CHARACTERIZATION OF THE OXIDATION-PRODUCTS OF THE REACTION BETWEEN REDUCED GLUTATHIONE AND HYPOCHLOROUS ACID

Reduced glutathione (GSH) is one of the most preferred biological subs trates of myeloperoxidase-derived hypochlorous acid and is a likely ta rget for neutrophil oxidants. We have used HPLC to show that the oxida tion of GSH by hypochlorous acid gives two major, stable products in a ddition to glutathione disulphide (GSSG). The most prevalent product l acks free amine and thiol groups, and was shown by electrospray MS to have a molecular mass of 337 Da. This corresponds to GSH with a gain o f two oxygen atoms and a loss of two hydrogen atoms, and is consistent with the product being an internal sulphonamide. The other novel prod uct has a molecular mass of 644 Da, and has amine groups but no free t hiols. These properties are consistent with it being glutathione thiol sulphonate. Whereas GSSG in the cell is recycled enzymically, formatio n of these higher oxidation products is likely to be irreversible. Hyp ochlorous acid, therefore, could compromise the cell by depleting GSH. The putative sulphonamide may be unique for oxidation by hypochlorous acid and thus provide a useful marker of neutrophil oxidant activity.