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gamma-glutamyltransferase-1 (GGT1, gamma-glutamyltranspeptidase-1, CD224 antigen)
Function:
- initiates extracellular glutathione (GSH) breakdown
- provides cells with a local cysteine supply
- contributes to maintain intracelular GSH level
- part of cell antioxidant defense mechanism
- catalyzes transfer of glutamyl moiety of glutathione to amino acids & dipeptide acceptors
- alternatively, glutathione can be hydrolyzed to give cys-gly & gamma glutamate (reversible)
- isoform 3 seems to be inactive
- sulfur metabolism; glutathione metabolism
(5-L-glutamyl)-peptide + an amino acid
peptide + 5-L-glutamyl amino acid
Structure:
- heterodimer composed of the light & heavy chains
- the active site is located in the light chain
- belongs to the gamma-glutamyltransferase family
- contains hexoses, hexosamines & sialic acid residues
- not known if the sialic acid residues are present on N-linked glycans or on O-linked glycans
- N-glycosylated on both chains
Compartment: membrane
Alternative splicing:
- named isoforms=3
- alternative promoter usage
Expression:
- detected in fetal & adult kidney & liver, adult pancreas, stomach, intestine, placenta & lung
- isoform 3 is lung-specific
- several other tissue-specific forms that arise from alternative promoter usage but that produce the same protein
Pathology:
- defects in GGT1 are a cause of glutathionuria
Note:
- Cys-454 was thought to bind the gamma-glutamyl moiety, but mutagenesis of this residue had no effect on activity
General
cluster-of-differentiation antigen; cluster designation antigen; CD antigen
gamma-glutamyltransferase (GGT) or gamma-glutamyltranspeptidase
glycoprotein
Properties
SIZE: entity length = 569 aa
MW = 61 kD
COMPARTMENT: cellular membrane
MOTIF: transmembrane domain {5-26}
N-glycosylation site {N95}
N-glycosylation site {N120}
N-glycosylation site {N230}
N-glycosylation site {N266}
N-glycosylation site {N297}
N-glycosylation site {N344}
N-glycosylation site {N511}
Database Correlations
OMIM 231950
UniProt P19440
Pfam PF01019
KEGG correlations
ENZYME 2.3.2.2
References
- UniProt :accession P19440
- Wikipedia, gamma-glutamyl transpeptidase entry
http://en.wikipedia.org/wiki/gamma_glutamyl_transpeptidase