Some derivatives of glutathione.

Although glutathione has been much studied, its oxidation products have not been adequately characterized. The first product of oxidation, the disulphide, GSSG, is a familiar compound, although it is doubtful whether it has been obtained pure. The kinetics of the reaction of GSSG with silver salts have been investigated (Cecil, 1950; Cecil & McPhee, 1957), but the product, the sulphinic acid, GSO2H, was not characterized. The final product of oxidation, the sulphonic acid, GSO3H, has also not been characterized. The thiolsulphonate, GS02 SG, was thought to be a product ofthe reaction ofGSSG with naphthalenesulphonyl chloride (Saunders 1933), but no convincing evidence of its existence has been put forward. The thiosulphate, GS * SO3H, which is found in lens extracts, was described by Waley (1959). Apart from their relevance to the chemistry of glutathione, compounds such as GSO2H represent bound forms of derivatives of cysteine which are intermediates in sulphur metabolism, and it is conceivable that the peptides also play a part in sulphur metabolism. This paper describes the preparation and properties of GSO2H, GSO3H and (probably) GS02 SG, and also gives some further properties of ophthalmic acid (y-glutamyl-a-amino-n-butyrylglycine), an analogue of glutathione in the lens (Waley, 1956, 1958). The sulphinic acid, GSO2H, was prepared by the reaction of silver nitrate with GSSG: