Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.5.1.18 (glutathione S-transferase)
 22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Toxic effects of SO2 and sulfite such as bronchitis and bronchoconstriction have been well documented. SO2 has also been suggested to potentiate carcinogenic effects of PAH. However, the molecular basis of these toxic effects is unclear. We have examined the covalent reaction of SO2 and sulfite with cellular proteinacious and nonproteinaceous sulfhydryl compounds using rat liver, and lung and human lung derived A549 cells. Reactions of sulfite and protein in rat and human lung cells reveals at least three proteins with sulfite-reactive disulfide bonds. Besides fibronectin and serum albumin, which had been reported to contain sulfonated products following exposure to sulfite, we have found one other protein with sulfite-binding capabilities. Since the integrity of disulfide bonds is crucial to the tertiary structure and thus protein function, the disruption of protein structure by sulfitolysis may result in altered cellular activities leading to biochemical lesions. Using carefully controlled conditions, reproducible GSH contents can be found in cultured cells and used as an experimental basis for studying alterations in the GSH and GSSG content of cells. Sulfitolysis of GSSG results in the formation of GSSO3H in A549 cells, and possibly in the lung. GSSO3H can be reduced enzymatically by GSSG reductase. However, the Km of GSSO3H is high compared to that of GSSG, suggesting the existence of a transient concentration of GSSO3H once it is formed. Cysteine S-sulfonate is, however, not reduced by cytosolic extracts in the presence of NADPH and would have to be eliminated from the cell by other means. GSSO3H is a strong competitive inhibitor of GST in rat liver and lung and A549 cells, using 1-chloro-2,4-dinitrobenzene as a substrate. It also inhibits the formation of GSH conjugates of BP 4,5-oxide, anti and syn BPDE, but to a lesser extent. These results suggest that SO2 may affect the detoxification of xenobiotic compounds by inhibiting, via formation of GSSO3H, the enzymatic conjugation of GSH and reactive electrophiles. Since GSH conjugation represents the major pathway of elimination of BP epoxides in the lung, our results offer a possible explanation for the cocarcinogenicity of SO2 with PAHs. These data suggest that the sulfitolysis reaction of sulfite is the common reaction mechanism mediating the underlying biochemical reactions leading to both the toxic and cocarcinogenic properties of SO2. Quantitation of sulfitolysis products and their interaction with cellular processes should provide a coherent scheme relating SO2 and sulfite toxicity among animal species and humans.
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PMID:Covalent reactions in the toxicity of SO2 and sulfite. 376 76

After rats were injected with the reduced glutathione (GSH) depletor phorone (diisopropylidene acetone, 250 mg/kg, i.p.), there was a significant increase in microsomal glutathione S-transferase activity in the liver. The maximum activity was observed 24 hr after injection and was about 2-fold that of the control activity. Diethylmaleate (500 mg/kg, i.p.) had the same effect. Twenty-four hours after phorone injection (250 mg/kg, i.p.), the concentrations of GSH and oxidized glutathione (GSSG) in the liver were increased about 2-fold. Under the same conditions, the level of mixed disulfides with microsomal proteins (GSS-protein) was also increased. Further, the activity of microsomal glutathione S-transferases was increased by the in vitro addition of disulfide compounds such as GSSG, cystine and homocystine, and the activity increased by GSSG was reduced to control levels by incubating with the corresponding sulfhydryl compounds such as GSH, cysteine and homocysteine respectively. Thus, microsomal glutathione S-transferase activity appears to be regulated by the formation and/or cleavage of a mixed disulfide bond between the sulfhydryl group present in the enzyme and GSSG. Therefore, the increase of microsomal glutathione S-transferase activity after phorone injection may be due to the formation of a mixed disulfide bond between the sulfhydryl group in the enzyme and GSSG.
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PMID:Possible regulation mechanism of microsomal glutathione S-transferase activity in rat liver. 394 80

A comparative study of the effect of misonidazole and novel radiosensitizers on glutathione (GSH) levels and related enzyme activities in isolated rat hepatocytes was performed. Incubation of hepatocytes with 5 mM radiosensitizers led to a decrease in the intracellular GSH level. The most pronounced decrease in cellular GSH was evoked by 2,4-dinitroimidazole-1-ethanol (DNIE); after incubation for only 15 min, GSH was hardly detected. DNIE-mediated GSH loss was dependent upon its concentration. DNIE reacted with GSH nonenzymatically as well as with diethylmaleate, while misonidazole and 1-methyl-2-methyl-sulfinyl-5-methoxycarbonylimidazole (KIH-3) did not. Addition of partially purified glutathione S-transferase (GST) did not enhance DNIE-mediated GSH loss in a cell-free system. DNIE inhibited glutathione peroxidase (GSH-Px), GST, and glutathione reductase (GSSG-R) activities in hepatocytes, while misonidazole and KIH-3 did not. GSH-Px activity assayed with H2O2 as substrate was the most inhibited. Inhibition of GSH-Px activity assayed with cumene hydroperoxide as substrate and GST was less than that of GSH-Px assayed with H2O2 as substrate. GSSG-R activity was decreased by DNIE, but not significantly. Incubation of purified GSH-Px with DNIE resulted in a little change in the activity when assayed with H2O2 as substrate.
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PMID:Effect of hypoxic cell radiosensitizers on glutathione level and related enzyme activities in isolated rat hepatocytes. 402 32

Glutathione-depleted hepatocytes, by incubation with diethylmaleate (DEM) or phorone (2,6-dimethyl-2,5-heptadiene-4-one), i.e., substrates of the GSH S-transferases (EC 2.5.1.18), showed rates of gluconeogenesis from various precursors significantly lower than controls; however the rate of glucose synthesis from fructose was similar to that of controls. Isolated hepatocytes from rats pretreated with those substrates 1 h before isolation to deplete hepatic glutathione (GSH) also showed a decrease of the rate of gluconeogenesis from lactate plus pyruvate. Incubation of hepatocytes with L-buthionine sulfoximine, a specific inhibitor of gamma-glutamyl-cysteine synthetase (EC 6.3.2.2), resulted in a decreased rate of gluconeogenesis from lactate plus pyruvate only when GSH values were lower than 1 mumol/g cells. Freeze-clamped livers from GSH-depleted rats showed a higher concentration of malate and glycerol 3-phosphate, indicating that GSH depletion probably affects phosphoenolpyruvate carboxykinase and glycerol-3-phosphate dehydrogenase activities. Several indicators of cell viability, such as lactate dehydrogenase leakage, malondialdehyde accumulation, ATP concentration, or urea synthesis from different precursors, were not affected by GSH depletion under the experimental conditions used here. Besides, the GSH/GSSG ratio remained unchanged in all cases.
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PMID:Effects of glutathione depletion on gluconeogenesis in isolated hepatocytes. 402 24

1. The name ;glutathione S-aralkyltransferase' is proposed for the enzyme catalysing the reaction of benzyl chloride with GSH. 2. Results from heat-inactivation studies, ammonium sulphate-fractionation and acid-precipitation experiments, and studies of the distribution of activities in rat liver, in rat kidney and in the livers of other animals indicate that glutathione S-aralkyltransferase differs from glutathione S-alkyltransferase, S-aryltransferase, S-epoxidetransferase and an S-alkenetransferase. 3. The distribution of these enzymes in the livers of the animal species examined was different. 4. Glutathione S-alkyltransferase, S-aralkyltransferase and the S-alkenetransferase that are present in rat liver supernatant were inhibited by GSSG, and the nature of the inhibition varied in each case. 5. 3,5-Di-tert.-butyl-4-hydroxybenzyl acetate reacts spontaneously with GSH, but the rat liver-supernatant-catalysed reaction of GSH with this and other aralkyl esters was weak. 6. A probable function of the glutathione S-transferases is the protection of cellular constituents from strong electrophilic agents.
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PMID:Glutathione S-aralkyltransferase. 536 Jul 27

1-Chloro-2,4-dinitrobenzene (CDNB) was used to conjugate glutathione (GSH) through the catalysis of lens glutathione S-transferase without the untoward oxidative damage to the lens mediated by GSH oxidants. A 2 hr treatment of the rat lens with 1 mM CDNB resulted in a nearly total depletion of lens GSH with neither formation of GSSG nor glutathione-protein mixed disulfides. Rubidium uptake was found to decrease linearly with the loss of GSH; nevertheless, ionic imbalance did not commence until more than 30% cation pump activity was lost. Glycolytic rate dropped following CDNB treatment, due probably to a decline in demand for ATP by the deactivated cation pump. 31P-NMR studies confirmed the irreversible loss of ATP. CDNB depletion of GSH resulted in a two-fold increase in 14CO2 production from [14C]-1-glucose. Whereas oxidative stress resulted in a six-fold increase in glucose utilization through the hexose monophosphate shunt (HMPS), CDNB-treated lenses showed no such stimulation. This indicated that the residual GSH following CDNB treatment was insufficient for the activation of the glutathione peroxidase-reductase-HMPS mechanism and raised the possibility that the increased glucose utilization might be due to mechanisms other than the HMPS. These results indicate an intimate correlation between the GSH content and major metabolic functions in the lens.
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PMID:Effect of glutathione deprivation on lens metabolism. 609 26

Total glutathione (GSH and GSSG) level, and the activities of gamma-glutamylcysteine synthetase, gamma-glutamyltranspeptidase (gamma-GTP), glutathione S-transferase (GST), glutathione peroxidase (GSH-Px) and glutathione reductase (GR) in the liver were investigated in rats, mice, guinea pigs and hamsters. Hepatic GSH level in rats, mice, guinea pigs and hamsters were 7.1, 7.8, 3.5 and 5.4 mM, respectively. The lower level of GSH in guinea pigs seems to be in part attributed to the higher activity of hepatic gamma-GTP, an enzyme which catalyzes GSH breakdown. Moreover, a marked species difference in the activities of GST, GSH-Px and GR was also observed. A 48 h-fasting resulted in a decrease of GSH and GSSG levels in rats, mice and guinea pigs, but not in hamsters. In addition, both nicotineamide adenine dinucleotide phosphate- and ascorbate-dependent lipid peroxidation produced by 9000 X g supernatant fraction in fasted animal species occurred most highly in the rat followed by hamster and guinea pig, and almost undetectable in mice. Thus, it suggests that the occurrence of lipid peroxidation in fasted animals may not be related to the hepatic GSH level, and rather, a lack of occurrence of lipid peroxidation in fasted mice may be due to the increased activity of GSH-Px activity.
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PMID:Species difference in glutathione level and glutathione related enzyme activities in rats, mice, guinea pigs and hamsters. 614 91

A modification of a specific assay for the reduced (GSH) and oxidized (GSSG) species of glutathione is presented and compared with the method of Ellman (1959). The present method has an enzymatic basis using GSH as the specific cosubstrate for glutathione S-transferase activity. The enzymatic method resulted in comparable, but consistently lower, values for GSH and GSSG than did the method of Ellman. The greatest differences between the two methods occurred when measuring renal GSH and GSSG, possibly due to the presence of mixed thiols in the kidney. This enzymatic method was more specific and provided an accurate and reproducible method of GSH and GSSG determination.
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PMID:Direct enzymatic assay for reduced and oxidized glutathione. 653 23

Previous studies [Kondo, T., Dale, G. L. and Beutler, E. (1981) Biochim. Biophys. Acta, 645, 132-136] have shown evidence for the existence of two different active-transport processes for glutathione disulphide (GSSG) in human erythrocytes (the high-Km and low-Km processes). In the present investigation adenosine-triphosphate-dependent transport of glutathione S-conjugate was characterized in comparison with active glutathione transport using inside-out vesicles from human erythrocytes. Incubation of the vesicles with glutathione S-conjugate (S-2,4-dinitrophenylglutathione) was found to inhibit competitively the high-Km process of GSSG transport but not significantly affect the low-Km process. The glutathione S-conjugate transport required ATP. A lineweaver-Burk plot of the transport rate as a function of the conjugate concentration gave an apparent Km value of 0.94 mM. The Km value of ATP-Mg was 0.76 mM. The transport of glutathione S-conjugate was dependent on temperature. Preincubation of vesicles with dithiothreitol resulted in an increase of the transport rate while thiol reagents, such as iodoacetamide, N-ethylmaleimide and p-chloromercuribenzoate inhibited the transport. Addition of nucleotides, such as CTP, UTP or GTP had no effect on the transport. These findings suggest that glutathione S-conjugate formed by the catalytic reaction of glutathione S-transferase in erythrocytes under the exposure to electrophilic compounds, is eliminated via the same transport process for GSSG elevated under oxidative stress.
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PMID:Glutathione S-conjugate transport using inside-out vesicles from human erythrocytes. 711 53

Rat liver glutathione S-transferases (RX: glutathione R-transferase, EC 2.5.1.18) were found to adsorb S-carbamidomethyl glutathione linked to Sepharose CL-4B via lysyl or aliphatic diamine spacers of various carbon chain lengths (-NH-(CH2)n-NH-, n = 2, 4, 5, 6, 8 and 10). Proteins were eluted specifically by reduced glutathione. The affinity of the enzymes for the adsorbent increased with increase in the carbon chain length of aliphatic diamine spacers used. Adsorbent having a free carboxyl group within the spacer moiety had high capacity and was specific for glutathione S-transferases. The transferases were specifically eluted from the column in high yield by low concentrations of glutathione. Enzymes purified by the lysyl spacer adsorbent were homogeneous in sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and contained most of the hepatic glutathione S-transferase isozymes in isoelectric focusing. Oxidized glutathione and S-methyl glutathione were equally effective as reduced glutathione in eluting glutathione S-transferases from the adsorbent, but gamma-glutamylcysteinylglycineamide or gamma-glutamylcysteinylglycine-1-methyl ester were not effective. These data suggested that the free carboxyl group of glycyl moiety of glutathione might also be important for the specific binding of the transferases to this adsorbent.
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PMID:Affinity chromatography of hepatic glutathione S-transferases on omega-aminoalkyl sepharose derivatives of glutathione. 726 99


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