Cleaves the gamma-glutamyl bond of extracellular glutathione (gamma-Glu-Cys-Gly), glutathione conjugates (such as maresin conjugate (13R)-S-glutathionyl-(14S)-hydroxy-(4Z,7Z,9E,11E,16Z,19Z)-docosahexaenoate, MCTR1) and other gamma-glutamyl compounds (such as leukotriene C4, LTC4) (PubMed:17924658, PubMed:21447318, PubMed:27791009). The metabolism of glutathione by GGT1 releases free glutamate and the dipeptide cysteinyl-glycine, which is hydrolyzed to cysteine and glycine by dipeptidases (PubMed:27791009). In the presence of high concentrations of dipeptides and some amino acids, can also catalyze a transpeptidation reaction, transferring the gamma-glutamyl moiety to an acceptor amino acid to form a new gamma-glutamyl compound (PubMed:17924658, PubMed:7673200, PubMed:7759490, PubMed:8095045, PubMed:8827453, PubMed:21447318). Contributes to cysteine homeostasis, glutathione homeostasis and in the conversion of the leukotriene LTC4 to LTD4. Seems to be inactive. an alpha-amino acid + an N-terminal (5-L-glutamyl)-[peptide] = 5-L-glutamyl amino acid + N-terminal L-alpha-aminoacyl-[peptide] glutathione + H2O = L-cysteinylglycine + L-glutamate an S-substituted glutathione + H2O = an S-substituted L-cysteinylglycine + L-glutamate H2O + leukotriene C4 = L-glutamate + leukotriene D4 (13R)-S-glutathionyl-(14S)-hydroxy-(4Z,7Z,9E,11E,16Z,19Z)-docosahexaenoate + H2O = (13R)-S-cysteinylglycyl-(14S)-hydroxy-(4Z,7Z,9E,11E,16Z,19Z)-docosahexaenoate + L-glutamate Activated by autocatalytic cleavage (PubMed:23682772). Inhibited by serine-borate (PubMed:21447318). Lipid metabolism; leukotriene D4 biosynthesis. Sulfur metabolism; glutathione metabolism. Heterodimer composed of the light and heavy chains. The active site is located in the light chain. Detected in fetal and adult kidney and liver, adult pancreas, stomach, intestine, placenta and lung. There are several other tissue-specific forms that arise from alternative promoter usage but that produce the same protein. Lung-specific. N-glycosylated on both chains. Contains hexoses, hexosamines and sialic acid residues. Glycosylation profiles tested in kidney and liver tissues reveal the presence of tissue-specific and site-specific glycan composition, despite the overlap in composition among the N-glycans. A total of 36 glycan compositions, with 40 unique structures are observed. Up to 15 different glycans are observed at a single site, with site-specific variation in glycan composition. The difference in glycosylation profiles in the 2 tissues do not affect the enzyme activity. Cleaved by autocatalysis into a large and a small subunit and the autocatalytic cleavage is essential to the functional activation of the enzyme. The disease is caused by variants affecting the gene represented in this entry. A large homozygous deletion that removes several exons of all isoforms of GGT1 has been found in one family affected by glutathionuria. Cys-454 was thought to bind the gamma-glutamyl moiety, but mutagenesis of this residue had no effect on activity. Chloride ions bound in the active site cavity may contribute to stabilize the protein fold. Produced by alternative promoter usage. Produced by alternative splicing of isoform 1. Produced by alternative promoter usage. Belongs to the gamma-glutamyltransferase family. Extended N-terminus. Gamma-glutamyl transpeptidase entry