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)

We have examined the mercapturic acid pathway of the cataractous rabbit lens following induction by naphthalene as an oxidative foreign substance. 1,2-Naphthoquinone, which is formed in the eye from naphthalene diol and other naphthalene derivatives by a combination of enzymic and non-enzymic reactions, readily oxidizes GSH and GSH S-transferase [EC 2.5.1.18] in the lens scavenging system. 1,2-Naphthoquinone appeared in the rabbit aqueous humor after 8 h, and showed a maximum level in the lens 24 h after naphthalene administration, with marked accumulation in the lens nucleus. At the same time, the GSH level and GSH S-transferase activity in the lens decreased after 4 h, and lens opacification appeared 7 days after naphthalene administration. Furthermore, we identified the naphthalene metabolite, N-acetyl-S-(1,2-dihydro-2-hydroxynaphthyl) cysteine, in the lens of rabbit after naphthalene administration and in an in vitro experiment on lens homogenate using gas chromatography-mass spectrometry (GC-MS). This compound is an intermediate of the mercapturic acid pathway, and indicates that naphthalene derivatives are metabolized through the mercapturic acid pathway which acts as a scavenging system in the lens.
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PMID:Studies on the mercapturic acid pathway in the rabbit lens. 318 30

Pyloric caeca of trout contain 1.9 mmol GSH/kg tissue. Cytosolic glutathione S-transferase activity with 1-chloro-2,4-dinitrobenzene as substrate is 0.06 mmol/min/g protein. Cholate (3.3 mM) inhibits cytosolic transferase activity by 55% at pH 6.6 and by 4% at pH 7.4. The transferases do not bind 8-anilino-1-naphthalene sulphonate at pH 7.4. The cytosolic transferases are inactivated progressively by 1-chloro-2,4-dinitrobenzene, 50% of their activity being lost in 5.0 min. A minority of the activity does not bind to a glutathione-affinity matrix. At pH 6.6 its apparent Michaelis constants for GSH and 1-chloro-2,4-dinitrobenzene are 0.88 and 9.1 mM respectively. The rest of the activity is eluted from the affinity matrix as a single peak. Its apparent Michaelis constants for GSH and 1-chloro-2,4-dinitrobenzene are 0.33 and 2.9 mM respectively. Its subunit Mr is 22.4 kDa.
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PMID:The glutathione S-transferase activity in the pyloric caeca of rainbow trout, Salmo gairdneri. 370 15

The equilibrium binding of the non-substrate ligands 8-anilino-1-naphthalene sulfonate and bromosulfophthalein to porcine class pi glutathione S-transferase (pGSTP1-1) was studied using a variety of techniques (size-exclusion HPLC, steady-state fluorescence, second-derivative spectroscopy, and chemical modification of cysteines). Both ligands share the same binding site which has a highly hydrophobic surface. Occupation of the site inhibits catalytic function with glutathione and 1-chloro-2,4-dinitrobenzene in a non-competitive manner. Data obtained from different structural probes either located at strategic regions of pGSTP1-1 (Trp-28, Trp-38 and Cys-45) or distributed throughout the protein molecule (tyrosine residues) suggest that binding induces a microstructural change that impacts on the functional conformation of the active site.
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PMID:Porcine class pi glutathione S-transferase: anionic ligand binding and conformational analysis. 769 12

The octopine synthase (ocs or ocs-like) element has been previously reported to be responsive to the plant hormones, auxin, salicylic acid, and methyl jasmonate. Using transient assays with carrot protoplasts, we have demonstrated that an ocs element from the soybean auxin-inducible GH2/4 promoter is not only activated by strong auxins (i.e., 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, alpha-naphthalene acetic acid) and salicylic acid, but also by weak auxin analogues (beta-naphthalene acetic acid), inactive auxin analogs (i.e., 2,3-dichlorophenoxyacetic acid, 2,4,6-trichlorophenoxyacetic acid), and inactive salicylic acid analogs (3-hydroxybenzoic acid and 4-hydroxybenzoic acid). Our results indicate that the ocs element in the GH2/4 promoter is not selectively induced by plant hormones and might function similarly to tandem AP-1 sites in some animal glutathione S-transferase (GST) genes. The ocs element, like the AP-1 sites in animal GST promoters, may be induced not only by certain hormones but also by some non-hormonal stress-inducing or electrophilic agents.
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PMID:The ocs element in the soybean GH2/4 promoter is activated by both active and inactive auxin and salicylic acid analogues. 781 65

Parenteral administration of naphthalene produces a dose-dependent and tissue-, species-, and cell-selective lesion of murine Clara cells. The rate and stereoselectivity of naphthalene metabolism by microsomal preparations correlate with tissue and species differences in cytotoxicity. Because earlier studies used microsomes obtained from whole tissue, differences in susceptibility of proximal and distal airways could not be related to differences in the metabolic activation or detoxication of naphthalene. Specific subcompartments of the respiratory system, obtained by microdissection, have been used to study the cytochrome P450-dependent metabolism of naphthalene and the epoxide hydrolase/glutathione transferase-dependent metabolism of naphthalene oxide. The rates of naphthalene metabolism were substantially higher in mouse airways than in comparable airways of hamsters or rats. Rates of metabolism were higher in distal airways than in the trachea of all species studied. Metabolism in mouse airways was highly stereoselective, whereas that in hamster and rat tissues was not. Nonciliated cells at all airway levels in mice were heavily labeled with an antibody to cytochrome P450 2F2; little labeling was observed in any portion of rat and hamster lungs. Postmitochondrial supernatants prepared from mouse and hamster airways metabolized racemic naphthalene oxide to diol and glutathione adducts at substantially higher rates than did comparable preparations from rats. Although glutathione levels varied 2-4-fold at different airway levels in the three species studied, levels at the most susceptible site (mouse distal bronchioles) were as high as or higher than those at other, less susceptible, sites. These studies support the view that the rate and stereoselectivity of naphthalene metabolism to naphthalene 1R,2S-oxide catalyzed by cytochrome P450 2F2 are critical determinants in the species-specific and region-selective cytotoxicity of naphthalene in mice. The lack of major differences in the catalytic activity or enantioselectivity of putative detoxication enzymes (epoxide hydrolase or glutathione transferases) between mouse and hamster tissue, combined with data showing that the differences in the metabolic fate of naphthalene oxide in proximal versus distal airways are not dramatic, suggests that the initial epoxidation of naphthalene is an important factor in site-selective toxicity. These studies support the need to use tissue from defined airway levels for studies on the relationship of biochemical and metabolic factors important in cellular injury by lung toxicants, such as naphthalene, where there are dramatic regional differences in susceptibility to injury within the respiratory system.
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PMID:Relationship of cytochrome P450 activity to Clara cell cytotoxicity. IV. Metabolism of naphthalene and naphthalene oxide in microdissected airways from mice, rats, and hamsters. 783 35

The first step in retinoid action is binding to their nuclear receptors. Therefore, characterization of binding characteristics of retinoids is of major importance. Human retinoic acid receptors alpha (hRAR alpha), hRAR beta, and mouse RAR gamma (mRAR gamma) were expressed heterologously in Escherichia coli as a recombinant glutathione S-transferase (GST) fusion protein. The expressed fusion proteins were functional and bound specifically to the all-trans-retinoic acid (RA). The dissociation constants (Kd) for RA were 1.4 nM for GST-hRAR alpha, 1.4 nM for GST-hRAR beta, and 3.3 nM for GST-mRAR gamma, respectively. The fusion proteins were further used for competitive displacement assays to determine the displacement constant (DC50) for other selected retinoids. All-trans-RA and 4-oxo-all-trans-RA have high affinity with all three receptors (DC50 = 0.8-55 nM). The 13-cis RA binds to hRAR alpha with low affinity, but not to other RARs evaluated here. All-trans-N-ethylretinamide, all-trans-retinylacetate, and an ethyl ester of tetrahydronaphthalene derivative had no affinity to any RARs. The hRAR alpha and mRAR gamma receptors did not bind a naphthalene carboxylic acid derivative of RA, but hRAR beta binds this chemical with high affinity. Results indicated that the three recombinant proteins were functional in binding various RA congeners. The affinity and binding data of these retinoids were compared to their observed teratogenic activity.
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PMID:Characterization of heterologously expressed recombinant retinoic acid receptors with natural or synthetic retinoids. 785 57

Chemically reactive epoxide metabolites have been implicated in various forms of drug and chemical toxicity. Naphthalene, which is metabolized to a 1,2-epoxide, has been used as a model compound in this study in order to investigate the effects of perturbation of detoxication mechanisms on the in vitro toxicity of epoxides in the presence of human liver microsomes. Naphthalene (100 microM) was metabolized to cytotoxic, protein-reactive and stable, but not genotoxic, metabolites by human liver microsomes. The metabolism-dependent cytotoxicity and covalent binding to protein of naphthalene were significantly higher in the presence of phenobarbitone-induced mouse liver microsomes than with human liver microsomes. The ratio of trans-1,2-dihydrodiol to 1-naphthol was 8.6 and 0.4 with the human and the induced mouse microsomes, respectively. The metabolism-dependent toxicity of naphthalene toward human peripheral mononuclear leucocytes was not affected by the glutathione transferase mu status of the co-incubated cells. Trichloropropene oxide (TCPO; 30 microM), an epoxide hydrolase inhibitor, increased the human liver microsomal-dependent cytotoxicity (19.6 +/- 0.9% vs 28.7 +/- 1.0%; P = 0.02) and covalent binding to protein (1.4 +/- 0.3% vs 2.8 +/- 0.2%; P = 0.03) of naphthalene (100 microM), and reversed the 1,2-dihydrodiol to 1-naphthol ratio from 6.6 (without TCPO) to 2.6, 0.6 and 0.1 at TCPO concentrations of 30, 100 and 500 microM, respectively. Increasing the human liver microsomal protein concentration reduced the cytotoxicity of naphthalene, while increasing its covalent binding to protein and the formation of the 1,2-dihydrodiol metabolite. Co-incubation with glutathione (5 mM) reduced the cytotoxicity and covalent binding to protein of naphthalene by 68 and 64%, respectively. Covalent binding to protein was also inhibited by gestodene, while stable metabolite formation was reduced by gestodene (250 microM) and enoxacin (250 microM). The study demonstrates that human liver cytochrome P450 enzymes metabolize naphthalene to a cytotoxic and protein-reactive, but not genotoxic, metabolite which is probably an epoxide. This is rapidly detoxified by microsomal epoxide hydrolase, the efficiency of which can be readily determined by measurement of the ratio of the stable metabolites, naphthalene 1,2-dihydrodiol and 1-naphthol.
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PMID:An investigation of the formation of cytotoxic, genotoxic, protein-reactive and stable metabolites from naphthalene by human liver microsomes. 824 Apr 7

Two glutathione S-transferase (GST) isozymes, GST-rl1 and GST-rl2, were purified from rabbit lenses and their properties were compared with those of other animals. GST-rl1 and GST-rl2 are dimeric enzymes whose subunit sizes are 24,000 and 21,500, respectively. The substrate specificities and inhibitor sensitivities of GST-rl1 and GST-rl2 are different from each other and from those of the isozymes from other animals. GST-rl1 immunologically crossreacted with the antibody against class mu GST (rat GST Yb1-Yb1), and GST-rl2 crossreacted with the antibody against class pi GST (rat GST Yp-Yp). N-Terminal amino acid sequences of GST-rl1 and GST-rl2 have great homology with other class mu and class pi enzymes, and thus indicate that they belong to class mu and class pi, respectively. Class pi GST-rl2 is inactivated by 1,2-naphthoquinone, an oxidized metabolite of naphthalene, but class mu GST-rl1 is insensitive to it. These results are similar to those of class pi pig lens GST and class mu bovine lens GST. Thus, the expression pattern of GST isozymes in lens varies with animal species, and may relate to their variation in sensitivity to oxidative stress.
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PMID:Comparison of purified lens glutathione S-transferase isozymes from rabbit with other species. 831 92

Porcine and bovine lens GSTs were compared in the stability against various oxidative stress which is a major factor of cataract formation in order to clarify the role of lens glutathione S-transferase (GST) and its relation to cataractogenesis. Class pi porcine lens GST was inactivated reversibly by biological disulfides, cystine and cystamine, and also inactivated by active oxygen species such as O2- generated through xanthine-xanthine oxidase system and H2O2. On the other hand, class mu bovine lens GST was insensitive to such applied oxidative stress. Furthermore, 1,2-naphthoquinone, which is a metabolite of naphthalene and an actual inducer of naphthalene cataract, strongly inactivated porcine lens GST though it did not affect bovine enzyme. Thus, porcine and bovine lens GSTs had different sensitivity to various oxidative stress which could induce cataract formation. The results suggest that the differential expression of GST isozymes among animals may explain the variation in the cataract formation caused by oxidative stress.
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PMID:Difference in glutathione S-transferase response to oxidative stress between porcine and bovine lens. 847 85

The herpes simplex virus type 1 protease is expressed as an 80,000-dalton polypeptide, encoded within the 635-amino acid open reading frame of the UL26 gene. The two known protein substrates for this enzyme are the protease itself and the capsid assembly protein ICP35 (Liu, F., and Roizman, B. (1991) J. Virol. 65, 5149-5156). In this report we describe the use of a rapid and quantitative assay for characterizing the protease. The assay uses a glutathione S-transferase fusion protein containing the COOH-terminal cleavage site of ICP35 as the substrate (GST-56). The protease consists of N0, the NH2-terminal 247 amino acid catalytic domain of the UL26 gene product, also expressed as a GST fusion protein. Upon cleavage with N0, a single 25-mer peptide is released from GST-56, which is soluble in trichloroacetic acid. Using this assay, the protease displayed a pH optimum between 7 and 9 but most importantly had an absolute requirement for high concentrations of an antichaeotrophic agent. Strong salting out salts such as Na2SO4 and KPO4 (> or = 1 M) stimulated activity, whereas NaCl and KCl had no effect. The degree of stimulation by 1.25 M Na2SO4 and KPO4 were 100-150- and 200-300-fold, respectively. Using the fluorescent probe 1-anilino-8-naphthalene sulfonate, the protease was shown to bind the dye in the presence of 1.25 M Na2SO4 or KPO4, but not at low ionic strength or in the presence of 1.25 or 2.2 M NaCl. This binding was most likely at the protease active site because a high affinity cleavage site peptide, but not a control peptide, could displace the dye. In addition to cleaving GST-56, the herpes simplex virus type I protease also cleaved the purified 56-mer peptide. Circular dichroism and NMR spectroscopy showed the peptide to be primarily random coil under physiological conditions, suggesting that antichaeotrophic agents affect the conformation of the substrate as well as the protease.
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PMID:Stimulation of the herpes simplex virus type I protease by antichaeotrophic salts. 853 Apr 25


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