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

Inhalation of cigarette smoke specifically induces the rat lung and kidney aryl hydrocarbon hydroxylase (AHH) in less than 4 h. The epoxide hydratase (EH) and the glutathione S-transferase are not significantly modified by a similar treatment in any of the rat tissues. Compared to the kidney AHH, the lung hydroxylase is 3--4 times more sensitive to small concentrations of cigarette smoke and seems to have a longer biological half-life. In both tissues, the induced AHH presents the same in vitro sensitivity to various inhibitors as a polycyclic hydrocarbon induced AHH. In primary fetal rat liver cell culture, the cigarette smoke condensate fractions (CSCF) induce both the AHH and EH activity. Nevertheless, the AHH activity responds faster and to lower concentrations of CSCF than the EH activity. The liver cell culture constitutes a unique tool for a comparative study of the AHH and EH induction mechanism. Low concentration (10 muM) of benz(a)anthracene induces only the AHH activity while trans-stilbene oxide enhances selectively the EH activity. Appropriate concentrations of CSCF or of phenobarbital (PB) determine a parallel induction of both enzymes. The results are discussed on the basis of (a) the existence of specific mechanisms of AHH regulation in the lung and in the kidney and (b) the existence of coordinated or independent biochemical control of the AHH and EH activity.
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PMID:Organ specificity of induction of activating and inactivating enzymes by cigarette smoke and cigarette smoke condensate. 28 33

1. Cytosol from trout liver, gills and intestinal caeca has substantial glutathione S-transferase activity. 2. Gel-exclusion and ion-exchange chromatography suggest that trout liver has several glutathione S-transferases with different molecular weights and ionic charges. 3. A component capable of binding lithocholic acid eluted together with glutathione S-transferase activity. Some of the transferase activity did not elute together with binding activity. 4. The enzymic activity from trout liver was less stable at 37 degrees C than that from rat liver. 5. The glutathione S-transferases of fish liver have a similar specific activity to those of rat liver but different molecular properties.
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PMID:A comparison of the glutathione S-transferases of trout and rat liver. 31 20

Activities of epoxide hydrase (EH) and glutathione S-transferase (GST) have been measured in pulmonary tissue from several species. On the basis of total organ activity, pulmonary tissue has less capacity than liver tissue to metabolize epoxides. Pulmonary EH and GST appear to be refractory to induction by typical agents. Rat pulmonary GST will conjugate a variety of epoxides, but K-region epoxides are metabolized at lower rates than alkene oxides. In the isolated perfused rabbit lung, benzo (a) pyrene-4,5-oxide (BPO) is metabolized by EH and GST at similar initial rates, but EH activity is lost after a few minutes, apparently owing to inadequate local substrate levels. GST from rabbit lung cytosol has been separated by chromatographic methods into six peaks of enzymic activity (toward 1-chloro-2,4-denitrobenzene). Of these peaks, all six metabolized BPO and two metabolized styrene oxide. Although EH and GST are less active in lung than in liver, pulmonary metabolism of epoxides is important because this tissue must be able to protect itself from arene oxides generated by pulmonary oxidative metabolism of polycyclic aromatic hydrocarbons.
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PMID:Pulmonary metabolism of epoxides. 35 80

The C3H mouse liver h-protein is a cytoplasmic protein to which metabolites of carcinogenic polycyclic hydrocarbons bind covalently following i.p. injection. It has a number of physical properties similar to those of the glutathione S-transferases (EC 2.5.1.18). These properties include molecular weight (40,000), number of subunits (2), basic isoelectric point around 8.0, sedimentation coefficient (3.5S), and subcellular localization. In this communication, we have shown that glutathione S-transferase activities with 1,2-epoxy(3-p-nitrophenoxy)propane and benz[a]anthracene 5,6-oxide as substrates were separated from the h-protein on carboxymethylcellulose and isoelectrofocusing columns. The purification of the mouse h-protein as a [3H]-7,12-dimethylbenz[a]anthracene conjugate or as the free form is also described.
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PMID:Separation of glutathione S-transferase activities with epoxides from the mouse liver h-protein, a major polycyclic hydrocarbon-binding protein. 41 9

Ligandin (glutathione S-transferase B, EC 2.5.1.18)was treated with p-mercuribenzoate, N-(4-dimethylamino-3,5-dinitrophenyl)-maleimide, 5,5,-dithiobis-(2-nitrobenzoic acid), N-ethylmaleimide, iodoacetamide or iodoacetate. Although performic acid oxidation revealed the presence of four cysteines, p-mercuribenzoate and N-(4-dimethylamino-3,5-dinitrophenyl)maleimide, the most effective of the reagents studied, reacted with only three residues. N-Ethylmaleimide and 5,5'-dithiobis-(2-nitrobenzoic acid) each reacted with two cysteines: iodoacetamide reacted with only one cysteine and iodoacetate was essentially unreactive. Modification of three thiol groups decreased both the enzymic and binding activities of ligandin although the number of binding sites was unaffected. Modification of only one or two of the thiol groups had little effect on the ligandin activities. It therefore appears that there is a thiol group in the common hydrophobic-ligand- and substrate-binding site of ligandin. Ligandin was separated into two fractions on CM-cellulose. Both fractions gave the same results with p-mercuribenzoate and iodoacetamide.
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PMID:The binding and catalytic activities of forms of ligandin after modification of its thiol groups. 43 43

Glutathione derivatives inhibit glutathione S-transferase A [cf. Biochem. J. (1975) 147, 513--522]. The steady-state kinetics of this inhibition have been investigated in detail by using S-octyglutathione, glutathione disulphide and S-(2-chloro-4-nitrophenyl)glutathione: the last compound is a product of the enzyme-catalused reaction. Interpreted in terms of generalized denotations of inhibition patterns, the compounds were found to be competitive with the substrate glutathione. Double-inhibition experiments involving simultaneous use of two inhibitors indicated exclusive binding of the inhibitors to the enzyme. The discrimination between alternative rate equations has been based on the results of weighted non-linear regression analysis. The experimental error was determined by replicate measurements and was found to increase with velocity. The established error structure was used as a basis for weighting in the regression and to construct confidence levels for the judgement of goodness-of-fit of rate equations fitted to experimental data. The results obtained support a steady-state random model for the mechanism of action of glutathione S-transferase A and exclude a number of simple kinetic models.
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PMID:Multiple inhibition of glutathione S-transferase A from rat liver by glutathione derivatives: kinetic analysis supporting a steady-state random sequential mechanism. 44 9

Methadone . HCl given in the drinking water for 4 weeks increased microsomal epoxide hydratase activity in the liver of adult male Wistar rats, with no change in aryl hydrocarbon hydroxylase activity. In contrast, in female rats it raised aryl hydrocarbon hydroxylase with no change in epoxide hydratase activity. Gonadectomy altered the effect of methadone on epoxide hydratase, but not on aryl hydrocarbon hydroxylase activity, in both sexes. In ovariectomized rats, but not in controls, methadone nearly doubled the epoxide hydratase activity, whereas in male rats castration decreased the inductive effect of methadone. Gonadectomy had a significant effect on the results of methadone treatment with respect to glutathione S-transferase activity in female rats. A sex difference was noted in the control levels of aryl hydrocarbon hydroxylase and glutathione S-transferase, but not of epoxide hydratase activity. The glutathione S-transferase and aryl hydrocarbon hydroxylase activities were decreased in castrated male rats, whereas epoxide hydratase activity was unaltered. It is concluded that sex hormones play an important role in the induction of epoxide hydratase and glutathione S-transferase by methadone, but not of aryl hydrocarbon hydroxylase, at this particular dosage regime.
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PMID:The effects of gonadectomy on the hepatic activities of aryl hydrocarbon hydroxylase, epoxide hydratase, and glutathione S-transferase in Wistar rats pretreated with oral methadone . HCl. 44 29

The binding of substrates and a product to glutathione S-transferase A from rat liver was studied by use of equilibrium dialysis and equilibrium partition in a two-phase system. The radioactive substrates glutathione and bromosulfophthalein as well as a product of glutathione and 3,4-dichloro-1-nitrobenzene, S-(2-chloro-4-nitrophenyl)glutathione, gave hyperbolic binding isotherms with a stoichiometry of 2 mol per mol of enzyme (i.e. 1 molecule per subunit). Glutathione (and glutathione disulfide) had an equilibrium (dissociation) constant for the binding of about 10 microM, whereas bromosulfophthalein and the product had equilibrium constants of about 0.5 microM. All ligands showed the same binding stoichiometry, and competition experiments involving unlabeled ligands indicated that glutathione and the glutathione derivatives were binding to the same site. Low affinity sites appeared to exist in addition to the specific high affinity sites (one per subunit) for all ligands tested. The binding studies are fully consistent with a steady state random kinetic mechanism for the enzyme.
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PMID:The binding of substrates and a product of the enzymatic reaction to glutathione S-transferase A. 45 71

The present study describes the effects of tetraethyl lead on various drug metabolizing enzymes in different tissues of the rat. Tetraethyl lead was administered intraperitoneally to rats (250 mumol/kg) on two consecutive days. The animals were killed on day 3. Tetraethyl lead-treatment decreased the concentration of hepatic cytochrome P-450 (to 45 per cent of the control), the hepatic activity of aryl hydrocarbon hydroxylase (to 41 per cent of the control) and ethoxycoumarin deethylase (to 45 per cent of the control). Epoxide hydratase activity was enhanced in the liver (1.3-fold), kidney (3.3-fold), and small intestinal mucosa (4.7-fold). The activity of glutathione S-transferase decreased in the liver (to 69 per cent of the control) but increased in the kidney (1.5-fold) and small intestinal mucosa (1.7-fold). The glucuronidation of o-aminophenol was enhanced (2.2-fold) in the kidney of tetraethyl lead treated rats. It is concluded that exposure to tetraethyl lead brings about widespread changes in the ability of mammals to detoxify foreign compounds.
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PMID:Effects of tetraethyl lead on the activities of drug metabolizing enzymes in different tissues of the rat. 47 47

An in vitro assay for the determination of the activity of disopyramide-N-dealkylation was developed. This reaction was concluded to be catalyzed by the liver microsomal, cytochrome P-450 centered monooxygenase system. Phenobarbital enhanced the N-dealkylation of disopyramide four fold, and disopyramide itself 1.6 fold, whereas methylcholanthrene was without effect. Disopyramide also increased ethoxycoumarin deethylation 1.6 fold, and had a slight increasing effect on the activity of epoxide hydratase, but did not affect the activities of glutathione S-transferase or UDPglucuronosyltransferase.
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PMID:Induction of disopyramide N-dealkylation by phenobarbital and disopyramide in rat liver. 48 13


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