Figure 1. Schematic representation of γ-glutamyl cycle in the bovine lens epithelial-cortical layer. Numbers refer to enzymes involved in the cycle. 1: γ-glutamyltransferase; 2: leucine amino peptidase; 3, γ-glutamyl cysteine synthetase; 4: glutathione synthetase. “a” and “b” refer to glutathione and Cys-Gly transporters, respectively. The connection of the cycle with trans-sulfuration pathway (5: cystathionine γ-lyase) and the effect of possible modulators of the cycle are also reported. SB: serine /borate; PPG: propargylglycine; BSO: butionilsulfoximine. Inhibition or activation effects are indicated by “- “ or “+,” respectively. Dashed lines refer to the proposed effects on extralenticular GSSG accumulation exerted by exogenous GSH, Cys-Gly or/and its disulfide derivatives (OX_Cys-Gly) as emerged from our results.