Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

1. Two lithocholic acid-binding proteins in rat liver cytosol, previously shown to have glutathione S-transferase activity, were resolved by CM-Sephadex chromatography. 2. Phenobarbitone administration resulted in induction of both binding proteins. 3. The two proteins had distinct subunit compositions indicating that they are dimers with mol.wts. 44 000 and 47 000. 4. The two lithocholic acid-binding proteins were identified by comparing their elution volumes from CM-Sephadex with those of purified ligandin and glutathione S-transferase B prepared by published procedures. Ligandin and glutathione S-transferase B were eluted separately, as single peaks of enzyme activity, at volumes equivalent to the two lithocholic acid-binding proteins. 5. Peptide 'mapping' revealed structural differences between the two proteins.
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PMID:Identification of two lithocholic acid-binding proteins. Separation of ligandin from glutathione S-transferase B. 51 49

After the intravenous injection of unconjugated [(3)H]bilirubin into normal Sprague-Dawley and Wistar R rats, radiolabeled bile pigments rapidly accumulated in the liver. By 1.5 min after injection, an average of 36% of the injected isotope was present in liver homogenates. Between 3 and 15 min, 37-64% of the total intrahepatic radiolabeled bilirubin was conjugated, as demonstrated by extraction of label into the polar phase of a solvent partition system. This indicates both rapid conjugation, and accumulation of conjugated bilirubin within the liver cell. Fluorometric determination of the dissociation constants of purified bilirubin and its mono- and diglucuronides for homogeneous preparations of two human and four rat glutathione S-transferases, including ligandin, revealed avid binding of all three bile pigments to this class of proteins. Hence, the observation that the intrahepatic bile pigment pool contains substantial amounts of conjugated bilirubin can be attributed to the high binding affinities observed. Thin-layer chromatographic analysis of the (3)H-pigments produced by p-iodoaniline diazotization of homogenates and cytosol demonstrated that the intrahepatic pool of conjugated bilirubin was almost exclusively monoglucuronide. Examination of radiolabeled bilirubin conjugates excreted in bile during the first 20 min after injection of [(3)H]bilirubin showed no preferential excretion of diglucuronide. These studies indicate that (a) both bilirubin and its monoglucuronide accumulate within the liver cell as ligands with the glutathione S-transferase; and (b) bilirubin diglucuronide does not significantly accumulate within the general intrahepatocellular pool of protein-bound bile pigments. The latter observation is compatible with the formation and excretion of bilirubin diglucuronide directly from the canalicular pool of the liver cell.
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PMID:Hepatic accumulation and intracellular binding of conjugated bilirubin. 61 9

The effects of inhalation and cutaneous exposure to styrene on the drug metabolizing enzymes were studied in the rat. Rats were exposed eight hours per day, for seven successive days to 450 ppm concentration of styrene or received one cutaneous dose of styrene daily for seven consecutive days (0.5 and 3.0 g/kg). The animals were killed one day after the last dose. Styrene inhalation increased the activities of epoxide hydrase and UDPglucuronosyltransferase (4-methylumbelliferone as substrate) in liver (1.5- and 1.7-fold, respectively). Ethoxycoumarin deethylation was enhanced 1.7-fold in the kidney. The content of cytochrome P-450 in the liver and the activities of NADPH cytochrome c-reductase, benzpyrene hydroxylase and glutathione S-transferase in the liver and kidney were not altered. No changes in the enzyme activities were detected in the lung. Styrene depressed the epoxide hydrase activity in liver when administered cutaneously. No signs of enzyme induction could be seen after cutaneous administration.
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PMID:Effects of inhalation and cutaneous exposure to styrene on drug metabolizing enzymes in the rat. 62 79

There are two enzymes in rat liver with glutathione peroxidase activity when cumene hydroperoxide is used as substrate. One is the selenium-requiring glutathione peroxidase (glutathione:hydrogen-peroxide oxidoreductase, EC 1.11.1.9) and the other appears to be independent of dietary selenium. Activities of the two enzymes vary greatly among tissues and among animals. The molecular weight of the enzyme with selenium-independent glutathione peroxidase activity was estimated by gel filtration to be 35 000, and the subunit molecular weight was estimated by dodecyl sulfate-polyacrylamide gel electrophoresis to be 17 000. Double reciprocal plots of enzyme activity as a function of substrate concentration produced intersecting lines which are suggestive of a sequential reaction mechanism. The Km for glutathione was 0.20 mM and the Km for cumene hydroperoxide was 0.57 mM. The enzyme was inhibited by N-ethylmaleimide, but not by iodoacetic acid. Inhibition by cyanide was competitive with respect to glutathione and the Ki for cyanide was 0.95 mM. This selenium-independent glutathione peroxidase also catalyzes the conjugation of glutathione to 1-chloro-2,4-dinitrobenzene. Along with other similarities to glutathione S-transferase, this suggests that the selenium-independent glutathione peroxidase and glutathione S-transferase activities in rat liver are of the same enzyme.
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PMID:Glutathione peroxidase activities from rat liver. 62 91

Spectrophotometric and equilibrium-dialysis measurements show that ligandin (glutathione S-transferase B, EC 2.5.1.18) binds monomeric porphyrins at a single site with association constants in the range 10(4)-10(6) litre/mol at pH 7.0. Binding affinities are paralleled by the tendencies of the porphyrins to aggregate, increasing in the order: uroporphyrins I and III less than coproporphyrins I and III approximately haematoporphyrin less than protoporphyrin IX. From this it is deduced that the hydrophobic effect is the predominant driving-force for binding. The porphyrins can be displaced from their binding site on ligandin by bromosulphophthalein and oestrone sulphate. In enzyme inhibition studies, 50% inhibition was brought about by 8 micron-haematoporphyrin and by 1 micron-protoporphyrin IX. In the analysis of the haemotoporphyrin-ligandin system the self-association of haematoporphyrin was studied in detail. It was found to be limited to dimerization in the concentration range 0-200 micron at pH 7.0, 25 degrees C and a dimerization constant of 1.9 x 10(5) litre/mol was determined. Coproporphrin III has a dimerization constant of 5.2 x 10(5) litre/mol under the same conditions.
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PMID:The binding of porphyrins by ligandin. 64 88

Recent work had indicated the presence of a non selenium-dependent glutathione peroxidase activity in rat liver in addition to the selenium-dependent activity. The present study was undertaken to learn whether the glutathione S-transferases are reponsible for the non selenium-dependent glutathione peroxidase activity and to study the effect of selenium deficiency on those enzymes. Glutathione S-transferase B was purified by an established method using carboxymethyl cellulose ion exchange chromatography and studied. It exhibited glutathione peroxidase activity toward cumene hydroperoxide and t-butyl hydroperoxide. A limiting Km of 0.55 mM was determined for cumene hydroperoxide. Sulfobromophthalein was found to be a competitive inhibitor with respect to cumene hydroperoxide of the glutathione peroxidase activity of glutathione S-transferase B. Selenium deficiency caused an increase in glutathione S-transferase activity. These results establish that glutathione S-transferase B contributes to the non selenium-dependent glutathione peroxidase activity in rat liver and show that it increases in selenium deficiency when the selenium-dependent glutathione peroxidase is decreased.
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PMID:Hepatic cytosolic non selenium-dependent glutathione peroxidase activity: its nature and the effect of selenium deficiency. 65 Mar

The administration of trans-stilbene oxide to rats resulted in increased hepatic microsomal and nuclear epoxide hydrase (with styrene oxide (SO), benzo[a]pyrene 4,5-oxide (4,5-BP) as substrates) and aryl hydrocarbon hydroxylase (AHH) activities. Hepatic microsomal aminopyrine N-demethylase, benzphetamine N-demethylase, and ethylmorphine N-demethylase activities were also increased. These increases in microsomal enzyme activity were dose- and time-dependent (about 100% at 200 mg/kg body weight, administered for 2 consecutive days). However, only marginal increases in hepatic microsomal NADPH-cytochrome c reductase activity and cytochrome P-450 content were observed. No apparent proliferation of hepatic endoplasmic reticulum occurred in trans-stilbene oxide pretreated rats. The administration of trans-stilbene oxide has no effect on hepatic glutathione S-transferase activities (with SO or 4,5-BPO as substrates). None of the parameters were affected in pulmonary microsomes from treated rats. The in vitro addition of trans-stilbene oxide (10(-6)--10(-2) M) did not affect hepatic epoxide hydrase or glutathione S-transferase activities.
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PMID:trans-Stilbene oxide: an inducer of rat hepatic microsomal and nuclear epoxide hydrase and mixed-function oxidase activities. 69 68

Rats and mice were exposed to the fumes of oxidative thermal degradation of polystyrene (350 degrees C). A decrease in the reduced glutathione (GSH) in both liver and lung was detected immediately after both the acute (mice, 3 h) and subacute (rats, 3 weeks) exposures were stopped. Later on an elevation in the amount of GSH due to the increased synthesis (rebound effect) could be seen. Cytochrome P-450 content in mouse liver was initially decreased after acute exposure, but the prolonged treatment doubled the amount of the P-450 hemoprotein in liver microsomes. After acute exposure 7-ethoxycoumarin 9-deethylase activity in mouse liver was doubled in 24 h. When the exposures were continued, this enhancement in ethoxycoumarin O-deethylase activity gradually disappeared. O-deethylase activity was also enhanced in rat liver and lung after subacute exposure. The exposures given had no effect on diphenyloxazole hydroxylase, and the effects on the conjugating enzymes (epoxide hydratase, UDPglucuronosyltransferase, glutathione S-transferase)) were insignificant in rat liver.
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PMID:Effects of thermal degradation products of polystyrene on drug biotransformation and tissue glutathione in rat and mouse. 73 18

Levels of glutathione, glutathione reductase and glutathione S-transferase activities in rat lung and liver have been investigated. After perfusing the lung to remove contaminating blood, this organ was found to have an apparent concentration of glutathione (2mM) which is approx. 20% of that found in the liver. Both organs contain very low levels of glutathione disulfide. Neither phenobarbital nor methylcholanthrene had a significant effect on the levels of reduced glutathione in lung and liver. In addition, the activities of some glutathione-metabolizing enzymes--glutathione reductase and glutathione S-transferase activity assayed with four different substrates--were observed to be 5-to 60-fold lower in lung tissue than in the liver.
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PMID:Levels of glutathione, glutathione reductase and glutathione S-transferase activities in rat lung and liver. 76 Aug 19

The glutathione S-transferases are a group of proteins with overlapping substrate specificities and ligand-binding capacities. This report examines certain approaches to the measurement of transferase B (ligandin) in the rat liver. The ratio of catalytic activities toward 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene gives some indication of the relative proportions of the various transferases present in 100 000 g supernatants. The fraction of catalytic activity towards 1-chloro-2,4-dinitrobenzene, due to transferase B, was best measured by immunoprecipitation with anti-(transferase B). Male rat liver exhibited three times more activity towards 1,2-dichloro-4-nitrobenzene than female tissue; however, the activities towards 1-chloro-2,4-dinitrobenzene were almost identical. By assuming a specific activity of 11 mumol/min per mg, immunoprecipitable transferase B comprised 4.5 +/- 0.2% of total protein in the 100 000 g supernatant of female rat liver, and 70% of the transferase activity towards 1-chloro-2,4-dinitrobenzene. The amount of transferase B in the 100 000 g supernatant from male rat liver is significantly lower with respect to both fraction of total protein (3.3 +/- 0.2%) and overall transferase activity towards 1-chloro-2,4-dinitrobenzene (48%). Hypophysectomy eliminated this sex difference in the hepatic concentration of glutathione S-transferase B.
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PMID:A sex difference in hepatic glutathione S-transferase B and the effect of hypophysectomy. 82 87


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