Glutathione depleting drugs, antioxidants and intestinal calcium absorption

Figure 1 Intestinal glutathione metabolism. The γ-glutamyl cycle comprises the enzymatic reactions involved in the extracellular glutathione (GSH) degradation and the intracellular GSH synthesis: The enzymes γ-glutamyl transpeptidase and dipeptidase, localized in plasma membrane of enterocytes, cleave the extracellular GSH to their constituent amino acids. Within the enterocytes the GSH is synthesized de novo by two reactions that consume adenosine triphosphate that are catalyzed by glutamate cysteine ligase and glutathione synthetase, sequentially. In the redox couple that ensures the maintenance of the cellular redox state participates the enzymes glutathione peroxidase and glutathione reductase. GSH: Glutathione; GSSG: Glutathione disulfide; GGT: γ-glutamyl transpeptidase; GCL: Glutamate cysteine ligase; GS: Glutathione synthetase; GR: Glutathione reductase; GPX: Glutathione peroxidase; DP: Dipeptidase.