Biomaterial Database

Active deglycosylated mammalian gamma-glutamyl transpeptidase. 1994

T K Smith, and A Meister

Department of Biochemistry, Cornell University Medical College, New York, New York 10021.

gamma-Glutamyl transpeptidase, a highly glycosylated heterodimeric enzyme that is usually attached to the external surface of cell membranes, is of major importance in the metabolism of glutathione. The enzyme, which has been isolated from many animal sources, contains a large amount of carbohydrate, which is linked to both protein subunits. Previous work has not shown whether such carbohydrate is needed for enzyme activity nor indicated its functional role. Notably, gamma-glutamyl transpeptidase isolated from Escherichia coli, which exhibits about 80% amino acid sequence homology with the rat enzyme, has only about 0.1% of its specific enzymatic activity and is not glycosylated. Here we treated the highly glycosylated gamma-glutamyl transpeptidases isolated from rat and pig kidneys with a mixture of glycosidases and then separated two completely active gamma-glutamyl transpeptidase fractions from each species. One fraction was completely devoid of carbohydrate and was fully active as compared with the respective isolated enzymes, but differed in solubility and stability. The other fraction, which contained 10-20% of the initially bound carbohydrate, exhibited a marked increase in susceptibility to proteases. The oligosaccharide chains of gamma-glutamyl transpeptidase may protect against protease action (including self-destruction by the inherent protease activity of the light subunit) during synthesis of the active enzyme from its single chain precursor, as well as after enzyme synthesis.

UI	MeSH Term	Description	Entries
D007668	Kidney	Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.	Kidneys
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D010446	Peptide Fragments	Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.	Peptide Fragment,Fragment, Peptide,Fragments, Peptide
D002241	Carbohydrates	A class of organic compounds composed of carbon, hydrogen, and oxygen in a ratio of Cn(H2O)n. The largest class of organic compounds, including STARCH; GLYCOGEN; CELLULOSE; POLYSACCHARIDES; and simple MONOSACCHARIDES.	Carbohydrate
D004355	Drug Stability	The chemical and physical integrity of a pharmaceutical product.	Drug Shelf Life,Drugs Shelf Lives,Shelf Life, Drugs,Drug Stabilities,Drugs Shelf Life,Drugs Shelf Live,Life, Drugs Shelf,Shelf Life, Drug,Shelf Live, Drugs,Shelf Lives, Drugs
D004591	Electrophoresis, Polyacrylamide Gel	Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.	Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D005723	gamma-Glutamyltransferase	An enzyme, sometimes called GGT, with a key role in the synthesis and degradation of GLUTATHIONE; (GSH, a tripeptide that protects cells from many toxins). It catalyzes the transfer of the gamma-glutamyl moiety to an acceptor amino acid.	GGTP,Glutamyl Transpeptidase,gammaglutamyltransferase,gamma-Glutamyl Transpeptidase,Transpeptidase, Glutamyl,Transpeptidase, gamma-Glutamyl,gamma Glutamyl Transpeptidase,gamma Glutamyltransferase
D006026	Glycoside Hydrolases	Any member of the class of enzymes that catalyze the cleavage of the glycosidic linkage of glycosides and the addition of water to the resulting molecules.	Endoglycosidase,Exoglycosidase,Glycohydrolase,Glycosidase,Glycosidases,Glycoside Hydrolase,Endoglycosidases,Exoglycosidases,Glycohydrolases,Hydrolase, Glycoside,Hydrolases, Glycoside
D006031	Glycosylation	The synthetic chemistry reaction or enzymatic reaction of adding carbohydrate or glycosyl groups. GLYCOSYLTRANSFERASES carry out the enzymatic glycosylation reactions. The spontaneous, non-enzymatic attachment of reducing sugars to free amino groups in proteins, lipids, or nucleic acids is called GLYCATION (see MAILLARD REACTION).	Protein Glycosylation,Glycosylation, Protein
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations