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)

The ras oncogene family has been implicated in tumor resistance to ionizing radiotherapy. Using the gene-transfer model, we show here that ras expression may also affect cell responses to chemical inducers of oxidative stress. Studies involving human osteosarcoma subclones, which vary in their levels of EJras expression, revealed a tight correlation between the amounts of ras-encoded mRNA and p21 produced, and the degree of resistance to doxorubicin or hydrogen peroxide. Differences in response could not be explained by increased activity of anti-oxidant enzymes such as superoxide dismutase, glutathione reductase, glutathione S-transferase or glutathione peroxidase. Moreover, there were no significant differences in glutathione levels. Although the resistant cells had elevated levels of gamma-glutamyl-transferase mRNA indicative of an increased rate of glutathione turnover, this elevation was not specific for ras-transfected cell lines. Lovastatin, an inhibitor of protein isoprenylation critical for p21ras membrane association and function, restored the sensitivity of ras-transformed cells to doxorubicin and hydrogen peroxide. The data indicate that pharmacological agents affecting ras expression may enhance responses of some human tumors to free-radical-mediated chemotherapies.
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PMID:Tumor resistance to oxidative stress: association with ras oncogene expression and reversal by lovastatin, an inhibitor of p21ras isoprenylation. 782 24

Neutrophil inhibitory factor (NIF) is a hookworm-derived glycoprotein ligand of the integrin CD11b/CD18 that inhibits human neutrophil function (Moyle, M., Foster, D. L., McGrath, D. E., Brown, S. M., Laroche, Y., De Meutter, J., Stanssens, P., Bogowitz, C. A., Fried, V. A., Ely, J. A., Soule, H. R., and Vlasuk, G. P. (1994) J. Biol. Chem. 269, 1008-10015). Here, we present evidence that recombinant NIF (rNIF) associates with the approximately 200-amino acid residue I domain of CD11b/CD18 and that this interaction is essential for inhibition of neutrophil function by NIF. First, radiolabeled rNIF binds to a recombinant glutathione S-transferase fusion protein that contains the CD11b I domain. This high affinity interaction has a partial dependence on divalent cations. The association of rNIF with the CD11b I domain is specific because 125I-rNIF does not bind either a glutathione S-transferase fusion protein that contains the I domain of the integrin CD11a/CD18 or recombinant glutathione S-transferase without the I domain. Second, the CD11b I domain fusion protein effectively competes with CD11b/CD18 on human neutrophils for 125I-rNIF binding. Third, the CD11b I domain fusion protein blocks the inhibition of certain neutrophil functions by rNIF, including adhesion of neutrophils to human endothelial cell monolayers and adhesion-dependent release of hydrogen peroxide from neutrophils. Specificity is demonstrated by the inability of the CD11a I domain fusion protein to block either rNIF binding to neutrophils or rNIF activity. Fourth, rNIF blocks the interaction between neutrophils and fibrinogen, a CD11b/CD18 ligand that is also thought to bind the I domain of CD11b. In contrast, rNIF does not appear to block the binding of factor X to CD11b/CD18 on neutrophils. These results suggest that CD11b/CD18 has multiple distinct binding sites for its cognate ligands, including, but not limited to, the I domain. NIF interferes with the binding of a subset of these CD11b/CD18 ligands in a highly selective manner.
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PMID:Functional interaction between the integrin antagonist neutrophil inhibitory factor and the I domain of CD11b/CD18. 792 63

The crystal structure of class Pi glutathione S-transferase from porcine lung (pGST P1-1) in complex with glutathione sulphonate has been refined at 2.11 A resolution, to a crystallographic R-factor of 16.5% for 21, 165 unique reflections. The refined structure includes 3314 protein atoms, 46 inhibitor (glutathione sulphonate) atoms and 254 water molecules. The model shows good stereochemistry, with root-mean-square deviations from ideal bond lengths and bond angles of 0.011 A and 2.8 degrees, respectively. The estimated root-mean-square co-ordinate error is 0.2 A. The protein is a dimer assembled from identical subunits of 207 amino acid residues. The tertiary structure of the pGST P1 subunit is organized as two domains, the N-terminal domain (domain I, residues 1 to 74) and the larger C-terminal domain (domain II, residues 81 to 207). Glutathione sulphonate, a competitive inhibitor, binds to the G-site region (i.e. the glutathione-binding region) of the active site located on each subunit. Each G-site is, however, structurally dependent of the neighbouring subunit as structural elements forming a fully functional G-site are provided by both subunits, with domain I as the major supporting framework. A number of direct and water-mediated polar interactions are involved in sequestering the glutathione analogue at the G-site. The extended conformation assumed by the enzyme-bound inhibitor as well as the strategic interactions between inhibitor and protein, closely resemble those observed for the physiological substrate, reduced glutathione bound at the active site of class Mu glutathione S-transferase 3-3. Hydrogen bonding between the sulphonyl moiety of the inhibitor and the hydroxyl group of an evolutionary conserved tyrosine residue, Tyr7, provides the first direct structural evidence for a catalytic protein group in glutathione S-transferases that is involved in the activation of the substrate glutathione. The catalytic role for Tyr7 has subsequently been confirmed by mutagenesis and kinetic studies. Comparison of the known crystal structures for class Pi, class Mu and class Alpha isoenzymes, indicates that the cytosolic glutathione S-transferases share a common fold and that the structural features for catalysis are similar.
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PMID:Refined crystal structure of porcine class Pi glutathione S-transferase (pGST P1-1) at 2.1 A resolution. 793 43

The activities of enzymes related to glutathione synthesis, degradation, and function were analyzed in various brain regions (cerebral cortex, caudate nucleus, putamen, globus pallidus, and substantia nigra) from patients dying with pathologically proven Parkinson's disease (PD) and multiple system atrophy (MSA), and from matched controls with no neurological disorder. The activity of the glutathione degradative enzyme, gamma-glutamyltranspeptidase, was selectively elevated in substantia nigra (SN) in PD. In contrast, the activity of the synthetic enzyme, gamma-glutamylcysteine synthetase, was unaltered in SN and other brain areas in PD. Similarly, glutathione peroxidase and glutathione transferase activities were unaltered in SN or in other brain regions in PD. gamma-Glutamylcysteine synthetase, gamma-glutamyltranspeptidase, glutathione peroxidase, and glutathione transferase activities were normal in SN and most other brain areas in MSA. However, glutathione peroxidase activity was increased in the lateral globus pallidus and caudate nucleus in MSA. The depletion of reduced glutathione (GSH) in the SN in PD, with no change in oxidized glutathione (GSSG), may be due to efflux of GSH mainly out of glia promoted by gamma-glutamyltranspeptidase, perhaps with additional increased conversion of GSH to GSSG (which itself is transported out of cells by gamma-glutamyltranspeptidase), in response to increased hydrogen peroxide formation.
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PMID:Glutathione-related enzymes in brain in Parkinson's disease. 808 Feb 39

Arsenite is a potent toxin, a carcinogen, and an inducer of heat shock proteins. In this study we found that arsenite is also a novel inducer of NAD(P)H:quinone acceptor oxidoreductase (QOR) [EC 1.6.99.2] in both liver and kidney. The increases in activity were unlinked to those caused by prior treatment with the polyaromatic hydrocarbon inducer, beta-naphthoflavone suggesting different mechanisms of induction. A single dose of sodium arsenite (75 mumol/kg sc) caused a 4-fold and 2-fold increase in activity in kidney and liver, respectively, whereas beta-naphthoflavone (60 mg/kg ip once daily for 4 days) caused a 10-fold and 4.7-fold increase in kidney and liver, respectively. This is the first study of a metalloid inducing QOR activity. Arsenite is chemically unlike any other inducer described for QOR, which include phenolic antioxidants and Michael acceptors, polyaromatic hydrocarbons, and hydrogen peroxide. Arsenite also increased glutathione S-transferase [EC 2.5.1.18] activity in rat kidney. Arsenite could be inducing QOR in liver and kidney and the glutathione S-transferase activity in kidney by an oxidant stress mechanism.
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PMID:Effects of arsenite treatment on NAD(P)H:quinone acceptor oxidoreductase activity in liver, lung, kidney, and heart of the rat. Comparison to induction by the polyaromatic hydrocarbon, beta-naphthoflavone. 809 5

The determination of the nuclear magnetic resonance (NMR) solution structured of the mixed disulfide between the mutant Escherichia coli glutaredoxin Grx(C14S) and glutathione (GSH), Grx(C14S)-SG, is described, the binding site for GSH on Grx(C14S) is located, and the non-bonding interactions between -SG and the protein are characterized. Based on nearly complete sequence-specific NMR assignments, 1010 nuclear Overhauser enhancement upper distance constraints and 116 dihedral angle constraints were obtained as the input for the structure calculations, for which the distance geometry program DIANA was used followed by energy minimization in a waterbath with the AMBER force field in the program OPAL. The -SG moiety was found to be localized on the surface of the protein in a cleft bounded by the amino acid residues Y13, T58, V59, Y72, T73 and D74. Hydrogen bonds have been identified between -SG and the residues V59 and T73 of Grx(C14S), and the formation of an additional hydrogen bond with Y72 and electrostatic interactions with the side-chains of D74 and K45 are also compatible with the NMR conformational constraints. Comparison of the reduced and oxidized forms of Grx with Grx(C14S)-SG shows that the mixed disulfide more closely resembles the oxidized form of the protein. Functional implications of this observation are discussed. Comparisons are also made with the related proteins bacteriophage T4 glutaredoxin and glutathione S-transferase.
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PMID:The nuclear magnetic resonance solution structure of the mixed disulfide between Escherichia coli glutaredoxin(C14S) and glutathione. 810 93

Using transfection and gel retardation assays, we have characterized further the antioxidant response element (ARE) found in the 5'-flanking region of the rat glutathione S-transferase Ya subunit gene. The ARE core sequence (5'-GTGACAAAGC-3') is sufficient for transcriptional activation of the Ya subunit gene by metabolizable planar aromatic compounds, phenolic antioxidants, and hydrogen peroxide. When the ARE sequence is ligated to a chloramphenicol acetyltransferase reporter gene and transfected into HepG2 cells, chloramphenicol acetyltransferase activity is modestly inducible by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). Since the ARE is responsive to TPA and shows some sequence similarity to an AP-1-binding site (Jun/Fos recognition motif), we have explored whether members of the Jun/Fos family of transcription factors might bind to the ARE. Using in vitro synthesized Jun and Fos, binding to the ARE could not be detected, whereas Jun/Fos binding to a classical AP-1-binding site, a TPA response element (TRE) from the human collagenase gene, could be demonstrated by gel retardation assays. If the 2 A nucleotides underlined in the ARE core sequence (5'-GTGACAAAGC-3') are changed to TC, the ARE sequence (ARE-TRE) becomes a high-affinity AP-1-binding site and retains xenobiotic inducibility. Removal of the -GC- dinucleotide at the 3'-end of the ARE or the ARE-TRE eliminates xenobiotic inducibility. However, the ARE-TRE construct without the -GC- dinucleotide is still a high-affinity AP-1 site and responsive to TPA. Taken together, our data suggest that the ARE is not a high-affinity binding site for the Jun/Fos heterodimer. Functionally, however, an AP-1-binding site can resemble an ARE in its response to various xenobiotics if a 3'-GC- dinucleotide is present.
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PMID:Transcriptional regulation of a rat liver glutathione S-transferase Ya subunit gene. Analysis of the antioxidant response element and its activation by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate. 817 1

To clarify the mechanism of oxidative stress in skeletal muscle atrophied by immobilization, we measured the activities of antioxidant enzymes and xanthine oxidase (XOD) and carried out the cytochemical study of hydrogen peroxide in a typical slow red muscle, the soleus. Male Wistar rats (15 wk old), of which ankle joints of one hindlimb were immobilized in the fully extended position, were killed after 4, 8, or 12 days. The activities of Mn-containing superoxide dismutase (Mn-SOD), Cu-Zn-containing superoxide dismutase (Cu-Zn-SOD), Se-dependent glutathione peroxidase (Se-GSHPx), glutathione S-transferase, catalase, and glutathione reductase were measured spectrophotometrically. The XOD activity and the concentrations of hypoxanthine, xanthine, and urate were measured using a high-performance liquid chromatography. The cytochemical study of hydrogen peroxide in short-term organ culture was performed using an electron microscope. Increased Cu-Zn-SOD and decreased Mn-SOD in atrophy might reflect increased generation of superoxide anions in the cytoplasm rather than in the mitochondria. The source of superoxide anions in the cytoplasm might be the increased superoxide-producing XOD. Enhanced generation of superoxide anions and increased Cu-Zn-SOD activity in atrophy suggested the enhanced generation of hydrogen peroxide in the cytoplasm. Due to the unchanged activity of Se-GSHPx and the unchanged or slightly increased activity of catalase in atrophy, the ability to degrade hydrogen peroxide might not increase so much. Hence, hydrogen peroxide is expected to be increased in atrophy. The cytochemical study supported this expectation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mechanism of oxidative stress in skeletal muscle atrophied by immobilization. 827 38

Glutathione peroxidase was purified from the total membrane fractions of a yeast, Hansenula mrakii IFO 0895. The purified enzyme gave a single protein band with a molecular mass of 28 kDa on SDS-PAGE. The enzyme showed activity to various lipid hydroperoxides and their methyl esters. The enzyme was also active toward phosphatidylcholine hydroperoxide and cholesterol hydroperoxide. Since the enzyme was not active on hydrogen peroxide, the enzyme was thought to be a kind of glutathione S-transferase, although the purified enzyme did not show the glutathione-conjugating activity with electrophilic compounds such as 1-chloro-2,4-dinitrobenzene and o-dinitrobenzene, which are used as the substrate of glutathione S-transferase in yeast. The glutathione peroxidase in H. mrakii was then suggested to be a novel type of glutathione peroxidase in substrate specificity and intracellular localization, being different from those of other sources purified so far.
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PMID:Oxidative stress response in yeast: purification and some properties of a membrane-bound glutathione peroxidase from Hansenula mrakii. 832 47

The rat alpha 1-1 glutathione S-transferase (GST) contains a single, non-essential tryptophan and only 8 tyrosines in each subunit. One of these tyrosines, Tyr-9, hydrogen bonds to the substrate glutathione and stabilizes the nucleophilic thiolate anion. Two mutant proteins that allow for the spectrocopic determination of the pKa of this catalytic residue have been constructed. The W21F mutant provides a fully active GST with no tryptophans, and the double mutant W21F/Y9F lacks both tryptophan and the active site tyrosine. The intrinsic fluorescence and absorbance properties of these mutants are dominated by tyrosine. Fluorescence emission, fluorescence excitation, and absorbance spectral changes of samples containing the W21F mutant at several pH values in the range 6.8-9.0 reveal a pH-dependent increase in the contribution of tyrosinate. No spectral changes are observed with the W21F/Y9F protein in this pH range. At pH 12.5, both proteins exhibit complete deprotonation of all tyrosines. The pKa of Tyr-9 determined from these spectroscopic changes is 8.3-8.5. The changes in absorbance at 250 and 295 nm correspond to titration of 0.95 +/- 0.29 tyrosines/subunit in the W21F protein between pH 6.9 and 9.3. Moreover, addition of the inhibitor S-hexylglutathione results in an apparent increase in the pKa of Tyr-9. Together, these results indicate that the catalytically active Tyr of GSTs has a pKa value that is 1.8-2.0 pKa units below tyrosine in solution. It is likely that this decrease in the pKa of Tyr-9 contributes to catalysis by altering the equilibrium position of the proton shared between Tyr-9 and GSH, and this active site residue may function as a general base catalyst in addition to a hydrogen bond donor.
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PMID:The catalytic mechanism of glutathione S-transferase (GST). Spectroscopic determination of the pKa of Tyr-9 in rat alpha 1-1 GST. 836 71


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