702 Metal-chelated intermediates 838 Metal-halogen exchange 781, 784 Methionine, oxidation of 852-855 Methionine sulphone 853 Methionine sulphoxide 851-869 reduction of 1063 residues of... 

Chen et al. [47] demonstrated that the reaction of HOC1 with cytochrome c increased cytochrome peroxidase activity by the oxidation of the methionine residue. Methionine oxidation also significantly decreased the efficiency of cytochrome c as a mitochondrial electron carrier. HOC1, HOBr, and HOI are also able to oxidize (Fen)cytochrome c [48],... 

Griffiths S.W. and Cooney C.L. (2002), Relationship between protein structure and methionine oxidation in recombinant human alpha 1-antitrypsin, Biochemistry 41, 6245-6252. 

In this section we review the biochemicai studies that have been carried out on MsrB enzymes, and discuss some recent nutritionai studies that suggest zinc and seienium metaboiism may aiso affect methionine oxidation and in turn piay a major roie in aging. 

Although in humans only MsrBl is a selenoprotein, the depletion of selenium from the diet of mice led to increases in both R and S stereoisomers. This was not initially explained, yet a subsequent study has shown that small molecule selenols (organic selenocysteine homologues) could act as efficient electron donors in vitro for MsrA enzymes. ° This effect has only been shown in vitro, but the possibility that small molecular selenium reductants, or more likely that some selenoproteins that contain reduced selenols (in redox-active motifs) is quite intriguing. Several small selenoproteins do not have real roles and reside in nearly all subcompartments of the cell (mitochondria, ER) where electron donors for Msr enzymes are probably critical to maintain protein stability. Low selenium nutritional status would then have a significant impact on all methionine oxidation, as Future studies to address selenium nutrition and methionine oxidation could prove to be... 

This reductase, officially known as protein-methionine- -oxide reductase [EC 1.8.4.6], catalyzes the reaction of protein L-methionine with oxidized thioredoxin to yield protein L-methionine -oxide and reduced thioredoxin. Dithiothreitol can replace reduced thioredoxin in the reverse reaction. Free methionine is not a substrate however free methionine is similarly acted upon by an analogous reductase [EC 1.8.4.5]. 

Leong, S. L., Pham, C. L., Galatis, D., Eodero-Tavoletti, M. T., Perez, K., Hill, A. E., Masters, C. L., Ali, F. E., Barnham, K. J., and Cappai, R. (2009). Formation of dopamine-mediated alpha-synuclein-soluble oligomers requires methionine oxidation. Free Radio. Biol Med. 46,1328-1337. 

Lam XM, Yang JY, Cleland JL. Antioxidants for prevention of methionine oxidation in recombinant monoclonal antibody HER2. J Pharm Sci 1997 86(11) 1250—1255. 

Fransson JR. Oxidation of human insulin-like growth factor I in formulation studies. 3. Factorial experiments of the effects of ferric ions, EDTA, and visible light on methionine oxidation and covalent aggregation in aqueous solution. J Pharm Sci 1997 86(9) 4046-4050. 

Chao, C.-C., Ma, Y.-S., and Stadtman, E.R. 1997. Modification of protein surface hydrophobicity and methionine oxidation by oxidative systems. Proc. Nail. Acad. Sci. U.S.A. 94 2969-2974. 

Shao B, Oda MN, Bergt C, Fu X, Green PS, Biot N, Oram JF, Heinecke JW (2006) Myeloperoxidase Impairs ABCA1-Dependent Cholesterol Efflux through Methionine Oxidation and Site-Specific Tyrosine Chlorination of Apolipoprotein A-I. J Biol Chem 281 9001... 

Fixed modifications are modifications to specific amino acids that are considered to be complete—i.e., every occurrence of the amino acid in the sequence is assumed to carry the modification, and the unmodified amino acid is not considered. Variable modifications, on the other hand, are incomplete, and therefore both the modified and unmodified amino acid are considered in the search. In the example discussed above, the reduction/alkylation should result in complete carbamidomethylation of all cysteine residues thus, Carbamidomethyl (C) was chosen as a fixed modification, whereas methionine oxidation, a common artifac-tual modification that is usually incomplete, was selected as a variable modification The use of multiple variable modifications will greatly reduce the significance of any match and should therefore be used with caution. 

Superoxide dimutase inhibited both sulfite and methionine oxidation 4... 

This reaction is catalyzed by manganese ions at pH values from 6 to 7.5. S02 can also react with cystine to yield a series of oxidation products. Some of the possible reaction products resulting from the oxidation of sulfur amino acids are listed in Table 3-11. Nielsen et al. (1985) studied the reactions between protein-bound amino acids and oxidizing lipids. Significant losses occurred of the amino acids lysine, tryptophan, and histidine. Methionine was extensively oxidized to its sulfoxide. Increasing water activity increased losses of lysine and tryptophan but had no effect on methionine oxidation. 

In contrast, serpins which do not contain methionine residues immediate to the reactive centre (antithrombin III, PAI-2, PAI-3) are the least sensitive to oxidative inactivation [49 and refs, therein], PAI-2 is extremely insensitive to oxidative inactivation, which may be due to the absence of any oxidatively susceptible amino acids (i.e. methionine or cysteine) closely opposed to the reactive site and the failure of oxidants to modify the tertiary structure of PAI-2. Although ct2-antiplasmin has an active-site-associated methionine, oxidative... 

Fig. 10. The first step of methionine oxidation to methionine sulfoxide is reversible owing to methionine sulfoxide furtehr oxidation to methionine sulfone is irreversible.

Methionine oxidation inducing abolition of protein function usually does not produce any changes in chemical and immunochemical properties of the protein. This infers that the oxidized protein can be reactivated again by reduction of sulfoxide residue, or may be catabolized through its regular proteolytic pathway. Facility of methionine oxidation, along with abundant production of various oxidants, enables oxidation of methionine residues. This rises a question concerning... 

Cll. Ciorba, M. A., Heinemann, S. H., Weissbach, H., Brot, N., and Hoshi, T., Regulation of voltage-dependent K+ channels by methionine oxidation Effect of nitric oxide and vitamin C. FEBSLett. 442,48-52 (1999). 

Tl. Teh, L. C., Murphy, L. J., Huq, N. L., Surus, A. S., Friesen, H. G., etal., Methionine oxidation in human growth hormone and human chorionic somatomammotropin. Effects on receptor binding and biological activities. J. Biol. Chem. 262, 6472-6477 (1987). 

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