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)

Thirteen forms of glutathione S-transferase were isolated from human liver in high yields by glutathione-affinity chromatography and chromatofocusing. Apparent isoelectric points ranged from 4.9 to 8.9 and included neutral forms. All 13 forms appeared to be identical immunochemically in a quantitative enzyme-linked immunosorbent assay. These forms were immunochemically distinct from the major acidic glutathione S-transferase found in placenta and erythrocyte and were immunochemically distinct from two forms of higher molecular weight glutathione S-transferase found in some but not all liver samples. The 13 forms exhibited similar activities with 1-chloro-2,4-dinitro-benzene as substrate, specific activities of 33-94 mumol/min/mg. Likewise, these forms all exhibited glutathione peroxidase activity with cumene hydroperoxide, specific activities of 1.5-8.3 mumol/min/mg. All 13 forms bound bilirubin with subsequent conformational changes leading to states devoid of transferase activity, a process prevented by the presence of foreign proteins. As hematin-binding proteins, however, these multiple transferases exhibited a very broad range of binding extending from nonbinding to high-affinity binding (KD approximately 10(-8) M). Hematin binding was noncompetitive with transferase activity and did not involve the bilirubin-binding site, suggesting the existence of unique heme-binding sites on these proteins. The two forms of the immunochemically distinct glutathione S-transferases transferases found in some liver samples also exhibited both transferase and peroxidase activities. In addition, they also have separate sites for binding bilirubin and hematin.
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PMID:Isolation and characterization of the multiple glutathione S-transferases from human liver. Evidence for unique heme-binding sites. 404 71

The effects of the xenobiotics, i.e. butylated hydroxytoluene, beta-naphthoflavone, isosafrole, pregnenolone-16 alpha-carbonitrile, trans-stilbene oxide, 3-methylcholanthrene, phenobarbital, 3,3',4,4'-tetrachlorobiphenyl, 2,2',4,4',5,5'-hexachlorobiphenyl, on rat liver cytosolic glutathione transferase and glutathione peroxidase activities have been investigated. Although the glutathione transferase isozymes (measured by the specific substrates ethacrynic acid and delta 5-androstene-3,17-dione) which have been shown to possess peroxidase activity were significantly increased, little or no increase in peroxidase activity (toward cumene hydroperoxide, tert-butyl hydroperoxide or hydrogen peroxide) was observed. Likewise during a 16-day time course following the administration of Aroclor 1254 or fireMaster BP-6 (each 500 mg/kg, i.p.), potent induction of glutathione transferase activities was seen without any significant increases in peroxidase activities. In fact during the second week of the time course, there were significant decreases in selenium-dependent glutathione peroxidase activity (toward hydrogen peroxide). The inverse regulation of these activities, i.e. the depression of selenium-dependent glutathione peroxidase activity following sustained induction of glutathione transferases, may have direct implications for the toxicity of the polyhalogenated aromatic hydrocarbons.
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PMID:Differential regulation of hepatic glutathione transferase and glutathione peroxidase activities in the rat. 405 12

Duplicate groups of rainbow trout (Salmo gairdneri) (mean weight 11 g) were given for 40 weeks one of four partially purified diets that were either adequate or low in selenium or vitamin E or both. Weight gains of trout given the dually deficient diet were significantly lower than those of trout given a complete diet or a diet deficient in Se. No mortalities occurred and the only pathology seen was exudative diathesis in the dually deficient trout. There was significant interaction between the two nutrients both with respect to packed cell volume and to malondialdehyde formation in the in vitro NADPH-dependent microsomal lipid peroxidation system. Tissue levels of vitamin E and Se decreased to very low levels in trout given diets lacking these nutrients. For plasma there was a significant effect of dietary vitamin E on Se concentration. Glutathione (GSH) peroxidase (EC 1.11.1.9) activity in liver and plasma was significantly lower in trout receiving low dietary Se but was independent of vitamin E intake. The ratios of hepatic GSH peroxidase activity measured with cumene hydroperoxide and hydrogen peroxide were the same for all treatments. This confirms the absence of a Se-independent GSH peroxidase activity in trout liver. Se deficiency did not lead to any compensatory increase in hepatic GSH transferase (EC 2.5.1.18) activity; values were essentially the same in all treatments. Plasma pyruvate kinase (EC 2.7.1.40) activity increased significantly in the trout deficient in both nutrients. This was thought to be due to leakage of the enzyme from the muscle and may be indicative of incipient (subclinical) muscle damage.
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PMID:Some effects of vitamin E and selenium deprivation on tissue enzyme levels and indices of tissue peroxidation in rainbow trout (Salmo gairdneri). 406 58

A comparative study of reduced glutathione (GSH) concentrations and activities of GSH related-enzymes in urinary bladder transitional epithelium (UBTE), urinary bladder nontransitional tissue (UBNT), and liver of the rabbit, was carried out to investigate the reasons for the susceptibility of UBTE towards peroxidase-mediated chemical carcinogenesis. Cooxidative activation of chemical carcinogens by prostaglandin H synthase occurs at high levels in UBTE and minimally in UBNT. Other peroxidases are also likely to activate carcinogenic xenobiotics in the urinary bladder. GSH concentrations in UBTE and UBNT were low compared to that in the liver. gamma-Glutamyl transpeptidase activities were much lower in UBTE and in UBNT than those in the liver. Activities of selenium-dependent and selenium-independent glutathione peroxidases were very low in UBTE and UBNT. Cytosolic glutathione S-transferase activity towards 1,2-epoxy-(4-nitrophenoxy)propane was very low in UBTE. Microsomal glutathione S-transferase activity towards 1-chloro-2,4-dinitrobenzene was much lower in UBTE than in the liver. We propose that the low GSH concentration and diminished activities of glutathione peroxidases, gamma-glutamyl transpeptidase, and certain isozymes of glutathione S-transferase could be responsible for the vulnerability of UBTE towards chemical carcinogenesis.
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PMID:Low activities of glutathione-related enzymes as factors in the genesis of urinary bladder cancer. 614 17

Antibodies raised against rat hepatic epoxide hydrolase (EC 3.3.2.3) and glutathione S-transferases (EC 2.5.1.18) B, C and E were used to determine the presence and localizations of these epoxide-metabolizing enzymes in testes of sexually immature and mature Wistar and Holtzman rats. Unlabeled antibody peroxidase-antiperoxidase staining for each enzyme was readily detected in rat testes at the light microscopic level. Although significant strain-related differences were not apparent, staining intensity for certain enzymes differed markedly between Leydig cells and seminiferous tubules. Leydig cells of immature and mature rats were stained much more intensely for epoxide hydrolase and glutathione S-transferases B and E than were seminiferous tubules, whereas Sertoli cells, spermatogonia, spermatocytes and spermatids, as well as Leydig cells, were stained intensely by the anti-glutathione S-transferase C. Age-related differences in staining for glutathione S-transferase B were not obvious, while the anti-glutathione S-transferase C stained seminiferous tubules more intensely in immature rats, and antibodies to epoxide hydrolase and glutathione S-transferases C and E stained Leydig cells much more intensely in mature rats. These observations thus demonstrate that testes of both sexually immature and mature rats contain epoxide hydrolase and glutathione S-transferases. Except for glutathione S-transferase C in immature rats, Leydig cells appear to contain much higher levels of enzymes than do seminiferous tubules. During sexual maturation, the testicular level of glutathione S-transferase B appears to remain constant, while levels of epoxide hydrolase and glutathione S-transferases C and E increase within Leydig cells and the level of glutathione S-transferase C decreases within seminiferous tubules.
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PMID:Localization of epoxide-metabolizing enzymes in rat testis. 638 44

A low Se intake in dietetically treated patients with phenylketonuria (PKU) or maple syrup urine disease (MSUD) leads to a marked reduction of the platelet glutathione peroxidase activity (GSHPx). The mean value amounted to 2.0 U/10(11) platelets with t-butyl hydroperoxidase (t-BOOH) (2.2 U/10(11) with H2O2) in patients and 5.8 U/10(11) with t-BOOH (5.4 U/10(11) with H2O2) in the control children. After Se supplementation with yeast rich in Se (dose: 135 micrograms Se/m2) the GSHPx activities rapidly increased. They reached a plateau after 2-3 weeks and remained there during the following 15-20 weeks of supplementation. After the cessation of supplementation there was a slow decrease, the values reached a low plateau after 24 weeks. In addition platelet glutathione S-transferase (GSHTf) was estimated with 1-chloro-2,4-dinitrobenzene. No significant difference between the values in healthy and dietetically treated patients in a low or normal Se state was observed. GSHTf did not exhibit peroxidase activity and did not show a compensatory increase when Se dependent GSHPx activity was low. The patients do not reveal clinical signs of disturbed platelet function. GSHPx may act in platelets via lipoxygenase on the prostaglandin pathway. The physiologic consequence of altered arachidonate metabolism, when GSHPx is deficient in platelets, remains to be elucidated.
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PMID:Glutathione peroxidase and glutathione S-transferase activity of platelets. 662 46

The glutathione S-transferases (EC 2.5.1.18) have been purified to electrophoretic homogeneity from 105,000g supernatant of sheep liver homogenate by employing a combination of gel filtration on Sephadex G-150 and affinity chromatography on S-hexylglutathione-linked Sepharose-6B columns. Approximately 70% of the original glutathione S-transferase activity toward 1-chloro-2,4-dinitrobenzene and glutathione peroxidase activity toward cumene hydroperoxide could be recovered by this purification method. Of particular importance in developing this procedure was the fact that the enzyme preparation obtained after affinity column chromatography represented all the isozymes of sheep liver glutathione S-transferases. Further purification by CM-cellulose and DEAE-cellulose column chromatography resolved the glutathione S-transferases into seven distinct cationic isozymes designated C-1, C-2, C-3, C-4, C-5, C-6, and C-7 and five overlapping anionic transferases designated A-1, A-2, A-3, A-4, and A-5, respectively, in the order of their elution from the ion-exchange columns. The sodium dodecyl sulfate SDS-gel electrophoretic data on subunit composition revealed that cationic enzymes are composed of two subunits with an identical Mr of 24,000 whereas a predominant subunit with Mr of 26,000 was observed in all anionic isozyme peaks except A-1. Cationic isozymes accounted for approximately 98% of the total peroxidase activity associated with the glutathione S-transferase whereas only A-1 of the anionic isozymes displayed some peroxidase activity. Isozyme C-4 was found to be the most abundant glutathione S-transferase in the sheep liver. Characterization of the individual transferases by their specificity toward a number of selected substrates, subunit composition, and isoelectric points showed some similarities to those patterns for human liver glutathione S-transferases.
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PMID:Purification and characterization of the individual glutathione S-transferases from sheep liver. 687 Feb 66

We have purified five forms of glutathione S-transferase from rat liver. One form was the glutathione S-transferase B (ligandin), which is composed of two non-identical subunits with molecular weights of 22,000 (Ya) and 25,000 (Yc). Two of the other transferases were Ya and Yc homodimers. The other two transferases were also homodimers, but their subunit, Yb, had a molecular weight of 24,000. The three proteins containing either Ya or Yc subunits had similar substrate specificities, and all three contained peroxidase activity. The greatest peroxidase activity was present in proteins containing the Yc subunit. Enzymes composed of Yb subunits had minimal peroxidase activity in addition to different substrate specificities. The Ya and Yc containing enzymes bound the ligands bilirubin, and indocyanine green with high affinity (KD less than 5 microM), although the KD values of the YcYc protein were consistently 4- to 12-fold greater than those of the other two transferases. Studies were performed to define the origins of the various isozymes. There was no evidence for conversion of Yc to either Ya or Yb during storage or under conditions favorable to proteolysis. Hybridization studies were performed under denaturing conditions (6 M guanidine-HCl), and a YaYc hybrid was formed from the YaYa and YcYc proteins. In addition, both YaYa and YcYc hybrids were formed from transferase B. The hybrids were functionally similar to the proteins isolated originally from the liver. Attempts to form a YaYb hybrid from the YbYb and YaYa transferases were unsuccessful. This result is consistent with the lack of this enzyme form in the liver. Glutathione S-transferase B and the Ya and Yc homodimers appeared to be hybrids of common subunits. These three transferases had very similar functional and structural characteristics and differed from the transferases that are composed of Yb subunits.
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PMID:Structural, functional and hybridization studies of the glutathione S-transferases of rat liver. 688 61

We have purified two isoenzymes of glutathione S-transferase from bovine retina to apparent homogeneity through a combination of gel-filtration chromatography, affinity chromatography and isoelectric focusing. The more anionic (pI = 6.34) and less anionic (pI = 6.87) isoenzymes were comparable with respect to kinetic and structural parameters. The Km for both substrates, reduced glutathione and 1-chloro-2,4-dinitrobenzene, bilirubin inhibition of glutathione conjugation to 1-chloro-2,4-dinitrobenzene, 1-chloro-2,4-dinitrobenzene inactivation of enzyme activity and molecular weight were similar. However, pH optimum and energy of activation were found to differ considerably. Retina was found to have no selenium-dependent glutathione peroxidase activity. The total glutathione peroxidase activity fractionated with the transferases in the gel-filtration range of mol.wt. 49000 and expressed activity with only organic hydroperoxides as substrate. Only the more anionic isoenzyme expressed both transferase and peroxidase activity.
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PMID:Glutathione S-transferases of the bovine retina. Evidence that glutathione peroxidase activity is the result of glutathione S-transferase. 712 77

Sheep antibodies raised against three isoenzymes of glutathione S-transferase (EC 2.5.1.18), transferases B, C, and E, which were isolated and purified to apparent homogeneity from rat liver, have been employed to localize these enzymes at the light microscopic level within livers of untreated rats. Using these antibodies in an unlabeled antibody peroxidase-antiperoxidase staining technique, each glutathione S-transferase was detected immunohistochemically within parenchymal cells throughout the liver lobule. In addition, immunohistochemical staining for transferases C and E, but not for transferase B, was observed within bile duct epithelium. While all parenchymal cells were stained with each glutathione S-transferase antibody, the patterns of immunohistochemical staining intensity observed across the liver lobule with the three anti-transferases were not uniform: parenchymal cells within the centrilobular region were more intensely stained for each lobular region were more intensely stained for each isoenzyme than were those within the midzonal and periportal regions of the lobule. The results of this immunohistochemical study thus demonstrate that glutathione S-transferases are not distributed uniformly throughout the liver lobule and that each transferase is present in the greatest concentration within the centrilobular region of the lobule.
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PMID:Immunohistochemical localization of glutathione S-transferases in livers of untreated rats. 717 91


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