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 potential role of transforming growth factor-beta in in vivo resistance was examined by administration of transforming growth factor-beta-neutralizing antibodies to animals bearing the EMT-6/Parent tumor or the antitumor alkylating resistance tumors, EMT-6/CTX or EMT-6/CDDP. Treatment of tumor bearing animals with anti-TGF-beta antibodies by intraperitoneal injection daily on days 0-8 post-tumor cell implantation increased the sensitivity of the EMT-6/Parent tumor to cyclophosphamide (CTX) and cisplatin (CDDP) and markedly increased the sensitivity of the EMT-6/CTX tumor to CTX and the EMT6/CDDP tumor to CDDP, as determined by tumor cell survival assay. Bone marrow granulocyte-macrophage colony-forming units (CFU-GM) survival was determined from these same animals. The increase in the sensitivity in the tumors upon treatment with the anti-TGF-beta antibodies was also observed in increased sensitivity of the bone marrow CFU-GM to CTX and CDDP. Treatment of non-tumor-bearing animals with the anti-TGF-beta regimen did not alter blood ATP or serum glucose level but did decrease serum lactate levels. This treatment also decreased hepatic glutathione, glutathione S-transferase, glutathione reductase, and glutathione peroxidase in non-tumor bearing animals by 40-60% but increased hepatic cytochrome P450 reductase in these normal animals. Animals bearing the EMT-6/CTX and EMT-6/CDDP tumors had higher serum lactate levels than normal or EMT-6/Parent tumor-bearing animals; these were decreased by the anti-TGF-beta regimen. Treatment of animals bearing any of the three tumors with the anti-TGF-beta regimen decreased by 30-50% the activity of hepatic glutathione S-transferase and glutathione peroxidase, and increased by 35-80% the activity of hepatic cytochrome P450 reductase. In conclusion, treatment with transforming growth factor-beta-neutralizing antibodies restored drug sensitivity in the alkylating agent-resistant tumors, altering both the tumor and host metabolic states.
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PMID:Transforming growth factor-beta in in vivo resistance. 861 16

A network composed of activation and inactivation pathways to regulate mitomycin C (MMC) action is suggested to exist in human cancer cells. COLO201 colon cancer cells were stably transfected with human NQO1 cDNA that encodes NAD(P)H:quinone oxidoreductase (DT-diaphorase, DTD), and a clonal cell line with about 57-fold elevated DTD activity was obtained. Northern analysis revealed that expression of the NADPH:cytochrome P450 reductase (P450 reductase) gene was decreased in the transfectant, COLO201/NQO1, associated with the increase of NQO1 expression. Biochemical characterization of the cells showed a significant increase of the glutathione (GSH) content concomitantly with the decrease of the P450 reductase activity. As a result of these coordinated modulations, sensitivity of COLO201/NQO1 to MMC was not increased as compared to the parent cells. Analyses of inhibition by specific inhibitors of DTD, P450 reductase and glutathione S-transferase (GST) in 5 human colon cancer cell lines including the transfectant showed that DTD and P450 reductase play significant roles in MMC activation in cells with sufficiently high DTD activity and with marginal DTD activity, respectively. In contrast, GST appeared to participate in MMC inactivation in cells with a high level of GST activity. These results indicated that DTD, P450 reductase, GSH and GST may act together compensatively or competitively, depending on their levels in cells, to determine the cellular sensitivity to MMC.
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PMID:Regulatory network of mitomycin C action in human colon cancer cells. 1039 Oct 98

Protein-calorie malnutrition (PCM) can develop both from inadequate food intake and as a consequence of diseases such as cancer and AIDS. Several studies have shown that PCM can alter drug clearance but little information is available on the effect of PCM on individual cytochrome P450 isoforms and phase II conjugation enzymes. The aim of the present study was to begin a systematic evaluation of the effect of PCM on the activity of individual drug metabolizing enzymes in a rat model of PCM. Control and PCM rats received isocaloric diets which contained either 21% or 5% (deficient) protein. After 3 weeks, the animals were sacrificed and microsomal and cytosolic fractions prepared. Ethoxyresorufin O-deethylation (EROD), chlorzoxazone 6-hydroxylation, dextromethorphan N- and O-demethylation and 1-chloro-2,4-dinitrobenzene (CDNB) conjugation were used as measures of CYP1A, CYP2E1, CYP3A2, CYP2D1 and glutathione S-transferase (GST) activity, respectively. Additionally, NADPH-cytochrome P450 reductase activity was measured in the liver microsomes. PCM significantly reduced the maximum velocity (Vmax) of all model reactions studied. However, differential effects were observed with respect to K(m) values of the reactions. The K(m) values for EROD and dextromethorphan N-demethylation were significantly increased in PCM animals, whereas the K(m) values for chlorzoxazone 6-hydroxylation and dextromethorphan O-demethylation were decreased. In contrast, the K(m) value for CDNB conjugation was unchanged. When NADPH-cytochrome P450 reductase activity was compared, a 29% reduction in reductase activity was noted in PCM animals as compared to controls. Thus, it appears that PCM decreases the overall activity of certain phase I and phase II metabolism enzymes in rat liver while exhibiting differential effects on K(m). Furthermore, this reduction in activity may be due in part to diminished activity of cytochrome P450 reductase.
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PMID:Effect of protein-calorie malnutrition on cytochromes P450 and glutathione S-transferase. 1051 Jul 41

Evidence for redox-dependent toxicities of mitomycin C (MMC) and diepoxybutane (DEB), through different mechanisms, has been related to the phenotypic defect(s) of Fanconi's anaemia (FA) cells, due to their excess sensitivity to these agents. Recent data have pointed to interactions of the FANCC protein (encoded by the FA complementation group C gene, FA-C) with NADPH cytochrome P450 reductase and glutathione S-transferase (GST), two activities involved in either triggering or detoxifying reactive intermediates, including xenobiotics and reactive oxygen species. A body of evidence points to: (i) oxygen hypersensitivity of FA cells; (ii) oxygen-dependent MMC and DEB toxicity; (iii) excess oxidative DNA damage in FA cells; and (iv) DEB-induced glutathione depletion and GST inhibition. The available evidence corroborates the previously suggested role for oxidative stress in FA phenotype and disease progression, shedding new light on the redox-dependent mechanisms in MMC and DEB toxicities, and suggesting a direct association of oxidative stress with the primary genetic defect in FA.
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PMID:Mitomycin C and diepoxybutane action mechanisms and FANCC protein functions: further insights into the role for oxidative stress in Fanconi's anaemia phenotype. 1078 35

We examined three primary variables in the preparation of human liver microsomes. In three experiments, each using three livers, we manipulated 1) the force of the first centrifugation (9,000, 10,500, or 12,000g); 2) the presence of sucrose in the homogenization buffer; and 3) the number of homogenizing strokes (6, 8, or 10). Sedimentation plots for the marker enzymes succinate dehydrogenase, NADPH cytochrome P450 reductase (reductase), and glutathione S-transferase in the resulting premicrosomal, microsomal, and cytosolic fractions suggest that enhanced purity of microsomes can be obtained by reducing force of centrifugation, including sucrose, and increasing the number of homogenization strokes. Each microsomal fraction was also assayed for protein content, cytochrome P450, NADH cytochrome b(5) reductase, cytochrome b(5), absorbance at 420, p-nitrophenol hydroxylation, tolbutamide hydroxylation, dextromethorphan N- and O-demethylation, glucuronidation of morphine and 1-naphthol, and ester cleavage of p-nitrophenolacetate. These microsomal indicators were ranked and tested for statistical differences. The use of 9000g statistically increased optimal recovery (per gram of liver) and specific activity (per milligram of protein). The inclusion of sucrose improved activity specific to reductase activity. Ten homogenization strokes improved activity specific to reductase activity. Substrate-dependent activities of dextromethorphan O-demethylation to dextrorphan and the N-demethylation of l-alpha-acetylmethadol (LAAM) to norLAAM and dinorLAAM were compared in microsomes prepared with or without sucrose and microsomes prepared using 9,000 or 12,000g force, respectively. No significant differences were found in the concentration-dependent activities. Variation of the methods used to prepare human liver microsomes can significantly affect the recovery and specific activity of microsomal components; however, they do not appear to affect enzyme kinetics.
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PMID:Variables in human liver microsome preparation: impact on the kinetics of l-alpha-acetylmethadol (LAAM) n-demethylation and dextromethorphan O-demethylation. 1118 2

The effects of two doses (50 and 100 mg/kg body wt/day for 14 days) of an 80% hydroalcohol extract of Andrographis paniculata and butylated hydroxyanisole (BHA) were examined on drug metabolizing enzymes, antioxidant enzymes, glutathione content, lactate dehydrogenase (LDH) and lipid peroxidation in the liver of Swiss albino mice (6-8 weeks old). The effect of the extract and BHA were also examined on lung, kidney and forestomach for the activities of glutathione S-transferase (GST), DT-diaphorase (DTD), superoxide dismutase (SOD) and catalase. A significant increase in the levels of acid soluble sulphydryl (-SH) content, cytochrome P450, cytochrome P450 reductase, cytochrome b5 reductase, GST, DTD and SOD were observed at both dose levels of extract treatment while catalase, glutathione peroxidase and glutathione reductase (GR) showed significant increases only at the higher dose in the liver. Both Andrographis treated groups showed a significant decrease in activity of LDH and malondialdehyde (MDA) formation. BHA treated mice showed a significant increase in the levels of cytochrome b(5), GST, DTD, -SH content, GR and catalase in liver; while LDH and MDA levels were reduced significantly compared with their control values. In the lung, SOD, catalase and DTD, in the kidney catalase, DTD and GST, and in the forestomach SOD and DTD showed a significant increase at both dose levels of treatment. In BHA treated mice GST, DTD and catalase were significantly induced in the lung and along with these enzymes SOD was also induced in the kidney. In the case of the forestomach of BHA treated mice GST, DTD and SOD were enhanced significantly. These findings indicate the chemopreventive potential of Andrographis paniculata against chemotoxicity including carcinogenicity.
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PMID:Modulatory influence of Andrographis paniculata on mouse hepatic and extrahepatic carcinogen metabolizing enzymes and antioxidant status. 1150 28

Human methionine synthase reductase (MSR) catalyzes the NADPH-dependent reductive methylation of methionine synthase. MSR is 78 kDa flavoprotein belonging to a family of diflavin reductases, with cytochrome P450 reductase (CPR) as the prototype. MSR and its individual flavin-binding domains were cloned as GST-tagged fusion proteins for expression and purification from Escherichia coli. The isolated flavin domains of MSR retain UV-visible and secondary structural properties indicative of correctly folded flavoproteins. Anaerobic redox titrations on the individual domains assisted in assignment of the midpoint potentials for the high- and low-potential flavin. For the isolated FMN domain, the midpoint potentials for the oxidized/semiquinone (ox/sq) couple and semiquinone/hydroquinone (sq/hq) couple are -112 and -221 mV, respectively, at pH 7.0 and 25 degrees C. The corresponding couples in the isolated FAD domain are -222 mV (ox/sq) and -288 mV (sq/hq). Both flavins form blue neutral semiquinone species characterized by broad absorption peaks in the long-wavelength region during anaerobic titration with sodium dithionite. In full-length MSR, the values of the FMN couples are -109 mV (ox/sq) and -227 mV (sq/hq), and the corresponding couple values for FAD are -254 mV (ox/sq) and -291 mV (sq/hq). Separation of the MSR flavins does not perturb their thermodynamic properties, as midpoint potentials for all four couples are similar in isolated domains and in full-length MSR. The redox properties of MSR are discussed in relation to other members of the diflavin oxidoreductase family and the mechanism of electron transfer.
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PMID:Molecular dissection of human methionine synthase reductase: determination of the flavin redox potentials in full-length enzyme and isolated flavin-binding domains. 1266 82

o-Quinones are easily formed by oxidation of physiologically relevant catechols. These reactions mainly occur in two specialized cells, catecholaminergic neurons and melanocytes. Both types of cells are related ontogenetically, as they arise from the neural crest during the developmental differentiation. o-Quinones are used to form melanin, a protective pigment formed by different mechanisms in melanocytes and catecholaminergic neurons. However, the reactivity of these quinones makes their presence in the cytosol dangerous for the cell survival and these compounds have been proposed as degenerative and apoptotic agents. Thus, melanin-producing cells show several potential mechanisms to protect themselves against the noxious effects of o-quinones. In melanocytes, the most effective autoprotecting mechanisms are the existence of malanosomes as a confined site for melano-synthesis and the action of tyrosinase-related protein 2 (TRP2) to drive L-dopachrome to 5,6-dihydroxyindole-2-carboxylic acid minimizing the formation of 5,6-dihydroxyindole. In catecholaminergic neurons, recent data suggest that glutathione transferase (GST M2-2 isoenzyme) and macrophage migration inhibitory factor (MIF) are very effective in preventing long-lived formation of dopaminechrome and noradrenochrome, although the detoxification reactions are different (conjugation to GSH or isomerization respectively). These mechanisms are less efficient for adrenochrome, although MIF and GST M1-1 could also catalyze similar reactions using this compound as substrate. In addition, the formation of adrenochrome is still under discussion, and adrenolutin formation could contribute to deactivate its harmful effects. The contribution of D-dopachrome tautomerase to these mechanisms is yet unknown, although in contrast to MIF, that enzyme does not recognize catecholaminechromes as substrates. Diaphorase could also be protective against quinones, since this enzyme catalyzes their bielectronic reduction back to catechols, thus preventing the formation of chrome species. This activity has been described in melanocytes and neurons, so that its contribution should be further investigated. In contrast to diaphorase, cytochrome P450 reductase should not be considered a protective enzyme, since its monoelectronic reduction of quinones leads to formation of semiquinones, that is, even more noxious than the quinones.
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PMID:Neurotoxicity due to o-quinones: neuromelanin formation and possible mechanisms for o-quinone detoxification. 1283 99

The rationale fo the development of prodrugs relies upon delivery of higher concentrations of a drug to target cells compared to administration of the drug itself. In the last decades, numerous prodrugs that are enzymatically activated into anti-cancer agents have been developed. This review describes the most important enzymes involved in prodrug activation notably with respect to tissue distribution, up-regulation in tumor cells and turnover rates. The following endogenous enzymes are discussed: aldehyde oxidase, amino acid oxidase, cytochrome P450 reductase, DT-diaphorase, cytochrome P450, tyrosinase, thymidylate synthase, thymidine phosphorylase, glutathione S-transferase, deoxycytidine kinase, carboxylesterase, alkaline phosphatase, beta-glucuronidase and cysteine conjugate beta-lyase. In relation to each of these enzymes, several prodrugs are discussed regarding organ- or tumor-selective activation of clinically relevant prodrugs of 5-fluorouracil, axazaphosphorines (cyclophosphamide, ifosfamide, and trofosfamide), paclitaxel, etoposide, anthracyclines (doxorubicin, daunorubicin, epirubicin), mercaptopurine, thioguanine, cisplatin, melphalan, and other important prodrugs such as menadione, mitomycin C, tirapazamine, 5-(aziridin-1-yl)-2,4-dinitrobenzamide, ganciclovir, irinotecan, dacarbazine, and amifostine. In addition to endogenous enzymes, a number of nonendogenous enzymes, used in antibody-, gene-, and virus-directed enzyme prodrug therapies, are described. It is concluded that the development of prodrugs has been relatively successful; however, all prodrugs lack a complete selectivity. Therefore, more work is needed to explore the differences between tumor and nontumor cells and to develop optimal substrates in terms of substrate affinity and enzyme turnover rates fo prodrug-activating enzymes resulting in more rapid and selective cleavage of the prodrug inside the tumor cells.
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PMID:Enzyme-catalyzed activation of anticancer prodrugs. 1500 63

Resveratrol, a polyphenolic compound found in grape skin and peanuts has been shown to prevent many diseases including cardiovascular diseases and cancer. To better understand resveratrol's potential in vivo toxicity, we studied the dose response using cDNA stress arrays coupled with drug metabolizing enzymatic (DME) assays to investigate the expression of stress-responsive genes and Phase I and II detoxifying enzymes in rat livers. Male and female CD rats were treated with high doses of resveratrol (0.3, 1.0 and 3.0 gm/kg/day) for a period of 28 days. Total RNA from rat liver was reverse-transcribed using gene-specific primers and hybridized to stress-related cDNA arrays. Among female rats, Phase I DME genes were repressed at 0.3 and 1.0 gm/kg/day doses, while genes such as manganese superoxide dismutase, cytochrome P450 reductase, quinone oxidoreductase and thiosulfate sulfurtransferase demonstrated a dose-dependent increase in gene expression. The modulation of these liver genes may implicate the potential toxicity as observed among the rats at the highest dose level of resveratrol. Real-Time PCR was conducted on some of the Phase II DME genes and anti-oxidant genes to validate the cDNA array data. The gene expression from real-time PCR demonstrated good correlation with the cDNA array data. UGT1A genes were amongst the most robustly induced especially at the high doses of resveratrol. We next performed Phase I and Phase II enzymatic assays on cytochrome P450 2E1 (CYP2E1), cytochrome P450 1A1 (CYP1A1), NAD(P)H:quinone oxidoreductase (NQO1), glutathione S-transferase (GST) and UDP-glucuronosyl transferase (UGT). Induction of Phase II detoxifying enzymes was most pronounced at the highest dose of resveratrol. CYP1A1 activity demonstrated a decreasing trend among the 3 dose groups and CYP2E1 activity increased marginally among female rats over controls. In summary, at lower doses of resveratrol there are few significant changes in gene expression whereas the modulation of liver genes at the high dose of resveratrol may implicate the potential toxicity observed.
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PMID:Toxicogenomics of resveratrol in rat liver. 1574 24


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