Aqueous reactions oxidized glutathione

Figure 45-6. Interaction and synergism between antioxidant systems operating in the lipid phase (membranes) of the cell and the aqueous phase (cytosol). (R-,free radical PUFA-00-, peroxyl free radical of polyunsaturated fatty acid in membrane phospholipid PUFA-OOH, hydroperoxy polyunsaturated fatty acid in membrane phospholipid released as hydroperoxy free fatty acid into cytosol by the action of phospholipase Aj PUFA-OH, hydroxy polyunsaturated fatty acid TocOH, vitamin E (a-tocopherol) TocO, free radical of a-tocopherol Se, selenium GSH, reduced glutathione GS-SG, oxidized glutathione, which is returned to the reduced state after reaction with NADPH catalyzed by glutathione reductase PUFA-H, polyunsaturated fatty acid.)...

Ellison DH, Salmon GA, Wilkinson F (1972) Nanosecond pulse radiolysis of methanolic and aqueous solutions of readily oxidizable solutes. Proc R Soc Lond A 328 23-36 Erben-Russ M, Bors W, Saran M (1987) Reactions of linoleic acid peroxyl radicals with phenolic antioxidants a pulse radiolysis study. Int J Radiat Biol 52 393-412 Eriksen TE, Fransson G (1988) Radical-induced oxidation of glutathione in alkaline aqueous solution. Radiat Phys Chem 32 163-167... 

Previously, we have examined the formation of amino acid hydroperoxides following exposure to different radical species [100]. We observed that valine was most easily oxidised, but leucine and lysine are also prone to this modification in free solution. Scheme 12 illustrates the mechanism for formation of valine hydroperoxide. However, tertiary structure becomes an important predictor in proteins, where the hydrophobic residues are protected from bulk aqueous radicals, and lysine hydroperoxides are most readily oxidised. Hydroperoxide yield is poor from Fenton-derived oxidants as they are rapidly broken down in the presence of metal ions [101]. Like methionine sulphoxide, hydroperoxides are also subject to repair, in this case via glutathione peroxidase. They can also be effectively reduced to hydroxides, a reaction supported by the addition of hydroxyl radical in the presence of oxygen. Extensive characterisation of the three isomeric forms of valine and leucine hydroxides has been undertaken by Fu et al. [102,103], and therefore will not be discussed further here. 

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