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

---

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 investigated the role of a glutathione S-transferase (GST) with inherent peroxidase activity in the cellular defense against lipid peroxidation and free radical-mediated oxidative damage. Stable transfectants of human T47D cells were generated which express recombinant rat GST-Yc from a human cytomegalovirus promoter-based expression vector. Among several GST-Yc transfectants characterized, two of them contained, respectively, 2- and 3-fold higher GST activity than parental cells or control transfectants and, respectively, 4-5- and 8-10-fold higher selenium-independent glutathione peroxidase activity. Cellular growth kinetics and rates of [3H]thymidine incorporation showed that both transfectants were more resistant to oxidative shocks mediated by cumene hydroperoxide or singlet oxygen generated by photosensitized rose bengal than were T47D cells and control transfectants. In contrast, a T47D transfectant, which expressed high levels of recombinant selenoglutathione peroxidase and showed enhanced resistance to cumene hydroperoxide (Mirault, M.-E., Tremblay, A., Beaudoin, N., and Tremblay, M. J. (1991) J. Biol. Chem. 266, 20752-20760), was as sensitive as parental cells to singlet oxygen. No difference was found in growth sensitivity to 1-h shock treatments with the quinonoid drug daunomycin, irrespective of GST-Yc or selenoglutathione peroxidase overexpression in these cells.
...
PMID:Distinct oxidoresistance phenotype of human T47D cells transfected by rat glutathione S-transferase Yc expression vectors. 174 Apr 15

The activity of glutathione S-transferase (GST) decreased progressively in Schistosoma mansoni from mice treated with oltipraz (OPZ). However, the peroxidase activity of GST (selenium-independent) and selenium-dependent glutathione peroxidase was not affected by OPZ treatment. Purification and quantification of GST from worms after OPZ treatment indicated that the decrease in enzyme activity was greater than could be accounted for by the decrease in GST protein content. SDS-polyacrylamide gel electrophoresis followed by Western blot analysis with GST isoenzyme specific antisera revealed a slight decrease in the quantity of both 26 and 28 kDa GSTs. Fractionation of cytosolic GSTs from male S. mansoni by chromatofocusing resolved three major isoenzymes (SmI, II and III) and a minor form which eluted first from the column. SmI, II and III all had a molecular weight of about 28 kDa on SDS-polyacrylamide gel electrophoresis. However, on electrophoresis in the absence of SDS, the three GST forms exhibited different mobilities. The pattern of SmI, II and III was similar in untreated and OPZ-treated worms, but the activities of the isoenzymes from treated worms were lower. The results suggest that OPZ interacts with the GST isoenzymes SmI, II and III in a similar manner; thus, the effects are not isoenzyme specific. Taken together, these results suggest that OPZ and/or its metabolites interact directly with GST resulting in inhibition of activity and reduction in total enzyme protein. This mechanism may be important in the antischistosomal action of OPZ.
...
PMID:Oltipraz-induced decrease in the activity of cytosolic glutathione S-transferase in Schistosoma mansoni. 178 33

Contribution of various hemoproteins to peroxidase oxidation of benzidine and its derivatives as well as effects of these substances on functional state of hepatocytes are discussed. Benzidine and its derivatives were shown to induce those forms of cytochrome P-450 which were involved in accelerated oxidation of the carcinogenic drugs studied as well as affected the glutathione transferase, NADPH-dependent glutathione reductase activities and the activity of antioxidant system enzymes. Increase in content of cytochrome P-450, glutathione-dependent enzymes and other effects specific for adult hepatocytes, which occurred in presence of aminobiphenyls, were accompanied by decrease in content of receptors to epidermal factor of growth regulating the hepatocytes proliferation.
...
PMID:[The role of carcinogenic aminobiphenyls in hepatocyte differentiation]. 181 15

Human muscle glutathione S-transferase isozyme, GST zeta (pI 5.2) has been purified by three different methods using immunoaffinity chromatography, DEAE cellulose chromatography, and isoelectric focusing. GST zeta prepared by any of the three methods does not recognize antibodies raised against the alpha, mu, or pi class glutathione S-transferases of human tissues. GST zeta has a blocked N-terminus and its peptide fingerprints also indicate it to be distinct from the alpha, mu, or pi class isozymes. As compared to GSTs of alpha, mu, and pi classes, GST zeta displays higher activities toward t-stilbene oxide and Leukotriene A4 methyl ester. GST zeta also expresses GSH-peroxidase activity toward hydrogen peroxide. The Kms of GST zeta for CDNB and GSH were comparable to those reported for other human GSTs but its Vmax for CDNB, 7620 mol/mol/min, was found to be considerably higher than that reported for other human GSTs. The kinetics of inhibition of GST zeta by hematin, bile acids, and other inhibitors also indicate that it was distinct from the three classes of GST isozymes. These studies suggest that GST zeta corresponds to a locus distinct from GST1, GST2, and GST3 and probably corresponds to the GST4 locus as suggested previously by Laisney et al. (1984, Human Genet. 68, 221-227). The results of peptide fingerprints and kinetic analysis indicate that as compared to the pi and alpha class isozymes, GST zeta has more structural and functional similarities with the mu class isozymes. Besides GST zeta several other GST isozymes belonging to pi and mu class have also been characterized in muscle. The pi class GST isozymes of muscle have considerable charge heterogeneity among them despite identical N-terminal sequences.
...
PMID:Purification and characterization of human muscle glutathione S-transferases: evidence that glutathione S-transferase zeta corresponds to a locus distinct from GST1, GST2, and GST3. 184 34

The present studies were undertaken to elucidate the mechanism(s) of the anti-neoplastic effect of diallyl sulfide (allyl sulfide, DAS), a naturally occurring organosulfide abundant in vegetables of the Allium genus, against benzo[a]pyrene (B[a]P)-induced carcinogenesis in the mouse. DAS treatment caused a significant increase in glutathione S-transferase (GST) activity, an enzyme system responsible for detoxification of a variety of electrophilic xenobiotics including several harmful B[a]P metabolites, of mouse stomach in a dose-dependent manner. This activity in the stomach of mice treated with 25, 50 and 75 mumol DAS was higher by 1.13-, 1.20- and 1.58-fold, respectively, when compared to the control. Purification and quantitation of GST from equal amounts (1.2 g) of control and 50 mumol DAS-treated mice stomach tissues demonstrated that elevation in activity occurred as a result of increased de novo synthesis of the enzyme protein. DAS treatment also resulted in increased pulmonary GST activity, but not in a dose-dependent fashion. On the other hand, treatment of mice with DAS did not alter hepatic GST activity. Interestingly, a small but statistically significant (P less than or equal to 0.05) reduction in kidney GST activity was observed in mice treated with 50 or 75 mumol DAS, as compared to the control. The effect of DAS treatment was also assessed on glutathione (GSH) peroxidase activity, another GSH-dependent detoxification enzyme, in mouse tissues. Treatment of animals with 25, 50 and 75 mumol DAS increased stomach GSH peroxidase activity by 1.64-, 1.93- and 2.52-fold, respectively, over the control. This enzyme activity in the lungs of mice treated with 25, 50 and 75 mumol DAS was higher by 1.44-, 1.54- and 1.21-fold, respectively, when compared to the control. On the other hand, GSH peroxidase activity in liver and kidney was unchanged by DAS treatment. These results suggest that DAS and perhaps other naturally occurring organosulfur compounds may exert an anti-neoplastic effect by modulating GSH-dependent detoxification enzymes.
...
PMID:Effect of diallyl sulfide, a naturally occurring anti-carcinogen, on glutathione-dependent detoxification enzymes of female CD-1 mouse tissues. 188 35

H69AR is a multidrug-resistant small cell lung cancer cell line derived from a drug-sensitive cell line, H69, by selection in doxorubicin. It is cross-resistant to a wide variety of natural product-type antineoplastic agents but does not overexpress P-glycoprotein. In the present study, the levels of GSH and GSH-related enzymes in the H69AR cell line were determined and compared with those found in H69 cells. Unlike other drug-resistant cell lines, GSH levels were diminished 6-fold in H69AR cells (0.67 +/- 0.28 microgram/mg of protein), compared with H69 cells (4.23 +/- 1.17 micrograms/mg of protein) (p less than 0.01). This unusually low level of GSH may explain the pronounced collateral sensitivity of H69AR cells to buthionine sulfoximine (BSO), an inhibitor of the rate-limiting enzyme in GSH biosynthesis (ID50 of 4.4 microM BSO for H69AR cells versus ID50 of 300 microM BSO for H69 cells). BSO did not enhance doxorubicin cytotoxicity in the H69AR cell line, despite further depletion of GSH. GSH-reductase (EC 1.6.4.2) activity was elevated 2-fold in H69AR cells, compared with sensitive H69 cells (75.34 +/- 14.94 versus 38.62 +/- 5.06 nmol of NADPH/min/mg of protein) (p less than 0.05). Both selenium-dependent and -independent GSH-peroxidase (EC 1.11.1.9) activities were unchanged in the resistant H69AR cell line, compared with its parent cell line. gamma-Glutamyl transpeptidase (EC 2.3.2.2) activity was 5-fold elevated in H69AR cells, compared with H69 cells (2.50 +/- 0.44 versus 0.46 +/- 0.21 nmol of p-nitroaniline/min/mg of protein) (p less than 0.01), whereas GSH-S-transferase (EC 2.5.1.18) activity was 10-fold higher (201.98 +/- 43.62 versus 19.77 +/- 1.72 nmol of 1-chloro-2,4-dinitrobenzene/min/mg of protein in H69AR and H69 cells, respectively) (p less than 0.01). The GSH-S-transferases from both cell lines were purified by affinity chromatography and immunoblot analysis identified the GSH-S-transferases as belonging to the anionic pi class. GSH-S-transferases from the mu or alpha classes were not detectable in either cell line. In conclusion, marked differences in GSH levels and the activities of three of four GSH-related enzymes were observed between the multidrug-resistant H69AR cell line and its parent cell line. Further study is required to determine whether these changes are causally related to the development of drug resistance in this model system.
...
PMID:Alterations in glutathione and glutathione-related enzymes in a multidrug-resistant small cell lung cancer cell line. 196 21

Studies have suggested that the alpha class glutathione S-transferase (GST) may protect cells from the chemotherapeutic drugs chlorambucil and melphalan. In order to further define the function of human alpha class GST, a complementary DNA which encodes it was ligated into an expression vector under the direction of the human metallothionein-IIA promoter and stably transfected into human MCF-7 breast cancer cells in conjunction with the G418-selectable plasmid pSV2neo. Clonal cell lines were identified which expressed increased levels of GST enzyme activity (2.2- to 5.6-fold). The transfected cell lines also had increased peroxidase activity using cumene hydroperoxide as the substrate (1.9- to 3.8-fold) which is consistent with the intrinsic peroxidase activity of alpha class GSTs. Southern blot analysis indicated that genomic DNA from these cells contained a fragment indistinguishable from the transfected alpha class GST complementary DNA (850 base pairs); Northern blot analysis of total cellular RNA indicated that these cells contained appropriately sized alpha class GST RNA (980 nucleotides); and Western blot analysis indicated that, while MCF-7 cells contained no detectable alpha class GST protein, the transfected cells contained markedly elevated levels of alpha class GST but no detectable mu or pi class GST. These alpha class GST transfected cells had increased resistance to ethacrynic acid (2.1- to 3.0-fold). However, the transfected cells failed to show any increased resistance measured at the drug dosage which inhibited 50% of the colony formation to the chemotherapeutic drugs chlorambucil, melphalan, Adriamycin, or cisplatin under conditions of either continuous or 1-h drug exposure. Neither was there any change in sensitivity to the cytotoxins benzo(a)pyrene, benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide (anti), or 1-chloro-2,4-dinitrobenzene. These studies indicate that expression of this human alpha class GST by itself in MCF-7 human breast cancer cells does not confer resistance to the chemotherapeutic drugs tested under the conditions used in these studies.
...
PMID:Antineoplastic drug sensitivity of human MCF-7 breast cancer cells stably transfected with a human alpha class glutathione S-transferase gene. 198 77

The effects of GSH depletion in a human breast cancer cell line and a multi-drug resistant subline (ADRr) were determined in a number of experimental conditions. The ADRr cells contained lower GSH concentration which cannot be explained solely on the basis of differences in cell kinetics, and yet the rate-limiting synthetic enzyme gamma-glutamylcysteine synthetase was increased 2-fold. Inhibition of GSH synthesis by BSO resulted in more rapid and more pronounced GSH depletion in ADRr compared to the wild-type cells, suggesting that enhanced GSH utilization and efflux in the resistant cells account for the lowered basal concentration. In addition, the gamma-glutamyl moiety salvage enzyme gamma-glutamyltranspeptidase was reduced markedly in the ADRr cell line. Since these cells have overexpression of the efflux pump protein P-glycoprotein, we examined the effects on cellular GSH of inhibition of the pump's function by verapamil. We found that verapamil significantly depleted cellular GSH. In a rat mammary carcinoma cell line selected in Adriamycin for multi-drug resistance, a similar molecular phenotype has been described including diminished cellular GSH concentration. Verapamil treatment of these cells also resulted in significant depletion of cellular GSH. These results are consistent with the recent report that combined treatment of BSO and verapamil has an additive effect on cytotoxicity. It is likely that decreased basal GSH concentration is due to oxidation and conjugation of it in reactions catalyzed by the enhanced peroxidase and GST found in these cells.
...
PMID:Glutathione depletion in human and in rat multi-drug resistant breast cancer cell lines. 199 9

Glutathione transferase (GST) epsilon (also known as GST2 or GST B1B1), the major Class Alpha GST in human liver has been subjected to oligonucleotide-directed site-specific mutagenesis. Four arginine residues, R13, R20, R69 and R187, of which all but R69 are strictly conserved through GST Classes Alpha, Mu and Pi have been replaced by Ala. The mutant enzymes have been expressed in Escherichia coli, purified by affinity chromatography and characterised. Compared with the wild-type enzyme, all mutant GSTs had altered catalytic properties. All mutants had decreased specific activity with 1-chloro-2,4-dinitrobenzene (CDNB). Mutants R13A, R69A and R187A also showed decreased activities with other substrates such as cumene hydroperoxide (CuOOH) and androstenedione. In contrast, mutant R20A had an increased peroxidase activity and an isomerase activity essentially the same as that of the wild-type GST. With the substrates used, kcat./Km values were decreased for all mutant GSTs. Increases in the [S0.5] values were most significant for glutathione (GSH), while values for CDNB and CuOOH were less markedly affected. Thus, various kinetic data indicate that the GSH affinity has been reduced by the mutations and that this loss of affinity is linked to the decreased specific activities. Inhibition studies showed an increased sensitivity towards S-hexyl-GSH; this was particularly marked for mutant R69A. Mutant R20A had a lowered [I50] value but, in contrast, also the highest [I80] value as compared with the wild-type enzyme. Towards bromosulphophthalein, mutants R20A and R69A had a markedly increased sensitivity, about 35-fold in comparison with the wild-type. The inhibition properties of mutant R187A were similar to those of the wild-type enzyme and the properties of mutant R13A were in between. The increased sensitivity to S-hexyl-GSH, in contrast with the decreased affinity for GSH, was suggested to be due to an altered distribution between conformational states of the enzyme induced by the mutations. The arginine residues in positions 13, 20 and 69 all seem to be important for the catalytic properties of GST. Further, the inhibition studies indicate a role of arginine residues in the stabilisation of conformational states of the enzyme.
...
PMID:Effects of directed mutagenesis on conserved arginine residues in a human Class Alpha glutathione transferase. 200 17

Subcutaneous exposure to vesicants such as butyl 2-chloroethyl sulfide (butyl mustard, BCS) produces local tissue injury (vesication) primarily by alkylation and cross-linking of the purine nucleotides and rapidly binding to proteins. We recently reported that administering BCS can cause other biochemical and morphological alterations, not only in tissues at the injection site but in other areas as well. In this study, we have examined the metabolic effects of BCS administration on the mouse kidney. At 1, 24, and 48 h after injection (5 microliters neat, sc), treated mice were terminated along with an untreated control group, and the kidneys were analyzed for metabolic changes. Glutathione (GSH) peroxidase (GPx) activity markedly increased, (+78 and +85%), but NADP-dependent isocitrate dehydrogenase activity decreased (-43 and -37%) at 1 and 24 h, respectively. Glucose-6-phosphate dehydrogenase (G6PD) remained unchanged at 1 and 24 h, but increased 20% (p less than .05) at 48 h after injection. Kidney glutathione S-transferase (GST) was increased at 24 h after injection. Both total and oxidized GSH levels were significantly lower than control values (approximately 30%) at all time points. Lipid peroxidation, as estimated by the thiobarbituric (TBA) acid-reactive products, was 45% lower (p less than .05) after 1 h. Kidney GPx, G6PD, and GT activities and kidney GSH levels were consistent with changes associated with oxidative stress or detoxication mechanism for BCS. The decrease in TBA-reactive products suggests that mouse kidney metabolic response to BCS injection was different from responses observed for other organs (eyes, brain, and lung).
...
PMID:Metabolic changes in the mouse kidney after subcutaneous injection of butyl 2-chloroethyl sulfide. 203 42


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---