The cell's recyclable antioxidant
Glutathione is a tripeptide of glutamate, cysteine, and glycine, with cysteine providing the reactive thiol group. In its reduced form (GSH) it neutralizes reactive oxygen species. Glutathione peroxidase (GPx) uses GSH to reduce hydrogen peroxide and lipid peroxides to water and alcohols, and in doing so GSH is oxidized to its disulfide form, GSSG.
Regeneration powered by NADPH
To keep working, the cell must regenerate GSH from GSSG. Glutathione reductase (GR) performs this step using NADPH as the electron source, much of which comes from the pentose phosphate pathway. The ratio of GSH to GSSG is a common indicator of a cell's redox state. While glutathione is central to antioxidant defense, oral glutathione supplements are poorly absorbed and the evidence that they raise tissue levels or treat disease is limited. General educational information, not medical advice.