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PubMed1986

Isoenzyme patterns of glutathione transferases from mammalian erythrocytes.

The occurrence of glutathione transferase isoenzymes in mammalian erythrocytes was investigated. The enzymes present in the hemolysates of human, horse, beef, pig, and sheep erythrocytes were purified by a column of GSH-linked epoxy-activated Sepharose 6B and subjected to an isoelectric focusing run in the pH range 3.5-10. Human and horse preparations were resolved in a single peak of activity centered at pH 4.6 and 5.9, respectively. Two forms with a maximum of activity at pH 4.9 and 7.0 and four with a maximum at pH 5.9, 6.5, 7.1, and 8.1 were separated from bovine and porcine erythrocytes. At least six forms ranging from pH 4.3 to pH 7.1 were present in the ovine preparation, the neutral contributing more than 90% of total activity. The subunit composition of affinity-bound fractions was studied by sodium dodecyl sulfate-gel electrophoresis. The analysis revealed that erythrocyte glutathione transferases are composed of subunits of identical molecular weights. This result suggests that the polymorphism existing in beef, pig, and sheep may be due to charge isomers. The erythrocyte glutathione transferases did not express selenium-independent GSH peroxidase activity.

Animals↗
PubMed1988

Interaction of organic azides with purified camel glutathione S-transferase.

A series of organic azides was synthesized and was tested as inhibitors of purified camel glutathione S-transferases. Enzymes purified from camel liver, lung, and kidney were inhibited reversibly by these compounds in a concentration-dependent pattern. The liver glutathione S-transferase was more sensitive to inhibition by most of these compounds and the lung enzyme was the least affected. The most effective reversible inhibitors of the tested organic azides for the purified camel liver enzyme were alkyl and allyl azides. The inhibition occurred immediately upon adding the inhibitors and remained constant during a further 30-min incubation period. The tested organic azides were found to inhibit the glutathione S-transferase catalyzed conjugation of glutathione with both 1-chloro-2,4-dinitrobenzene and 4-nitrobenzyl chloride and the kinetics of these inhibitions was qualitatively different, being competitive with some inhibitors and noncompetitive with others.

Animals↗
PubMed2005

Thermodynamic properties of oxidoreductase, transferase, hydrolase, and ligase reactions.

Transferases formally couple together two oxidoreductase reactions or two hydrolase reactions. Therefore the thermodynamic properties of transferase reactions can be calculated from differences between thermodynamic properties of two oxidoreductase or two hydrolase reactions. Ligases couple together two hydrolase reactions, and so their thermodynamic properties can be calculated from differences between two hydrolase reactions. These relationships are demonstrated by calculating standard transformed Gibbs energies of reaction and the changes in binding of hydrogen ions at pHs 5-9 of a number of oxidoreductase, transferase, hydrolase, and ligase reactions by use of the data base BasicBiochemData2 and its recent extensions. Coupling is not restricted to two reactions, and an example is given of the coupling of three reactions.

Hydrogen-Ion Concentration↗
PubMed2004

Seasonal variations in antioxidant defences in blue mussels Mytilus edulis collected from a polluted area: major contributions in gills of an inducible isoform of Cu/Zn-superoxide dismutase and of glutathione S-transferase.

In the present work, we investigated in the blue mussel (Mytilus edulis) the seasonal variations in the activity of several enzymes, which participate in the cellular defence system that is involved in the adaptive response of organisms to pollution. The activity levels of glutathione S-transferase, glutathione peroxidase, glutathione reductase and three isoforms of Cu/Zn-superoxide dismutase in gills and digestive glands of this bivalve species were used as biomarkers. Adult wild mussels were collected in Le Havre harbour (north-west coast of France) from four sites with different environmental conditions. Measurements of enzymatic activities were performed on tissue homogenates except for Cu/Zn-superoxide dismutase for which the activity of each isoform was detected on gel after isoelectric focusing. Seasonal variations in antioxidant enzyme activities were observed, characterized by low activity levels during winter, a period where oxidative stress is known to be high in bivalves. A clear-cut discrepancy between tissues was noted concerning inter-individual variability of data, which was low in gills but high in digestive gland, leading to the conclusion that gills could preferentially be used in biomonitoring studies dealing with oxidative stress in the blue mussel. As compared to animals from the reference site, mussels from the most polluted sites exhibited changes in the Cu/Zn-superoxide dismutase pattern characterized by an increase in the activity of the more acidic isoform without significant variation of the total activity of the enzyme. The most striking data were recorded in mussels collected at the outlet of a thermoelectric power plant. When compared to animals from the reference site, not only their gills showed a highly significant induction of the most acidic isoform of the Cu/Zn-superoxide dismutase (+340%, P < 0.001) but also high levels of glutathione S-transferase activity (+269%, P < 0.001). This study points out the usefulness of Cu/Zn-superoxide dismutase expression pattern as a biomarker of exposure to environmental stress rather than measurement of total activity of the enzyme, in field studies using Mytilus edulis. It also indicates the informative potential for glutathione S-transferase measurements in gills and underlines the advantages of selecting a battery of biomarkers for evaluating the impact of contamination on marine organisms.

Analysis of Variance↗
PubMed1995

Glutathione s-transferase genotypes as risk factors for head and neck cancer.

BACKGROUND: Several enzymatic systems, including glutathione S-transferases, are involved in the metabolism of environmental agents. The absence of glutathione S-transferases mu (GSTM1) and theta (GSTT1) results in decreased detoxification of carcinogens, for example, chemicals in cigarette smoke. These metabolic deficiencies may predispose individuals to the development of smoking-related tumors, such as cancers of the lung, head and neck, and bladder. METHODS: The glutathione S-transferase genotypes of 186 previously untreated patients with squamous cell carcinoma of the head and neck and 42 healthy controls were determined with polymerase chain reaction (PCR) methodologies. Lymphocytes separated from heparinized peripheral blood or whole blood extracts served as sources of genomic DNA. The presence or absence of the gene-specific PCR products revealed the positive or negative genotypes, respectively. RESULTS: The absence of the GSTM1 genotype conferred an odds ratio of 2.37, and the 95% confidence interval (CI) was 1.20 to 4.67. The absence of the GSTT1 gene conferred an odds ratio of 1.47 (CI 0.71 to 3.02). In the population of 42 patients and their matched 42 controls, the absence of the GSTM1 and GSTT1 genotypes conferred odds ratios of 3.10 (CI 1.24 to 7.75) and 2.18 (CI 0.91 to 5.23), respectively. CONCLUSIONS: Despite the small study size, our preliminary data suggest that genetically determined factors of carcinogen metabolism may be associated with increased risk for head and neck cancer.

Base Composition↗
PubMed1984

Irreversible inhibition of hepatic glutathione S-transferase by ciprofibrate, a peroxisome proliferator.

Ciprofibrate (2-[4-(2,2-dichlorocyclopropyl) phenoxy]2-methyl propionic acid) which is a hypolipidemic agent and has been shown to cause peroxisome proliferation, non-competitively inhibits glutathione S-transferase activity of rat liver, both in vivo and in vitro. Among all the glutathione S-transferases of rat liver, ligandin is maximally inhibited by ciprofibrate. Studies with the purified glutathione S-transferases of rat liver indicate that the affinities of different subunits of liver enzymes for ciprofibrate are in the order Ya greater than Yb, Yb' greater than Yc.

Animals↗
PubMed1998

Regulation of rat glutathione S-transferase A5 by cancer chemopreventive agents: mechanisms of inducible resistance to aflatoxin B1.

The rat can be protected against aflatoxin B1 (AFB1) hepatocarcinogenesis by being fed on a diet containing the synthetic antioxidant ethoxyquin. Evidence suggests that chemoprotection against AFB1 is due to increased detoxification of the mycotoxin by one or more inducible drug-metabolising enzymes. The glutathione S-transferase (GST) isoenzymes in rat liver that contribute to ethoxyquin-induced chemoprotection against AFB1 have been identified by protein purification. This approach resulted in the isolation of several heterodimeric class alpha GST, all of which contained the A5 subunit and possessed at least 50-fold greater activity towards AFB1-8,9-epoxide than previously studied transferases. Molecular cloning and heterologous expression of rat GSTA5-5 has led to the demonstration that it exhibits substantially greater activity for AFB1-8,9-epoxide than other rat transferases. The A5 homodimer can also catalyse the conjugation of glutathione with other epoxides, such as trans-stilbene oxide and 1,2-epoxy-3-(4'-nitrophenoxy)propane, and possesses high catalytic activity for the reactive aldehyde 4-hydroxynonenal. Western blotting has shown that the A5 subunit is not only induced by ethoxyquin but that it is also induced by other cancer chemopreventive agents, such as butylated hydroxyanisole, oltipraz, benzyl isothiocyanate, indole-3-carbinol and coumarin. In addition to GSTA5, we have identified a novel aflatoxin-aldehyde reductase (AFAR) that is similarly induced by ethoxyquin. However, immunoblotting has shown that GSTA5 and AFAR are not always co-ordinately regulated by chemoprotectors. In order to gain a better understanding of the mechanisms responsible for the induction of GSTA5 protein, the GSTA5 gene has been cloned. It was isolated on two overlapping bacteriophage lambda clones and found to be approximately 12 kb in length. The transcriptional start site of GSTA5 has been identified 228 bp upstream from the ATG translational initiation codon. Computer-assisted analysis of the upstream sequence has indicated the presence of a putative antioxidant responsive element (located between -421 and -429 bp) which may be responsible for the induction of GSTA5 by chemopreventive agents.

Aflatoxin B1↗
PubMed1998

Glutathione S-transferase polymorphisms: influence on susceptibility to cancer.

The glutathione S-transferase supergene family includes several loci that demonstrate well characterised polymorphisms. The apparently critical role of these enzymes in cellular protection from the cytotoxic and mutagenic effects of electrophiles suggest that alleles associated with impaired detoxification will confer an increased susceptibility to a wide range of diseases. This hypothesis has been examined in case control studies and while data in some diseases such as lung cancer are conflicting, an increasing body of evidence suggests the importance of several glutathione S-transferase polymorphisms. In particular, GST genotypes have been associated with an increased susceptibility or worse outcome in diseases associated with oxidative stress. For example, both GSTM1 and GSTT1 genotypes are associated with susceptibility and outcome in cutaneous basal cell carcinoma. It still remains unclear however, why particular glutathione S-transferase loci are associated with altered risk in some diseases but not others. Further, the true in vivo substrates of these enzymes is unknown, consequently their mechanism of action remains unclear.

Alleles↗
PubMed1998

Site-directed mutagenesis of the Proteus mirabilis glutathione transferase B1-1 G-site.

In order to investigate the roles of near N-terminus Tyr, Cys, and Ser residues in the activity of bacterial glutathione transferase (GSTB1-1) site-directed mutagenesis was used to replace the following residues: Tyr-4, Tyr-5, Ser-9, Cys-10, Ser-11, and Ser-13. The results presented here show that, unlike all other alpha, mu, pi, theta and sigma classes of glutathione transferases so far investigated, GSTB1-1 does not utilise any Tyr, Ser or Cys residue to activate glutathione. These results also suggest that the bacterial glutathione transferases may require classification into their own class.

Bacterial Proteins↗
PubMed2002

Structure of the ecto-ADP-ribosyl transferase ART2.2 from rat.

The mammalian extracellular ADP-ribosyl transferases ART1 through ART5 are sequence-related to each other. Among them ART2 is involved in immuno regulation. The variant ART2.2 was expressed in the periplasm of Escherichia coli and crystallized. Its structure was determined by X-ray diffraction at 1.7A resolution in one crystal form and at slightly lower resolutions in two others. The active center was indicated by a ligated nicotinamide analogue, which also revealed a small induced-fit. The centerpiece of the chainfold of ART2.2 agrees with those of all bacterial ADP-ribosyl transferases. This correspondence and the nicotinamide position were used to model the binding structure of the whole substrate NAD(+) at ART2.2. Two of the bacterial enzymes are structurally more closely related to ART2.2 while the others are more closely related to the eukaryotic poly(ADP-ribosyl)polymerase. This splits the ADP-ribosyl transferases into two distinct subfamilies. A special feature of ART2.2 is its long N-terminal extension and two disulfide bridges that are far away from the active center. They stabilize the protein against denaturation and presumably also against shearing forces parallel with the membrane where ART2.2 is anchored.

ADP Ribose Transferases↗
PubMed2000

Quantitative and qualitative gender-related differences in jejunal glutathione S-transferase in the rat effect of testosterone administration.

Gender-related differences and the regulation by testosterone of glutathione S-transferase were studied in rat jejunum. We analyzed enzyme activity and the relative content of GST subunits. Four experimental groups of adult rats were studied: normal males, castrated males, castrated males injected with testosterone and normal females. Glutathione S-transferase activity was assayed using 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene as substrates. Differences in subunit composition among groups were evaluated by western blot analysis. The results demonstrated that 1-chloro-2,4-dinitrobenzene conjugation rate is higher in normal males than in normal females and castrated males. Testosterone administration to castrated males raised the activity up to the level observed in normal males. No significant difference in glutathione S-transferase activity towards 1,2-dichloro-4-nitrobenzene was observed among groups. Western blot analysis revealed that males and females differ in all subunits tested that is, rGSTA2, rGSTM1, rGSTM2 and rGSTP1, and that testosterone regulates the content of rGSTM1, rGSTM2 and rGSTP1. In conclusion, jejunal GST shows a gender-dependent regulation affecting both enzyme activity and subunit composition, and testosterone appears to be one of the factors involved.

Animals↗
PubMed2000

Capacity of mercury volatilization by mer (from Escherichia coli) and glutathione S-transferase (from Schistosoma mansoni) genes cloned in Escherichia coli.

A study was carried out to evaluate the capacity for mercury volatilization by genetically engineered strains that express the mer and glutathione S-transferase genes from Escherichia coli and Schistosoma mansoni, respectively. This method enabled strains containing simultaneously mer and glutathione S-transferase genes to grow in high concentrations of mercuric chloride (30 microg/ml) and to volatilize part of the mercury (248 microg/g cell dry wt.) present in the culture medium, while strains bearing only a single gene, did not have the same behavior. Up to 70% of the total mercury of bacterial volatilization occurred in the first 4 h. Although the findings were preliminary, the genetically engineered strain containing simultaneously the mer and glutathione S-transferase genes show a great potential for bioremediation. It may be used in a closed system to remove by volatilization, and recover mercury (Hg0) from contaminated effluents, such as industrial effluent, for instance.

Animals↗
PubMedDate not supplied

Glutathione-S-transferase activity from rat placenta.

Glutathione S-transferase activity significantly decreased in the rat placenta from the 16th to the 20th day of gestation. Isoelectric focusing of rat placenta supernatant yielded essentially a single peak of glutathione S-transferase activity with I-chloro-2,4-dinitrobenzene as substrate, centred on pH 7.45. Substrate specificity measurements, as well as inhibitory studies, revealed pronounced differences between rat and human placental enzymes. Whether the biochemical differences between rat and human GSH-Trs are reflected in physiological differences remains to be ascertained. The sodium dodecyl sulphate (SDS) gel electrophoresis data on subunit composition showed that the rat enzyme is composed of two identical subunits whose molecular mass closely approaches that of human transferase.

Animals↗
PubMed2002

Damaged interlobular bile ducts in primary biliary cirrhosis show reduced expression of glutathione-S-transferase-pi and aberrant expression of 4-hydroxynonenal.

BACKGROUND/AIMS: Chronic inflammation induces oxidative stress by producing reactive oxygen species. We investigated how the oxidative stress associated with chronic cholangitis induce bile duct damages in primary biliary cirrhosis. METHODS: The intracellular status of lipid peroxidation due to oxidative stress and that of glutathione, an endogenous cytoprotective molecule, were examined in primary biliary cirrhosis and controls by immunostaining of 4-hydroxynonenal and glutathione-S-transferase-pi. The former is a by-product of lipid peroxidation, and the latter is involved in the formation of intracellular glutathione. RESULTS: In the damaged bile ducts of primary biliary cirrhosis, glutathione-S-transferase-pi expression was markedly reduced, reflecting reduction of intracellular glutathione, and perinuclear expression of 4-hydroxynonenal was frequent, reflecting active lipid peroxidation associated with biliary epithelial damages. There was diffuse/luminal expression of 4-hydroxynonenal in the bile ducts frequent in primary biliary cirrhosis and controls, likely reflecting absorption of 4-hydroxynonenal, also a component of oxidized low-density lipoprotein, from bile via scavenger receptor class B type 1 on biliary epithelium. CONCLUSIONS: The data suggest that lipid peroxidation in the bile ducts with reduced expression of glutathione-S-transferase-pi, may be an important pathologic process leading to the bile duct damage of primary biliary cirrhosis.

Aldehydes↗
PubMed2001

Characterisation of polymeric surfactants that are glutathione transferase mimics.

Catalysts that can detoxify reactive organic chemicals (electrophiles) could be of potential beneficial use. Electrophilic compounds are common toxic agents that are conjugated to endogenous nucleophiles (i.e. glutathione) in an enzyme catalysed reaction (by glutathione transferases). Here, the properties of newly synthesised polymeric surfactant catalysts, which are glutathione transferase mimics, are described (which are not limited to the glutathione thiol donor). Reactions studied were nucleophilic aromatic substitution with 1-chloro-2,4-dinitrobenzene (CDNB) and thiolysis of p-nitrophenyl acetate. Polymeric quaternary ammonium salts synthesised starting from 2-(dimethyl-amino)ethylmethacrylate or 1,3-bis(dimethylamino)isopropylmethacrylate were used as surfactants. Five polysoaps were studied possessing different charge density and different density of hydrophobic chains. In comparison with cetyltrimethylammonium bromide, the polymeric surfactants were clearly more efficient catalysts (i.e. 4.9 vs. 150 (10(3) per M(2)/s) with benzyl hydrosulfide and CDNB). Polymers with high charge and hydrophobic density were most efficient. With a given catalyst, increasing hydrophobicity of the thiol substrate parallels increasing reaction rates (e.g. 0.7- > or = 37 (10(3) per M(2)/s) with CDNB). Concentration of the substrate in the micellar pseudophase together with solvent shielding is suggested as the underlying rate enhancement mechanism. Dead-end Meisenheimer complex stabilisation, where an extremely electrophilic compound (1,3,5-trinitrobenzene) reversibly interacts with glutathione is seen both with glutathione transferases and the polymeric surfactant catalysts. The degree of stabilisation follows catalytic efficiency and thus supports the above structure activity relationships. In conclusion, polymeric materials that can perform biological functions in detoxication are described, as well as their optimal properties.

Catalysis↗
PubMed1982

High-performance liquid chromatographic assay of cytosolic glutathione S-transferase activity with styrene oxide.

A high-performance liquid chromatographic (HPLC) assay for measuring cytosolic glutathione S-transferase activity with styrene oxide is described. After incubating lung or liver cytosol with reduced glutathione and styrene oxide, unreacted styrene oxide is extracted into ethyl acetate. An aliquot of the aqueous phase is evaporated to dryness and reconstituted in the mobile phase for HPLC analysis. The two glutathione conjugates of styrene oxide [S-(1-phenyl-2-hydroxyethyl)glutathione and S-(2-phenyl-2-hydroxyethyl)glutathione] are separated in less than 10 min; quantitation of transferase activity is based on the comparison of the UV absorbance of the two conjugates at 254 nm with synthetic conjugate standards. As little as 1 nmole of either conjugate can be quantitated with good precision. This assay has advantages over previously published methods for measuring styrene oxide glutathione S-transferase activity as it does not depend on the use of relatively unstable and expensive radiolabelled substrates.

Animals↗
PubMed1999

Activity of glutathione transferase and reductase in tissues of bird cherry-oat aphid during its host-plant alternation.

Changes in activity of detoxifying enzymes, involved in metabolism of glutathione in bird cherry-oat aphid during its host alternation have been investigated. Glutathione transferase (GST) and glutathione reductase (GR) activity was found in homogenates from tissues of the bird cherry-oat aphid, Rhopalosiphum padi (L.). The highest activity of the enzymes was recorded in winged migrants that fly from bird cherry (Prunus padus L.), the winter host onto cereals a summer host. Before the migration an increase in activity of the glutathione transferase and glutathione reductase within tissues of winged migrants was observed. When the migrants started to feed on cereals, GST activity further increased and GR activity decreased. The significance of the R. padi glutathione transferase and reductase in detoxification of plant allelochemicals while the aphid host-plants alternation is discussed.

Animals↗
PubMed2002

The synthesis and biological evaluation of a series of potent dual inhibitors of farnesyl and geranyl-Geranyl protein transferases.

We have prepared a series of potent, dual inhibitors of the prenyl transferases farnesyl protein transferase (FPTase) and geranyl-geranyl protein transferase I (GGPTase). The compounds were shown to possess potent activity against both enzymes in cell culture. Mechanistic analysis has shown that the compounds are CAAX competitive for FPTase inhibition but geranyl-geranyl pyrophosphate (GGPP) competitive for GGPTase inhibiton.

Alkyl and Aryl Transferases↗