Localization of γ‐glutamyl transpeptidase in lymphoid cells

Marathe, Gopal V.; Damle, Nitin; Haschemeyer, Rudy H.; Tate, Suresh S.

doi:10.1016/0014-5793(80)81185-9

Cited by 20 publications

(2 citation statements)

References 11 publications

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“…GGT has been detected both in blood and bone marrow cells by using cytochemical methods (Szmigielski et al, 1965). It has been demonstrated at the ultrastructural level on the surface membrane and membranes of endoplasmic reticulum and golgi apparatus of human lymphoid cells (Marathe et al, 1980). Girino et al (1985) have demonstrated the existence of the enzyme in almost all normal leukocytes and in platelets at cytochemical level.…”

Section: Introductionmentioning

confidence: 99%

Activity Determination, Kinetic Analyses and Isoenzyme Identification of Gamma Glutamyltransferase in Human Neutrophils

Şener¹,

Yardımcı²

2005

BMB Reports

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Gamma-glutamyltransferase (GGT, EC 2.3.2.2) which hydrolyzes glutathione (GSH), is required for the maintenance of normal intracellular GSH concentration. GGT is a membrane enzyme present in leukocytes and platelets. Its activity has also been observed in human neutrophils. In this study, GGT was purified from Triton X-100 solubilized neutrophils and its kinetic parameters were determined. For kinetic analyses of transpeptidation reaction, γ-glutamyl p-nitroanilide was used as the substrate and glycylglycine as the acceptor. Apparent K m values were determined as 1.8 mM for γ-glutamyl pnitroanilide and 16.9 mM for glycylglycine. The optimum pH of GGT activity was 8.2 and the optimum temperature was 37ºC. It had thermal stability with 58% relative activity at 56ºC for 30 min incubation. L-serine, in the presence of borate, was detected as the competetive inhibitor. Bromcresol green inhibited neutrophil GGT activity as a noncompetetive inhibitor. The neutrophils seem to contain only the isoenzyme that is present in platelets. We characterized the kinetic properties and compared the type of the isoenzyme of neutrophil GGT with platelet GGT via polyacrylamide gel electrophoresis (PAGE) under a standart set of conditions.

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Section: Introductionmentioning

confidence: 99%

Activity Determination, Kinetic Analyses and Isoenzyme Identification of Gamma Glutamyltransferase in Human Neutrophils

Şener¹,

Yardımcı²

2005

BMB Reports

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“…Other experiments by Novodgrosky et al (57) with lymphoid cells and by Inoue et al (38) with ascites tumor cells also support this conclusion. More recently, studies with antibodies to human 7-glutamyltranspeptidase have shown that the enzyme is localized on the cell surface of lymphoid cells while ultrastructure studies with a histochemical substrate also revealed transpeptidase activity in the Golgi and endo plasmic reticulum (46). This latter localization was attributed to the processing pathway of newly synthesized enzyme.…”

Section: Extracellular Degradation Of Glutathionementioning

confidence: 94%

Characterization and Physiological Function of Rat Renal γ-Glutamyltranspeptidase

Curthoys

Hughey²

1979

Enzyme

135

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Rat renal γ-glutamyltranspeptidase is an intrinsic membrane glycoprotein. The larger of its two subunits is apparently folded into two distinguishable domains which are separated by a protease-sensitive sequence of amino acids. Membrane binding of γ-glutamyltranspeptidase results from the hydrophobic interaction of the nonpolar domain of the amphipathic subunit with the lipid bilayer. Localization of at least a portion of the γ-glutamyl binding site on the smaller subunit limits the active site of the enzyme to one side of the membrane. Within the kidney, the enzyme is primarily associated with the luminal surface of the brush border membrane of the proximal straight tubule. Comparison of the kinetic properties of γ-glutamyltranspeptidase with the pH and the substrates available within the tubular fluid suggests that the physiologically significant reaction catalyzed by the transpeptidase is the hydrolysis of glutathione and its S-derivatives. The glutathionemia and glutathionuria observed in a patient who lacks detectable γ-glutamyltranspeptidase activity and in mice following specific inhibition of transpeptidase, support the hypothesis that the enzyme plays a major role in glutathione catabolism. It now appears that the activities attributed to the γ-glutamyl cycle do not participate in amino acid transport, but instead constitute three separate metabolic pathways; the intracellular synthesis of glutathione, the intracellular degradation of γ-glutamyl peptides and the extracellular hydrolysis of glutathione. The finding that various cells release reduced and oxidized glutathione indicates that glutathione turnover may be a process of intracellular synthesis, excretion and extracellular degradation.

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Enzyme analysis and subcellular fractionation of human peripheral blood lymphocytes with special reference to the localization of putative plasma membrane enzymes

Shah

Webster

1983

Cell Biochemistry & Function

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Human lymphocytes were isolated from defibrinated blood by Ficoll-Hypaque centrifugation with erythrocyte hypotonic lysis. Homogenates of mixed lymphocytes were subjected to analytical subcellular fractionation by sucrose gradient centrifugation in a Beaufay automatic zonal rotor. The principal organelles were characterized by their marker enzymes: cytosol (lactate dehydrogenase), plasma membrane (5'-nucleotidase), endoplasmic reticulum (neutral alpha-glucosidase), mitochondria (malate dehydrogenase), lysosomes (N-acetyl-beta-glucosaminidase), peroxisomes (catalase). gamma-Glutamyl transferase was exclusively localized to the plasma membrane. Leucine amino-peptidase, especially when assayed in the presence of Co2+, was also partially localized to the plasma membrane. Experiments with diazotized sulphanilic acid, a non-permeant enzyme inhibitor, showed that these plasma membrane enzymes are present on the cell surface. No detectable alkaline phosphatase was found in the lymphocytes. Acid phosphatase and beta-glucuronidase were localized to lysosomes and there was some evidence for lysosomal heterogeneity. Leucine amino peptidase, optimal at pH 8.0, showed a partial localization to intracellular vesicles, possibly lysosomes, especially when assayed in the presence of EDTA. These studies provide a technique for determining the intracellular distribution of hitherto unassigned lymphocyte constituents and serve as a basis for investigating the cell pathology of lymphocytic disorders.

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Localization of γ‐glutamyl transpeptidase in lymphoid cells

Cited by 20 publications

References 11 publications

Activity Determination, Kinetic Analyses and Isoenzyme Identification of Gamma Glutamyltransferase in Human Neutrophils

Activity Determination, Kinetic Analyses and Isoenzyme Identification of Gamma Glutamyltransferase in Human Neutrophils

Characterization and Physiological Function of Rat Renal γ-Glutamyltranspeptidase

Enzyme analysis and subcellular fractionation of human peripheral blood lymphocytes with special reference to the localization of putative plasma membrane enzymes

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