GGCT belongs to the gamma-glutamylcyclotransferase family. It catalyzes the formation of 5-oxoproline from gamma-glutamyl dipeptides, the penultimate step in glutathione catabolism. GGCT may play a significant role in glutathione homeostasis. GGCT also induces release of cytochrome c from mitochondria with resultant induction of apoptosis. Pseudogenes of GGCT gene are located on the long arm of chromosome 5 and the short arm of chromosomes 2 and 2. Alternatively spliced transcript variants encoding multiple isoforms have been observed for this gene.