The presence of a number of unidentified acidic peptides in extracts of calf lens was recorded by Waley (1956). Electrophoresis separated these compounds into a 'slow acid' fraction and a 'fast acid' fraction. The main new constituents of the former are ophthalmic acid (y-glutamyl-m-nbutyrylglycine) and norophthalmic acid (y-glutamylalanylglycine; Waley, 1957, 1958). The fast acid fraction was further subdivided into fractions called 1ca and 1 P. The main constituent of 1 a is S-sulphoglutathione (Waley, 1959). The present paper describes the identification of the main constituent of 1 P as S-(oxl-dicarboxyethyl)glutathione, i.e. GS * CH(C02H) O CH2-C02H, where GSH is glutathione. Lens extracts also contain the related amino acid, S-(cla-dicarboxyethyl)cysteine, i.e. CyS *CH(CO2H)-CH2-C02H, where CySH is cysteine. Neither the amino acid nor the peptide had previously been recognized as occurring in tissue extracts, although they had been prepared by Morgan & Friedmawn (1938). The amino acid was formed from cysteine and maleic acid and the peptide from GSH and maleic acid. The corresponding reactions proceed with fumaric acid, but are slower, and were not detected by Morgan & Friedmann (1938). EXPERIMENTAL Materiai8 S-(cfi-Dicarboxyethyl)cysteine. This was prepared by a method different from that used by Morgan & Friedmann (1938); the omission of inorganic salts facilitates the isolation of the amino acid. The same product was obtained from the reaction of either maleic acid (a) or fumaric acid (b) with cysteine, and was characterized as the bi8dicyciohexylamsne 8aU. (a) Dicyclohexylamine (2 ml.) was added to maleic acid (582.5 mg.) and L-cysteine hydrochloride (394 mg.) in water (5 ml.). The amine hydrochloride was removed by filtration, more dicyclohexylamine (0.5 ml.) was added and the solution diluted with acetone. The bisdicyclohexylamine salt of S-(cxP-dicarboxyethyl)cysteine (962 mg.) crystallized in needles, and after recrystallization from aqueous acetone had m.p. 1180 (Found: C,

No abstract

No abstract

No abstract

No abstract