Glutathione-specific gamma-glutamylcyclotransferases 1 and 2 (CHAC1 and 2) catalyse the specific cleavage of glutathione (GSH) into 5-oxoproline (OPRO) and a cysteinylglycine (CysGly) dipeptide. GSH acts a redox buffer in cells and its depletion is an important factor for apoptosis, oxidative stress and progression of cancer. CHAC1 and 2 act as proapototic agents with implications for human health and disease (Mungrue et al. 2009, Crawford et al. 2015).