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)

The initial enzymic step in mercapturic acid formation is catalyzed by glutathione S-transferase. Several species of this enzyme, designated as transferases alpha, beta, gamma, delta and epsilon on the basis of increasing isoelectric points, were isolated from human liver. Evidence is presented that each of the purified species is homogeneous with respect to sodium dodecylsulfate-gel electrophoresis. Transferases alpha, beta and epsilon each appear as a single band on gel electrofocusing; transferases gamma and delta are present as two and three bands, respectively, with each band catalytically active. Amino acid analysis indicated the five transferases to be either very closely related or identical in this respect. All enzyme species have a molecular weight of about 48500 and consist of two apparently identical subunits. The spectrum of substrates is the same for each although the enzymes differ slightly in specific activity. As is the case for the rat liver enzymes, each of the human transferases binds bilirubin although this compound is not a substrate.
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PMID:Multiple forms of human glutathione S-transferase and their affinity for bilirubin. 0 Dec 62

We have measured the activities of epoxide hydrase in microsomes and glutathione S-epoxidetransferase and glutathione S-aryltransferase in cytosol fractions of liver, lungs, kidneys, and small intestine from fetal and neonatal guinea pigs and rabbits. The rates at which adult values of these enzyme activities are reached in extrahepatic tissues differ from the rates of maturation of the hepatic enzyme activities for both species. In addition, the two pathways of epoxide metabolism studied here developed with age at different rates in any one organ. However, both cytosol glutathione S-transferases showed very similar developmental profiles in any one organ. It was especially interesting that the activities of both glutathione S-transferases were within the adult range in pulmonary cytosol fraction of guinea pig and rabbit before birth. Intestinal microsomes did not have adult values for epoxide hydrase activity until several weeks after birth. A feature common to both epoxide-metabolizing activities in hepatic and extrahepatic organs was a drop in mean specific activity, sometimes not statistically significant, around the time of birth. This decrease appeared to be due to dilution of the active enzyme with other protein, inasmuch as the total organ activity, in general, showed no such decline. We found that the pattern of development of hepatic microsomal epoxide hydrase activity was similar to developmental patterns published by others for hepatic microsomal mixed-function oxidases, and also that development of hepatic cytosol glutathione S-transferase was similar to hepatic development of glutathione S-transferase towards other substrates described in the literature.
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PMID:The perinatal development of epoxide-metabolizing enzyme activities in liver and extrahepatic organs of guinea pig and rabbit. 1 72

One of the main components in the waste products from vinyl chloride industries (EDC-tar), is ethylene dichloride (1,2-dichloroethane). This compound has been tested for mutagenicity on Salmonella typhimurium TA 1535. It is concluded that 1,2-dichloroethane gives a weak direct mutagenic effect, which is enhanced by addition of the postmitochondrial liver fraction (S-9). This activation is NADPH-independent and non microsomal. It is caused by a factor in the soluble fraction (115 000 g supernatant). This activation was further enhanced by the addition of glutathione but not by the addition of L-cysteine, N-acetyl-L-cysteine or 2-mercaptoethanol. No activation was observed when glutathione was added in the presence of a totally denaturated S-9 fraction or in the absence of this fraction. Activation of 1,2-dichloroethane was also found in the presence of glutathione and glutathione S-transferase A and C but not with glutathione S-tranferase B. A synthetic conjugate S-(2-chloroethyl)-L-cysteine gave a strong direct mutagenic effect at concentrations where no effects were seen with 1,2-dichloroethane. It is thus concluded that 1,2-dichloroethane is activated by conjugation to glutathione. Another main component in EDC-tar, 1,1,2-trichloroethane, was not mutagenic under any of our experimental conditions. For comparison 1,2-dibromoethane was also tested and gave a stronger direct mutagenic effect than 1,2-dichloroethane. Like the latter 1,2-dibromoethane was also activated by a NADPH-independent process.
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PMID:The mutagenic effect of 1,2-dichloroethane on Salmonella typhimurium I. Activation through conjugation with glutathion in vitro. 2 3

Crude cell-free extracts of nine strains of Streptomyces tested for nitroalkane-oxidizing activity showed production of nitrous acid from 2-nitropropane, 1-nitropropane, nitroethane, nitromethane, and 3-nitropropionic acid. These substrates were utilized in most strains but to a decreasing extent in the order given, and different strains varied in their relative efficiency of oxidation. p-Nitrobenzoic acid, p-aminobenzoic acid, enteromycin, and omega-nitro-l-arginine were not attacked. d-Amino acid oxidase, glucose oxidase, glutathione S-transferase, and xanthine oxidase, enzymes potentially responsible for the observed oxidations in crude cellfree extracts, were present at concentrations too low to play any significant role. A nitroalkane-oxidizing enzyme from streptozotocin-producing Streptomyces achromogenes subsp. streptozoticus was partially purified and characterized. It catalyzes the oxidative denitrification of 2-nitropropane as follows: 2CH(3)CH(NO(2))CH(3) + O(2) --> 2CH(3)COCH(3) + 2HNO(2). At the optimum pH of 7.5 of the enzyme, 2-nitropropane was as good a substrate as its sodium salt; t-nitrobutane was not a substrate. Whereas Tiron, oxine, and nitroxyl radical acted as potent inhibitors of this enzyme, superoxide dismutase was essentially without effect. Sodium peroxide abolished a lag phase in the progress curve of the enzyme and afforded stimulation, whereas sodium superoxide did not affect the reaction. Reducing agents, such as glutathione, reduced nicotinamide adenine dinucleotide, and nicotinamide adenine dinucleotide phosphate, reduced form, as well as thiol compounds, were strongly inhibitory, but cyanide had no effect. The S. achromogenes enzyme at the present stage of purification is similar in many respects to the enzyme 2-nitropropane dioxygenase from Hansenula mrakii. The possible involvement of the nitroalkane-oxidizing enzyme in the biosynthesis of antibiotics that contain a nitrogen-nitrogen bond is discussed.
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PMID:Nitroalkane oxidation by streptomycetes. 3 65

A proliferation-competent adult rat liver cell monolayer system has been analyzed for tissue-specific functions during its growth cycle. High levels of the adult (L type) form of pyruvate kinase (EC 2.7.1.40) and glutathione S-transferase B ("ligand," EC 2.5.1.18) are observed during the early lag phase; they decline markedly during the logarithmic phase and reappear during the stationary phase. By contrast, elevated levels of the fetal (K type) form of pyruvate kinase and alpha1-fetoprotein production appear only after proliferation begins; this pattern diminishes slightly during stationary phase as the adult phenotype is restored. Albumin production continues throughout the entire growth cycle. These in vitro findings simulate those observed during hepatoproliferative transitions in the intact animal and, as such, constitute a developmental program for normal epithelial cells in primary culture.
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PMID:Growth state-dependent phenotypes of adult hepatocytes in primary monolayer culture. 7 17

The prostaglandin D synthetase system was isolated from rat brain. Prostaglandin endoperoxide synthetase solubilized from a microsomal fraction catalyzed the conversion of arachidonic acid to prostaglandin H2 in the presence of heme and tryptophan. Prostaglandin D synthetase (prostaglandin endoperoxidase-D isomerase) catalyzing the isomerization of prostaglandin H2 to prostaglandin D2 was found predominantly in a cytosol fraction and was purified to apparent homogeneity with a specific activity of 1.7 mumol/min/mg of protein at 24 degrees C. The enzyme also acted upon prostaglandin G2 and produced a compound presumed to be 15-hydroperoxy-prostaglandin D2. Glutathione was not required for the enzyme reaction, but the enzyme was stabilized by thiol compounds including glutathione. The enzyme was inhibited by p-chloromercuribenzoic acid in a reversible manner. The purified enzyme was essentially free of the glutathione S-transferase activity which was found in the cytosol of brain.
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PMID:Purification and properties of prostaglandin D synthetase from rat brain. 10 31

The carcinogen 4-nitroquinoline 1-oxide (4-NQO) was found to rapidly deplete non-protein thiols (NPSH) from Ehrlich ascites tumor cells and V79 Chinese hamster fibroblasts. The effects of NPSH on 4-NQO metabolism were studied by measuring 4-hydroxyaminoquinoline 1-oxide formation, CN- -insensitive oxygen consumption, and reduction of ferricytochromes c + c1 in normal cells and in cells pretreated with the thiol reagent N-ethylmaleimide. Removal of thiols before treatment with 4-NQO resulted in increased production of 4-hydroxyaminoquinoline 1-oxide and increased production of nitro radicals. The NPSH thus appeared to play a significant role in 4-NQO detoxification. Glutathione, when present in culture medium during 4-NQO treatment, protected V79 cells from 4-NQO toxicity. Several mechanisms for reaction of 4-NQO with intracellular NPSH were indicated. Both V79 and Ehrlich cells contained appreciable amounts of glutathione S-transferase (EC 2.5.1.18), which catalyzes the nucleophilic substitution of the nitro group of 4-NQO with thiols. Greater thiol loss under oxic than under hypoxic conditions suggested oxidation by superoxide, peroxide, or hydroxyl radical formed in the course of 4-NQO reduction. In addition, reaction of thiols with nitro radicals or with nitrosoquinoline 1-oxide was indicated by the inhibitory effect of glutathione on oxygen consumption in solutions of 4-NQO and sodium ascorbate.
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PMID:Interactions of the carcinogen 4-nitroquinoline 1-oxide with the non-protein thiols of mammalian cells. 11 Apr 43

Polybrominated biphenyls (PBBs) are structurally very close to polychlorinated biphenyls (PCBs) which are known to be potent inducers of xenobiotic biotransformation reactions. We have studied the effects of 2 industrial PBB-mixtures, "hexabromobiphenyl" (HBB) and "octabromobiphenyl" (OBB), on enzymes catalyzing drug hydroxylation, epoxide hydration, and conjugation reactions in different tissues of C57 mice. The enzyme activities were measured 10 days after a single i.p. injection of PBBs (75 mg/kg). HBB enhanced the activities of hepatic AHH (1.9-fold), ethoxycoumarin deethylase (5.7-fold), epoxide hydratase (1.5-fold), glutathione S-transferase (1.7-fold) and UDP-glucuronosyltransferase (1.5-fold). In the kidney HBB enhanced the activity of UDP-blucuronosyltransferase 1.5-fold. OBB caused in increase in the activities of liver AHH (1.5-fold), ethoxycoumarin deethylase (2.4-fold) and glutathione S-transferase (1.4-fold). A slight increase was also seen in the activity of UDP-glucuronosyltransferase in digitoninactivated liver microsomes of OBB-treated mice. In the kidney OBB caused a slight but statistically significant decrease in glutathione S-transferase activity. Intraperitoneally injected bromobiphenyls had no effects on these drug metabolizing enzymes in the lung of C57 mice. These results were similar to the effects caused by a mixture of PCBs.
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PMID:Effect of polybrominated biphenyls on drug metabolizing enzymes in different tissues of C57 mice. 21 61

Soluble, glutathione-stimulated delta 5-3-ketosteroid isomerase (EC 5.3.3.A) activity of human and rat liver resides in very basic proteins with molecular weights of about 45,000 which are present in high concentrations in these tissues. Physiochemical and immunological evidence is presented for the identity of the proteins responsible for this enzymatic activity with the glutathione S-transferases (RX:glutathione R-transferase, EC 2.5.1.18) that conjugate glutathione with a variety of electrophilic compounds. In the rat, the steroid isomerase is associated principally with the major transferase (B), which is also known as ligandin, and has the versatility to bind various hydrophobic compounds such as bilirubin, corticosteroids, and metabolites of a number of carcinogens. Other rat liver-glutathione S-transferase species are far less active in the steroid isomerization reaction. The delta 5-3-ketosteroid isomerase activity of human liver is more uniformly distributed among the five glutathione S-transferases that have been described. Steroid isomerization differs fundamentally from other reactions promoted by glutathione S-transferases in that glutathione is not consumed in the reaction. However, because the transferase enzymes promote nucleophilic attack by glutathione on a variety of largely foreign organic substrates, a similar mechanism may be involved in the isomerase reaction. Delta 5-3-ketosteroids are among the few known naturally occurring substrates for these enzymes.
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PMID:Relationship between the soluble glutathione-dependent delta 5-3-ketosteroid isomerase and the glutathione S-transferases of the liver. 26 70

Poly(A)-containing rat liver mRNA isolated from animals injected with phenobarbital and uninjected controls was translated efficiently in a wheat-germ system. The synthesis of ligandin (glutathione S-transferase B; glutathione transferase; RX-gluathione R-transferase, EC 2.5.1.18) was detected by immunoprecipitation with a highly purified monospecific ligandin antibody and analysis by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The extent of incorporation of [35S]methionine into ligandin in the translation system was similar for poly(A)-containing messages from un-infected animals and those treated with phenobarbital.
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PMID:Translation in vitro of rat liver messenger RNA coding for ligandin (glutathione S-transferase B). 26 12


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