Figure 6.

Glutathione biosynthesis and function: (A) Cysteine and glutamate are enzymatically linked to γ-glutamylcysteine via the action of glutamate cysteine ligase (GCL). The next step in synthesis is the formation of glutathione itself from cysteine and γ-glutamylcysteine via glutathione synthetase (GS). (B) Glutathione can be oxidized to glutathione dimers (GSSG) and thereby serves to buffer oxidants within the cell. A shift in the equilibrium from GSH towards a higher proportion of GSSG may promote the glutathiolation of free cysteines on protein surfaces, thus shielding these cysteine residues during oxidative stress conditions from over-oxidation. Illustration was redrawn from [116].