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)

trans-Stilbene imine (trans-1,2-diphenylaziridine) is the nitrogen analog of trans-stilbene oxide, a potent inducer of several microsomal and cytosolic xenobiotic-metabolizing enzymes. Although the acute toxicity of cis- and trans-stilbene imines prevents their application at the usual dose for trans-stilbene oxide (400 mg/kg/day), it is apparent that the imines nevertheless potently induce several xenobiotic-metabolizing enzymes in rat liver. The IP administration of trans-stilbene imine resulted in statistically significant increases in the activities of aminopyrine N-demethylase, microsomal epoxide hydrolase, glutathione transferase (toward 1-chloro-2,4-dinitrobenzene, 1,2-dichloro-4-nitrobenzene and delta 5-androstene-3,17-dione) and UDP-glucuronosyltransferase (toward testosterone). cis-Stilbene imine was less potent in inducing these activities. Although trans-stilbene imine (total dose = 400 mg/kg) was more potent than trans-stilbene oxide (total dose = 1200 mg/kg) in inducing the activities of glutathione transferase (toward 1-chloro-2,4-dinitrobenzene) and UDP-glucuronosyltransferase (toward testosterone), both compounds belong to the class of substances which are more potent inducers of conjugating (phase II) enzymes. Because of their structural similarity with K-region arene imines which are potent mutagens, cis-stilbene imine and trans-stilbene imine were investigated for mutagenicity (reversion of his- strains of Salmonella typhimurium). cis-Stilbene imine and trans-stilbene imine were direct mutagens in the strain TA100. This result, and the finding that acenaphthene 1,2-imine efficiently reverts various strains of Salmonella typhimurium, demonstrates that not only K-region arene imines, but also other aziridines substituted at the two carbons with aromatic moieties, are mutagenic.
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PMID:cis- and trans-1,2-diphenylaziridines: induction of xenobiotic-metabolizing enzymes in rat liver and mutagenicity in Salmonella typhimurium. 354 49

Tumor cell resistance to alkylating agents was studied by examining Walker 256 rat mammary carcinoma cells differentially sensitive to nitrogen mustards. A resistant subpopulation (WR) was selected by exposure to chlorambucil. WR cells showed approximately a 15-fold resistance to the cytotoxic effects of nitrogen mustards and elevated glutathione S-transferase (GST) activity when compared to the sensitive parent cell line (WS). To extend these findings, the GSTs from WR and WS were purified by affinity chromatography on S-hexylglutathione coupled to epoxy-activated agarose. Substrate specificity experiments using purified GSTs demonstrated different profiles of enzyme activity for WR and WS and suggested differential isoenzyme expression in these two cell lines. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis revealed that the major GST present in both WR and WS was a 26,000-Da subunit that was immunologically distinct from the rat liver GSTs. This GST subunit cross-reacted with antibodies against anionic human placental GST. In addition, three GST forms common to rat liver (29,500, 28,500 and 27,500 molecular weight) were also identified. Overexpression of the 29,500-Da protein was observed in WR cells. These data suggest that differential expression of GST subunits may contribute to the nitrogen mustard-resistant phenotype.
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PMID:Glutathione S-transferases in nitrogen mustard-resistant and -sensitive cell lines. 360 Jun 2

We have reported previously (C. N. Robson et al., Cancer Res., 46: 6290-6294, 1986) the isolation of a Chinese hamster ovary cell line, designated CHO-Chlr, that exhibits resistance to bifunctional nitrogen mustards while maintaining the normal parental level of sensitivity to several other alkylating agents. We have compared the rate of formation and repair of DNA cross-links induced by mechlorethamine in CHO-Chlr and parental CHO-K1 cells, both in intact cells and in isolated nuclei. Equimolar doses of mechlorethamine induce significantly fewer DNA interstrand cross-links in CHO-Chlr cells than in CHO-K1 cells, but levels of DNA-protein adducts are approximately equivalent in the two lines. There is a correlation between the relative resistance of CHO-Chlr cells to mechlorethamine (34-fold) and the amount of drug required to induce approximately equal numbers of DNA interstrand cross-links in the two cell lines. This strongly implicates DNA-DNA adducts in the cytotoxic action of mechlorethamine. DNA cross-linking studies on isolated nuclei reveal only minor differences between the two lines even with identical drug treatments. The rate of cross-link repair is comparable in the two cell lines. These results, taken together with our earlier observation that the rate of drug accumulation is identical in these two lines, suggest that enhanced cytoplasmic drug detoxification is the underlying resistance mechanism in CHO-Chlr cells. We have measured cellular glutathione S-transferase activity, using both the general substrate 1-chloro-2,4-dinitrobenzene, and substrates with some specificity for the different classes of transferase isoenzymes. Total enzyme activity (as measured with 1-chloro-2,4-dinitrobenzene) is elevated 3-fold in the resistant cells. A 2- and 5-fold increase, respectively, in activity against ethacrynic acid and cumene hydroperoxide is detectable in CHO-Chlr cells. This elevation in catalytic activity in the resistant cells is reflected in higher levels of both the Yf- and Ya-type transferase subunits.
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PMID:Reduced levels of drug-induced DNA cross-linking in nitrogen mustard-resistant Chinese hamster ovary cells expressing elevated glutathione S-transferase activity. 366 6

The reaction of 1,2-dibromoethane and glutathione with DNA in the presence of glutathione S-transferase results in the formation of a single major DNA adduct, which can be released by thermal hydrolysis at neutral pH and separated by octadecylsilyl and propylamino high-performance liquid chromatography. The same DNA adduct is the only major one formed in livers of rats treated with 1,2-dibromo[1,2-14C]ethane. The DNA adduct was identified as S-[2-(N7-guanyl)ethyl]glutathione: (1) The chromatographic behavior was altered by treatment with gamma-glutamyl transpeptidase or Streptomyces griseus protease. (2) The molecular ions observed in positive and negative mode fast atom bombardment mass spectrometry were those expected for the structure when either glycerol or a mixture of dithiothreitol and dithioerythritol was used as the bombardment matrix. (3) The two-dimensional 1H NMR correlated spectroscopy spectrum of the DNA adduct was compared to the spectra of glutathione, oxidized glutathione, and N7-methylguanine and found to be consistent with the assigned structure. No evidence for in vitro or in vivo opening of the guanyl imidazole ring was observed under these conditions. The structure of the adduct supports a pathway involving enzyme-catalyzed conjugation of 1,2-dibromoethane with glutathione, non-enzymatic dehydrohalogenation of the resulting half-mustard to form a cyclic episulfonium ion, and attack of the N7 nitrogen of DNA guanine on the episulfonium ion to generate this major DNA adduct, which may be related to the carcinogenicity of this chemical.
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PMID:S-[2-(N7-guanyl)ethyl]glutathione, the major DNA adduct formed from 1,2-dibromoethane. 370 41

The stereoselectivity of the closely related isozymes A2 and C2 of rat liver glutathione S-transferase toward several arene and azaarene oxides is examined. Isozyme C2 is stereospecific, catalyzing attack of glutathione at the oxirane carbon of R absolute configuration for a series of K-region arene oxides including phenanthrene 9,10-oxide, 1. Substitution of nitrogen in the biphenyl system of 1 causes a loss in stereospecificity. Isozyme A2 exhibits a low degree of stereoselectivity toward both arene and azaarene oxides. Kinetic studies of the two isozymes show that although isozyme C2 turns over 1 faster than does isozyme A2 the opposite is true when 4,5- diazaphenanthrene 9,10-oxide is the substrate. The kinetic and stereochemical behavior of the homodimeric isozymes A2 and C2 can be used to predict the stereoselectivity of the heterodimeric isozyme AC perhaps suggesting that catalysis is insensitive to different subunit-subunit interactions in the three isozymes.
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PMID:Investigation of the kinetic and stereochemical recognition of arene and azaarene oxides by isozymes A2 and C2 of glutathione S-transferase. 643 Feb 88

Three of the isozymes of glutathione S-transferase (EC 2.5.1.18) from rat liver (isozymes A, B, and C) catalyze the addition of glutathione to phenanthrene 9, 10-oxide with varying degrees of efficiency and stereoselectivity. Isozyme C is 2-fold and 35-fold more efficient toward this substrate than are isozymes A and B, respectively, and gives a 20 to 1 ratio of the two possible diastereomeric products. The stereoselectivities of isozymes A (approximately 1 to 1) and B (3 to 1) are considerably lower. The major product diastereomer from isozyme C is deduced to have the 9S, 10S absolute configuration by circular dichroism spectroscopy, implying attack of glutathione on the oxirane carbon on R absolute configuration. Isozyme C shows little kinetic discrimination between other K-region arene oxides such as pyrene 4,5-oxide and the enantiomers of benz[a]anthracene 5,6-oxide and benzo[a]pyrene 4,5-oxide. However, the stereoselectivity toward all the substrates is conserved with predominant (greater than 95%) attack at the oxirane carbon of R absolute configuration to give the S,S product. The stereoselectivity of isozyme C is very sensitive to the introduction and location of nitrogen substitution in the phenyl rings of phenanthrene 9,10-oxide. As a result isozyme C shows little or no stereoselectivity toward 4,5-diaza- and 4-azaphenanthrene 9,10-oxide. In contrast, 1-azaphenanthrene 9,10-oxide is attacked preferentially at the R carbon of the oxirane. The results suggest that hydrophobic interactions between the enzyme surface and the substrate distal to the oxirane ring are important in determining the stereoselectivity of the enzyme toward arene oxides.
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PMID:Stereoselectivity of isozyme C of glutathione S-transferase toward arene and azaarene oxides. 683 24

Strain differences of mice in their susceptibility to nitrogen dioxide (NO2) were examined by measuring the activities of antioxidative protective enzymes, and the amounts of antioxidants and lipid peroxides in lungs. Four strains of mice: ICR, BALB/c, ddy and C57BL/6 were used in this study and their LC50 values after exposure to NO2 for 16 hr were: 38, 49, 51 and 64 ppm, respectively (1). Genetic strain differences were observed in the enzyme activities, the antioxidant contents and lipid peroxide contents among these four different strains. The activities of glutathione peroxidase (GPX), glutathione S-transferase, and superoxide dismutase (SOD), and the contents of non-protein sulfhydryls (NPSH), alpha-tocopherol (alpha-Toc) and total lipids in lungs of the four strains were related to their LC50, while TBA reactants in lungs of the four strains were inversely related to their LC50. After exposure to 20 ppm NO2 for 16 hr, the activities of the protective enzymes and the contents of NPSH decreased, while the level of alpha-Toc increased markedly. The activities of GPX, 6-phosphogluconate dehydrogenase, SOD and disulfide reductase, and the contents of NPSH, alpha-Toc and total lipids were also related to their LC50. On the other hand, TBA reactants increased higher than those of the control groups and were inversely related to their LC50. These results suggest that the protective enzymes and the antioxidants are important factors at defence mechanism in lungs to NO2 and that the intensity of the protective systems in pigmented strains is generally greater than that in albino strains.
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PMID:Biochemical studies on strain differences of mice in the susceptibility to nitrogen dioxide. 717 5

trans-Stilbene oxide has been found to be a new type of inducer of drug-metabolizing systems. In order to identify the true inducer and to determine the structural requirements for induction, rats were treated with metabolites and structural analogues of stilbene. Subsequently, hepatic levels of cytochrome P-450, microsomal epoxide hydrolase, and cytoplasmic glutathione S-transferase were assayed. All three enzymes were induced by cis- and trans-stilbene and cis- and trans-stilbene oxide. In addition, epoxide hydrolase and glutathione S-transferase activities were induced by benzoin and benzil. In contrast, the diols and benzoic acid had little, if any, effect. The main conclusions drawn from these findings are that: (1) trans-stilbene oxide itself seems to be the inducer of drug-metabolizing enzymes; and (2) benzil is more selective as an inducer of epoxide hydrolase than is trans-stilbene oxide. Attempts to induce epoxide hydrolase with other structural analogues of stilbene led to the following conclusions: (1) two phenyl rings are required for induction; (2) the induction is not as great if the rings are substituted or one of the ring carbon atoms is replaced by a nitrogen; (3) a carbon bridge between the phenyl groups generally results in a greater induction, especially if the bridge contains an epoxy group or one or two keto groups.
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PMID:Induction of drug-metabolizing systems and related enzymes with metabolites and structural analogues of stilbene. 721 12

The niaD and niiA genes of Aspergillus nidulans, which code, respectively, for nitrate and nitrite reductases, are divergently transcribed, and their ATGs are separated by 1,200 bp. The genes are under the control of the positively acting NirA transcription factor, which mediates nitrate induction. The DNA binding domain of NirA was expressed as a fusion protein with the glutathione S-transferase of Schistosoma japonicum. Gel shift and footprint experiments have shown that in the intergenic region there are four binding sites for the NirA transcription factor. These sites can be represented by the nonpalindromic consensus 5'CTCCGHGG3'. Making use of a bidirectional expression vector, we have analyzed the role of each of the sites in niaD and niiA expression. The sites were numbered from the niiA side. It appeared that site 1 is necessary for the inducibility of niiA only, while sites 2, 3, and to a lesser extent 4 (which is nearer to and strongly affects niaD) act bidirectionally. The results also suggest that of the 10 binding sites for the AreA protein, which mediates nitrogen metabolite repression, those which are centrally located are physiologically important. The insertion of an unrelated upstream activating sequence into the intergenic region strongly affected the expression of both genes, irrespective of the orientation in which the element was inserted.
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PMID:The intergenic region between the divergently transcribed niiA and niaD genes of Aspergillus nidulans contains multiple NirA binding sites which act bidirectionally. 756 20

Glutathione S-transferases (EC 2.5.1.18) in mammalian cells catalyze the conjugation, and thus, the detoxication of a structurally diverse group of electrophilic environmental carcinogens and alkylating drugs, including the antineoplastic nitrogen mustards. We proposed that structural alteration of the nonspecific electrophile-binding site would produce mutant enzymes with increased efficiency for detoxication of a single drug and that these mutants could serve as useful somatic transgenes to protect healthy human cells against single alkylating agents used in cancer chemotherapy protocols. Random mutagenesis of three regions (residues 9-14, 102-112, and 210-220), which together compose the glutathione S-transferase electrophile-binding site, followed by selection of Escherichia coli expressing the enzyme library with the nitrogen mustard mechlorethamine (20-500 microM), yielded mutant enzymes that showed significant improvement in catalytic efficiency for mechlorethamine conjugation (up to 15-fold increase in kcat and up to 6-fold increase in kcat/Km) and that confer up to 31-fold resistance, which is 9-fold greater drug resistance than that conferred by the wild-type enzyme. The results suggest a general strategy for modification of drug- and carcinogen-metabolizing enzymes to achieve desired resistance in both prokaryotic and eukaryotic plant and animal cells.
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PMID:Forced evolution of glutathione S-transferase to create a more efficient drug detoxication enzyme. 766 59


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