InterPro domain: IPR036568

Gamma-glutamyl cyclotransferase (GGCT) catalyzes the formation of pyroglutamic acid (5-oxoproline) from dipeptides containing gamma-glutamyl, and is a dimeric protein. In Homo sapiens, the protein is encoded by the gene C7orf24 [ 1 ]. The enzyme participates in the gamma-glutamyl cycle, which plays a pre-eminent role in glutathione homoeostasis [ 2 ]. The synthesis and metabolism of glutathione (L-gamma-glutamyl-L-cysteinylglycine) ties the gamma-glutamyl cycle to numerous cellular processes; glutathione acts as a ubiquitous reducing agent in reductive mechanisms involved in protein and DNA synthesis, transport processes, enzyme activity, and metabolism.

Structurally, GGCT is comprised of 7 beta strands and 2 alpha helices, and it folds into a five-stranded, antiparallel beta-barrel [ 3 ].

1. The identification and structural characterization of C7orf24 as gamma-glutamyl cyclotransferase. An essential enzyme in the gamma-glutamyl cycle. J. Biol. Chem. 283, 22031-42
2. Glutathione. Annu. Rev. Biochem. 52, 711-60
3. Crystal structure of a conserved hypothetical protein (gi: 13879369) from Mouse at 1.90 A resolution reveals a new fold. Proteins 61, 1132-6