GGT1

The enzyme encoded by this gene is a type I gamma-glutamyltransferase that catalyzes the transfer of the glutamyl moiety of glutathione to a variety of amino acids and dipeptide acceptors. The enzyme is composed of a heavy chain and a light chain, which are derived from a single precursor protein. It is expressed in tissues involved in absorption and secretion and may contribute to the etiology of diabetes and other metabolic disorders. Multiple alternatively spliced variants have been identified. There are a number of related genes present on chromosomes 20 and 22, and putative pseudogenes for this gene on chromosomes 2, 13, and 22. [provided by RefSeq, Jan 2014]

Gamma-Glutamyltransferase 1

Cleaves the gamma-glutamyl bond of extracellular glutathione (gamma-Glu-Cys-Gly), glutathione conjugates and other gamma-glutamyl compounds, such as leukotriene C4 (LTC4). The metabolism of glutathione by GGT1 releases free glutamate and the dipeptide cysteinyl-glycine, which is hydrolyzed to cysteine and glycine by dipeptidases. 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.

Isoform 3:
Seems to be inactive.

Cellular amino acid metabolic process Source: UniProtKB
Cysteine biosynthetic process Source: UniProtKB
Fatty acid metabolic process Source: BHF-UCL
Glutamate metabolic process Source: UniProtKB
Glutathione biosynthetic process Source: UniProtKB
Glutathione catabolic process Source: UniProtKB
Leukotriene D4 biosynthetic process Source: BHF-UCL
Leukotriene metabolic process Source: UniProtKB
Peptide modification Source: GO_Central
Proteolysis Source: UniProtKB
Regulation of immune system process Source: UniProtKB
Regulation of inflammatory response Source: UniProtKB
Response to estradiol Source: GO_Central
Response to lipopolysaccharide Source: GO_Central
Response to tumor necrosis factor Source: GO_Central
Spermatogenesis Source: UniProtKB
Zymogen activation Source: UniProtKB

Cell membrane

Glutathionuria (GLUTH):
A very rare, autosomal recessive metabolic disorder characterized by the presence of glutathione in the urine, due to generalized gamma-glutamyl transpeptidase deficiency. Most patients manifest mild to moderate mental retardation, and behavioral disturbance. Seizures, tremor, marfanoid features and strabismus are observed in some patients.

Cytoplasmic: 1-4
Helical: 5-26
Extracellular: 27-569

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.