Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glutathione (GSH) binding sites found in brain white matter in a previous study using biotinylated GSH (Third IBRO World Congress Neurosci. Abstr., 1991, P59.17) suggested that there might GSH receptors on glial cells. In the present study, radioligand receptor assays were performed on cultured astrocytes using [35S]GSH. Scatchard analyses of saturation binding of [35S]GSH revealed two binding sites: Kd1 = 2.0 +/- 0.1 nM, Bmax1 = 89.5 +/- 1.5 fmole/2.2 x 10(5) cells and Kd2 = 12.8 +/- 0.4 nM, Bmax2 = 187.7 +/- 2.4 fmol/2.2 x 10(5) cells. The saturable and displacible high affinity [35S]GSH binding we have observed suggests that this binding is not due to GSH sequestration by uptake sites or to the association of GSH with GSH S-transferases or GSH peroxidases which have Kds in the microM range. Colloidal gold and immunofluorescence double labelling were used to visualize the binding sites at the cellular level. Positive colloidal gold decoration further suggests that these labelled binding sites are membrane receptors on astrocytes.
Brain Res Mol Brain Res 1992 Oct
PMID:Characterization and localization of glutathione binding sites on cultured astrocytes. 133 77

Site-directed substitution mutations were introduced into a cDNA expression vector (pUC120 pi) that encoded a human glutathione S-transferase pi isozyme to non-conservatively replace four residues (Tyr7, Arg13, Gln62 and Asp96). Our earlier X-ray crystallographic analysis implicated these residues in binding and/or chemically activating the substrate glutathione. Each substitution mutation decreased the specific activity of the enzyme to less than 2% of the wild-type. Glutathione-binding was also reduced; however, the Tyr7----Phe mutant still retained 27% of the wild-type capacity to bind glutathione, underlining the primary role that this residue is likely to play in chemically activating the glutathione molecule during catalysis.
J Mol Biol 1992 Jul 20
PMID:Mutational substitution of residues implicated by crystal structure in binding the substrate glutathione to human glutathione S-transferase pi. 164 Apr 52

Freshly isolated adult rat heart myocytes contain total glutathione and reduced glutathione (GSH) at levels quite comparable to those in intact rat heart. Total glutathione can be depleted from 11 to 1 nmol/mg protein or less by treatment with cyclohex-2-ene-1-one without effect on either cellular ATP, rod-cell morphology or the integrity of the sarcolemma. Glutathione levels and redox state are not altered significantly when the Ca-tolerant, quiescent cells are subjected to a period of anoxia followed by reoxygenation. This oxygen paradox protocol results in irreversible hypercontracture of the contractile elements into an amorphous mass in the bulk of the cells, but little loss of sarcolemmal integrity. When the myocytes are subjected to an externally applied oxidant stress by the addition of either diamide or t-butylhydroperoxide, GSH is rapidly depleted with accumulation of oxidized glutathione (GSSG. On continued aerobic incubation both of these reagents promote a slower depletion of cellular ATP and a parallel hypercontracture. Cells treated with t-butylhydroperoxide, but not those with diamide, also generate increasing amounts of thiobarbituric acid reactive species as an indication of lipid peroxidation and show a parallel loss of sarcolemmal integrity. It is concluded that respiring myocytes and those subjected to the oxygen paradox do not produce oxygen radicals in sufficient amounts to displace the GSH/GSSG redox poise and depletion of myocyte glutathione per se is not detrimental to the short term survival of the cells. In addition, aerobic myocytes subjected to external oxidant stress can be damaged irreversibly by two pathways, a hypercontracture that correlates with depletion of ATP and a loss of sarcolemmal integrity that correlates with lipid peroxidation.
J Mol Cell Cardiol 1990 May
PMID:Cellular glutathione and the response of adult rat heart myocytes to oxidant stress. 238 82

Certain toxic effects of phenytoin are thought to result from its cytochrome P-450-catalyzed bioactivation to a reactive arene oxide intermediate that binds covalently to proteins. Using an in vitro system, we examined an alternative hypothesis based upon the cooxidation of phenytoin to a reactive free radical intermediate by prostaglandin synthetase (PGS), horseradish peroxidase, or thyroid peroxidase. Microsomes from hepatic, thyroid, seminal vesicular, or pulmonary tissues, or PGS or horseradish peroxidase, were incubated with the appropriate enzymatic cofactors to study activities of cytochromes P-450 (NADPH), PGS (arachidonic acid), thyroid peroxidase (guiaicol, H2O2), and horseradish peroxidase (H2O2). The production of potentially teratogenic, reactive phenytoin intermediates during in vitro incubations was estimated by the amount of radiolabeled phenytoin bound covalently to microsomal protein or bovine serum albumin and by the detection of a free radical intermediate using ESR spectrometry. Arachidonic acid-dependent bioactivation of phenytoin was demonstrated for purified PGS and ram seminal vesicles (RSV), as well as for liver, lung, and kidney. Optimal arachidonate concentrations varied substantially for different tissues. Arachidonate-dependent binding of phenytoin with PGS and RSV was reduced to baseline levels by coincubation with the cyclooxygenase inhibitor indomethacin. Hydrogen peroxide-dependent covalent binding of phenytoin was observed with thyroid peroxidase and horseradish peroxidase, and binding was significantly reduced in these systems and in PGS and RSV by coincubation with the peroxidase inhibitor methimazole. Glutathione, the antioxidants caffeic acid and butylated hydroxyanisole, and the free radical trapping agent alpha-phenyl-N-t-butylnitrone (PBN) all significantly reduced arachidonate-dependent phenytoin binding. Oxygen uptake was increased in a dose-dependent manner by the arachidonate-dependent bioactivation of phenytoin by PGS. ESR spin-trapping techniques using PBN indicated the generation of a free radical intermediate during the metabolism of phenytoin by PGS. These results suggest that the hydroperoxidase component of PGS, as well as thyroid peroxidase and other peroxidases, can bioactivate phenytoin to a reactive free radical intermediate, which may be toxicologically relevant.
Mol Pharmacol 1989 Apr
PMID:In vitro bioactivation of phenytoin to a reactive free radical intermediate by prostaglandin synthetase, horseradish peroxidase, and thyroid peroxidase. 253 58

Glutathione (GSH) transferase isoenzymes have been partially resolved from the cytosol of Schistocephalus solidus (plerocercoid) by GSH affinity chromatography and chromatofocusing at pH 7-5. The presence of isomeric forms was also suggested by analytical isoelectric focusing and high-performance liquid chromatography (HPLC). Gel filtration and sodium dodecyl sulphate-polyacrylamide gel electrophoresis indicated that GSH transferase forms were dimers with a subunit size of approximately 24 kDa. The major GSH transferase form in S. solidus (plerocercoid) showed greater biochemical relationship to the Mu family of mammalian GSH transferase compared to the mammalian Alpha or Pi families. The major subunit purified by GSH affinity chromatography and reversed-phase HPLC also showed high N-terminal homology with the Mu family. A minor GSH transferase form appeared more biochemically related to the Alpha family with respect to substrate specificity and inhibitor sensitivity. The major GSH transferase was inhibited by haematin-related compounds, bile acids and a number of anthelmintics including members of the benzimidazole and phenol-based class of compounds. The major GSH transferase had conjugating activity with members of the trans, trans-2,4-alkadienal and trans-2-alkenal series, secondary products of lipid peroxidation.
Mol Biochem Parasitol 1989 Sep
PMID:Purification of cytosolic glutathione transferases from Schistocephalus solidus (plerocercoid): interaction with anthelmintics and products of lipid peroxidation. 277 Jul 89

The hepatotoxicity of N-acetyl-p-aminophenol (acetaminophen, paracetamol) was investigated in hepatocyte cultures obtained from eight different human liver biopsies. Incubation of hepatocytes with paracetamol resulted in a dose- and time-dependent glutathione depletion. Glutathione decreased linearly for 8 h, reaching a minimum after 12 h of exposure. Cytotoxicity, assessed as loss of cellular protein from plates, was observed only when glutathione decreased below 20% for more than 12 h. However, in one donor, cytotoxicity was observed with even a moderate glutathione decrease. Prestimulation of hepatocytes with 1 mM phenobarbital or 2 microM methylcholanthrene for 48 h did not lead to a significant increase of paracetamol toxicity, although the glutathione levels in 3-methylcholanthrene-treated cells were somewhat lower. Several metabolic precursors were examined in vitro for their ability to increase intracellular glutathione and the results showed the following sequence: N-acetylcysteine greater than thioproline greater than cysteine greater than 2-oxo-4-thiazolidine carboxylic acid greater than methionine. However, only N-acetylcysteine, thioproline, and cysteine substantially increased glutathione levels when 1 mM paracetamol was present in the incubation medium and thus prevented its toxicity. N-acetylcysteine elevated glutathione even after 24 h of preexposure to paracetamol. The fact that cell damage did not correlate with glutathione levels in all human cultures suggests that glutathione depletion may not be the only determinant of paracetamol toxicity in human hepatocytes.
Mol Toxicol
PMID:Toxicity of paracetamol in human hepatocytes. Comparison of the protective effects of sulfhydryl compounds acting as glutathione precursors. 350 88

We have investigated the role of glutathione in determining the macromolecular binding and cytotoxicity of cisplatin (DDP) and melphalan (LPAM) in human ovarian carcinoma cells and DDP-resistant L1210 mouse leukemia cells. Glutathione reacted avidly with DDP in normal saline with a bimolecular rate constant of 16.2 M-1 hr-1. Glutathione had no effect on the rate of hydrolysis of LPAM, consistent with the SN1-like reaction mechanism of LPAM. Glutathione protected calf thymus DNA and bovine serum albumin from DDP platination and LPAM alkylation. Glutathione also protected nuclei isolated from human ovarian carcinoma cells from DDP platination. The importance of intracellular glutathione in determining the cytotoxicity of DDP and LPAM was assessed by depletion of glutathione with buthionine sulfoximine in three cell types. Exposure to 0.5 mM buthionine sulfoximine for 20-28 hr depleted glutathione to levels that were 10-20% of control levels. COLO 316 and 2008 human ovarian carcinoma cells, and ZCR9 mouse leukemia cells were all sensitized to LPAM cytotoxicity by this level of glutathione depletion. The dose modification factors, defined as the IC50 control cells/IC50 depleted cells, were: 2.6 +/- 0.5 for COLO 316 cells, 1.6 +/- 0.1 for 2008 cells, and 2.1 +/- 1.1 for ZCR9 cells. In contrast, glutathione depletion had a minimal effect on DDP cytotoxicity in these cells with dose modification factors of: 1.2 +/- 0.2 for COLO 316 cells, 0.8 +/- 0.3 for 2008 cells, and 1.1 +/- 0.1 for ZCR9 cells. The differential potentiation of DDP and LPAM cytotoxicity by glutathione depletion in these cells, despite the similar protection that glutathione affords macromolecules from drug binding, suggests that there are fundamental differences in the intracellular interaction of these electrophilic drugs with glutathione.
Mol Pharmacol 1986 Dec
PMID:Differential sensitization of human ovarian carcinoma and mouse L1210 cells to cisplatin and melphalan by glutathione depletion. 378 41

The possible role of oxygen free radicals in the development of reperfusion arrhythmias was investigated using a 10-min period of coronary ligation followed by reperfusion in the isolated rat heart. Superoxide dismutase (5 to 20 u/ml) glutathione (10(-5) to 10(3)M) and ascorbic acid (10(-4) to 5 X 10(-4) M) when given before coronary ligation attenuated the development of reperfusion arrhythmias. Mannitol (2 X 10(-2)M) and catalase (100 and 300 u/ml) did not have any significant effect on reperfusion arrhythmias when given alone but they did potentiate the antiarrhythmic effect of superoxide dismutase. Glutathione, and a combination of superoxide dismutase, catalase and mannitol also reduced the incidence of reperfusion induced ventricular fibrillation when given just before reperfusion. By perfusing hearts with ferricytochrome C it was possible to show an increased reduction of ferricytochrome C during the first minute of reperfusion which could be prevented by the addition of superoxide dismutase. These results provide evidence that oxygen free radicals are produced and may be important in the genesis of reperfusion induced arrhythmias in the isolated rat heart.
J Mol Cell Cardiol 1985 May
PMID:Effect of some free radical scavengers on reperfusion induced arrhythmias in the isolated rat heart. 392 98

The effects of the administration of tryptophan and/or cysteine on carbon tetrachloride (CCl4)-induced hepatic injury were investigated. Rats received CCl4 (1 ml/kg ip) followed 6 hr later by tryptophan (300 mg/kg) and/or cysteine (950 mg/kg) via stomach tube and rats were killed after 24 hr. Treatment with tryptophan, cysteine, or both reduced the degree of hepatic necrosis observed histologically. While CCl4 caused polyribosomal disaggregation and decreased [14C]leucine incorporation into liver proteins in vitro and in vivo, treatment with tryptophan, cysteine, or both caused a shift in polyribosomes toward heavier aggregation and protein synthesis was increased. Serum activities of lactic dehydrogenase (LDH), glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, and gamma-glutamyl-transpeptidase were markedly increased after CCl4 alone but after subsequent treatment with cysteine or with tryptophan and cysteine appreciable decreases occurred. Glutathione concentration decreased but total amount remained constant in the livers of CCl4-treated rats while subsequent treatment with cysteine alone or together with tryptophan elevated both levels of glutathione. Using isolated hepatocytes, CCl4 caused decreases in cell viability, in release of LDH, and in [14C]leucine incorporation into protein. Treatment with CCl4 and tryptophan and/or cysteine revealed that cysteine alone or with tryptophan improved cell viability and decreased LDH release of the cells, while tryptophan alone or with cysteine improved protein synthesis. Upon cytologic evaluation, the isolated hepatocytes revealed membrane distortions after CCl4 alone but these were less marked after CCl4 plus tryptophan, cysteine, or both (most improvement). Thus, tryptophan and cysteine act in a beneficial manner against CCl4-induced hepatic injury in the rat.
Exp Mol Pathol 1985 Dec
PMID:Protective effect of tryptophan and cysteine against carbon tetrachloride-induced liver injury. 406 14

We have previously shown that the bleomycin-induced autooxidation of ferrous iron follows Michaelis--Menten kinetics which are characteristic of enzymatic reactions [Caspary, W. J., Lanzo, D. A., Niziak, C., Friedman, R., & Bachur, N. R. (1979) Mol. Pharmacol. 16, 256]. In this paper, we identify the iron complexes formed during this reaction. The first is a ferrous iron--bleomycin complex which can be considered the catalyst substrate complex. The product of this reaction is a ferric iron--bleomycin complex which is found in a low-spin and a high-spin form. The relative concentrations of these two forms are a function of pH. Glutathione, a biologically relevant reducing agent, binds to the ferric iron--bleomycin complex, reduces it, and may serve as a model for the reduction of the ferric iron--bleomycin complex to the ferrous state during the catalytic cycle. Oxygen uptake induced by bleomycin and ferrous iron is not inhibited by superoxide dismutase (SOD) or catalase. In the absence of bleomycin, catalase strongly inhibits oxygen uptake. This suggests the presence of a relatively stable intermediate in which the superoxide radical is not readily accessible to superoxide dismutase. At pH 9.3, we are able to observe a transient species by electron spin resonance (ESR). When potassium superoxide is added to the ferric iron--bleomycin complex, the same ESR spectrum is produced. We suggest that a transient species composed of a ferric iron, the superoxide ion, and bleomycin is formed. The precise nature of the binding cannot be determined from the data presented.
 ...
PMID:Intermediates in the ferrous oxidase cycle of bleomycin. 616 82


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