Mammalian proapoptotic factor ChaC1 and its homologues function as γ-glutamyl cyclotransferases acting specifically on glutathione.

ChaC1 is a mammalian proapoptic protein of unknown function induced during endoplasmic reticulum stress. We show using in vivo studies and novel in vitro assays that the ChaC family of proteins function as γ-glutamyl cyclotransferases acting specifically to degrade glutathione but not other γ-glutamyl peptides. The overexpression of these proteins (but not the catalytically dead E>Q mutants) led to glutathione depletion and enhanced apoptosis in yeast. The ChaC family is conversed across all phyla and represents a new pathway for glutathione degradation in living cells, and the first cytosolic pathway for glutathione degradation in mammalian cells.