Gamma-Glutamylcyclotransferase (gGCT)

GGCT (EC 2.3.2.4) catalyzes the formation of 5-oxoproline (pyroglutamic acid) from gamma-glutamyl dipeptides and may play a significant role in glutathione homeostasis.The deduced 188-amino acid protein has a calculated molecular mass of 21 kD. EST database analysis revealed moderate GGCT expression in a wide range of human tissues, with highest levels in bladder and salivary gland. Database analysis identified GGCT orthologs in a range of species from C. elegans to mammals, but not in plants.GGO-induced apoptosis was inhibited by a dominant-negative mutation of JNK (MAPK8) that impeded JNK signaling, suggesting involvement of JNK and CRF21 in GGO-induced apoptosis.The enzymatic kinetics were similar to those of GGCT purified from human erythrocytes.