Role of Glutathione in Cancer Progression and Chemoresistance

Figure 2

γ-Glutamyl cycle. In the γ-glutamyl cycle, GSH is released from the cell and the ectoenzyme GGT transfers the γ-glutamyl moiety of GSH to an amino acid (aa, the best acceptor being cysteine), forming γ-glutamyl-aa and cysteinyl-glycine. The γ-glutamyl-amino acid can then be transported back into the cell and once inside can be further metabolized to release the aa and 5-oxoproline, which can be converted to glutamate and used for GSH synthesis. Cysteinyl-glycine is broken down by dipeptidase (DP) to generate cysteine ​ ​and glycine. Once inside the cell, the majority of cysteine is incorporated into GSH, some being incorporated into protein, and some degraded into sulfate and taurine [18].