Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P30044 (antioxidant enzyme)
 8,037 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Saccharomyces cerevisiae mutants lacking oxidative stress response genes were used to investigate which genes are required under normal aerobic conditions to maintain cellular redox homeostasis, using intracellular glutathione redox potential (glutathione E(h)) to indicate the redox environment of the cells. Levels of reactive oxygen species (ROS) and mitochondrial membrane potentials (MMP) were also assessed by FACS using dihydroethidium and rhodamine 123 as fluorescent probes. Cells became more oxidised as strains shifted from exponential growth to stationary phase. During both phases the presence of reduced thioredoxin and the activity of glutathione reductase were important for redox homeostasis. Thioredoxin reductase contributed less during exponential phase when there was a strong requirement for active Yap1p transcription factor, but was critical during stationary phase. The absence of ROS detoxification systems, such as catalases or superoxide dismutases, had a lesser effect on glutathione E(h), but a more pronounced effect on ROS levels and MMP. These results reflect the major shift in ROS generation as cells switch from fermentative to respiratory metabolism and also showed that there was not a strong correlation between ROS production, MMP and cellular redox environment. Heterogeneity was detected in populations of strains with compromised anti-oxidant defences, and as cells aged they shifted from one cell type with low ROS content to another with much higher intracellular ROS.
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PMID:Involvement of oxidative stress response genes in redox homeostasis, the level of reactive oxygen species, and ageing in Saccharomyces cerevisiae. 1608 9

Thioredoxin reductase (TrxR) in conjunction with thioredoxin (Trx) is a ubiquitous intracellular oxidoreductase system with antioxidant and redox regulatory roles. In some human tumors, the thioredoxin system is found overexpressed. We have used an antisense approach to investigate whether inhibition of TrxR overexpression can suppress the growth of human hepatocellular carcinoma SMMC-7721 cells. TrxR cDNA fragment was inserted in the antisense direction into pcDNA3.1/myc-His and SMMC-7721 cells were stably transfected with the plasmid construct. The results showed that TrxR antisense RNA could significantly reduce TrxR mRNA level and activity, and suppress the growth of SMMC-7721 cells. Cell-cycle analysis showed G2/M phase arrest in SMMC-7721 cells transfected with TrxR antisense plasmid. TrxR antisense RNA could significantly increase p53 mRNA level and decrease Bcl-2 mRNA level by reverse transcriptase-polymerase chain reaction (RT-PCR). Furthermore a significant decrease in human telomerase reverse transcriptase (hTERT) mRNA level was found in SMMC-7721 cells transfected with TrxR antisense plasmid. Flow cytometry and telomere fluorescence in situ hybridization (Flow FISH) showed that TrxR antisense RNA could significantly reduce the telomere fluorescence in SMMC-7721 cells. The results suggested that TrxR antisene RNA inhibited the growth of SMMC-7721 cells through an accumulation of cell cycle at G2/M phase, an increase in p53 mRNA level and a reduction in telomere fluorescence and Bcl-2, hTERT mRNA levels.
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PMID:Inhibitory effects of thioredoxin reductase antisense RNA on the growth of human hepatocellular carcinoma cells. 1608 46

Thioredoxin reductase (TrxR) is an essential enzyme required for the efficient maintenance of the cellular redox homeostasis, particularly in cancer cells that are sensitive to reactive oxygen species. In mammals, distinct isozymes function in the cytosol and mitochondria. Through an intricate mechanism, these enzymes transfer reducing equivalents from NADPH to bound FAD and subsequently to an active-site disulfide. In mammalian TrxRs, the dithiol then reduces a mobile C-terminal selenocysteine-containing tetrapeptide of the opposing subunit of the dimer. Once activated, the C-terminal redox center reduces a disulfide bond within thioredoxin. In this report, we present the structural data on a mitochondrial TrxR, TrxR2 (also known as TR3 and TxnRd2). Mouse TrxR2, in which the essential selenocysteine residue had been replaced with cysteine, was isolated as a FAD-containing holoenzyme and crystallized (2.6 A; R = 22.2%; R(free) = 27.6%). The addition of NADPH to the TrxR2 crystals resulted in a color change, indicating reduction of the active-site disulfide and formation of a species presumed to be the flavin-thiolate charge transfer complex. Examination of the NADP(H)-bound model (3.0 A; R = 24.1%; R(free) = 31.2%) indicates that an active-site tyrosine residue must rotate from its initial position to stack against the nicotinamide ring of NADPH, which is juxtaposed to the isoalloxazine ring of FAD to facilitate hydride transfer. Detailed analysis of the structural data in conjunction with a model of the unusual C-terminal selenenylsulfide suggests molecular details of the reaction mechanism and highlights evolutionary adaptations among reductases.
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PMID:Crystal structures of oxidized and reduced mitochondrial thioredoxin reductase provide molecular details of the reaction mechanism. 1621 27

Purpose of the study was to investigate the relationship between antioxidant enzyme expression and clinicopathological features in oligodendroglial tumors. The expression of antioxidant enzymes and related proteins (AOEs), manganese superoxide dismutase (MnSOD), thioredoxin (Trx), thioredoxin reductase (TrxR) and gammaglutamylcysteine synthetase catalytic and regulatory subunits (GLCL-C and GLCL-R), was studied in 85 oligodendroglial tumors. The material included 71 primary (43 grade II and 28 grade III) and 14 recurrent (6 grade II and 8 grade III) tumors. Fifty-seven cases were pure oligodendrogliomas and 28 were mixed oligoastrocytomas. Immunoreactivity for MnSOD was found in 89%, Trx in 29%, TrxR in 76%, GLCL-C in 70% and GLCL-R in 68% of cases. Increased Trx expression was associated with higher tumor grade, cell proliferation and apoptosis (P=0.006, P=0.001 and P=0.003, Mann-Whitney test). Pure oligodendrogliomas showed more intense staining than oligoastrocytomas, especially for MnSOD (P=0.002, Mann-Whitney test). In the total series Trx was associated with poor prognosis in univariate survival analysis (P=0.0343, log-rank test) and furthermore in Cox multivariate analysis (P=0.009) along with age (P=0.002). The results suggest that the expression of Trx has a correlation to patient outcome and that there may be some association between AOEs, like MnSOD and Trx, and clinicopathological features of oligodendrogliomas.
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PMID:Antioxidant enzymes in oligodendroglial brain tumors: association with proliferation, apoptotic activity and survival. 1629 83

Oxidative stress is thought to contribute to the initiation and progression of atherosclerosis. As glutathione peroxidase-1 (Gpx1) is an antioxidant enzyme that detoxifies lipid hydroperoxides, we tested the impact of Gpx1 deficiency on atherosclerotic processes and antioxidant enzyme expression in mice fed a high-fat diet (HFD). After 12 weeks of HFD, atherosclerotic lesions at the aortic sinus were of similar size in control and Gpx1-deficient mice. However, after 20 weeks of HFD, lesion size increased further in control but not in Gpx1-deficient mice, even though plasma and aortic wall markers of oxidative damage did not differ between groups. In control mice, the expression of Gpx1 increased and that of Gpx3 decreased at the aortic sinus after 20 weeks of HFD, with no change in the expression of Gpx2, Gpx4, catalase, peroxiredoxin-6, glutaredoxin-1 and -2, or thioredoxin-1 and -2. By comparison, in Gpx1-deficient mice, the expression of antioxidant genes was unaltered except for a decrease in glutaredoxin-1 and an increase in glutaredoxin-2. These changes were associated with increased expression of the proinflammatory marker monocyte chemoattractant protein-1 in control mice but not in Gpx1-deficient mice. In summary, a specific deficiency in Gpx1 was not accompanied by an increase in markers of oxidative damage or increased atherosclerosis in a murine model of HFD-induced atherogenesis.
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PMID:Lack of the antioxidant glutathione peroxidase-1 does not increase atherosclerosis in C57BL/J6 mice fed a high-fat diet. 1650 38

Thioredoxin reductase and thioredoxin constitute the cellular thioredoxin system, which provides reducing equivalents to numerous intracellular target disulfides. Mammalian thioredoxin reductase contains the rare amino acid selenocysteine. Known as the "21st" amino acid, selenocysteine is inserted into proteins by recoding UGA stop codons. Some model eukaryotic organisms lack the ability to insert selenocysteine, and prokaryotes have a recoding apparatus different from that of eukaryotes, thus making heterologous expression of mammalian selenoproteins difficult. Here, we present a semisynthetic method for preparing mammalian thioredoxin reductase. This method produces the first 487 amino acids of mouse thioredoxin reductase-3 as an intein fusion protein in Escherichia coli cells. The missing C-terminal tripeptide containing selenocysteine is then ligated to the thioester-tagged protein by expressed protein ligation. The semisynthetic version of thioredoxin reductase that we produce in this manner has k(cat) values ranging from 1500 to 2220 min(-)(1) toward thioredoxin and has strong peroxidase activity, indicating a functional form of the enzyme. We produced the semisynthetic thioredoxin reductase with a total yield of 24 mg from 6 L of E. coli culture (4 mg/L). This method allows production of a fully functional, semisynthetic selenoenzyme that is amenable to structure-function studies. A second semisynthetic system is also reported that makes use of peptide complementation to produce a partially active enzyme. The results of our peptide complementation studies reveal that a tetrapeptide that cannot ligate to the enzyme (Ac-Gly-Cys-Sec-Gly) can form a noncovalent complex with the truncated enzyme to form a weak complex. This noncovalent peptide-enzyme complex has 350-500-fold lower activity than the semisynthetic enzyme produced by peptide ligation.
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PMID:Semisynthesis and characterization of mammalian thioredoxin reductase. 1661 5

Thioredoxin reductase (TR) and thioredoxin (Trx) define a major cellular redox system that maintains cysteine residues in numerous proteins in the reduced state. Both cytosolic (TR1 and Trx1) and mitochondrial (TR3 and Trx2) enzymes are essential in mammals, but the function of the mitochondrial system is less understood. In this study, we characterized subcellular localization of three TR3 forms that are generated by alternative first exon splicing and that differ in their N-terminal sequences. Only one of these forms resides in mitochondria, whereas the two other isoforms are cytosolic. Consistent with this finding, TR3 did not have catalytic preferences for mitochondrial Trx2 versus cytosolic Trx1, both of which could serve as TR3 substrates. Similarly, TR1 was equally active with Trx1, Trx2, or a bacterial Trx. We generated recombinant selenoprotein forms of TR1 and TR3 and found that these enzymes were inhibited by zinc, but not by calcium or cobalt ions. We further developed a proteomic method for identification of targets of TRs in mammalian cells utilizing affinity columns containing recombinant TR3 forms differing in C-terminal sequences. Using this procedure, we found that Trx1 was the major target of TR3 in both rat and mouse liver cytosol. The truncated form of TR3 lacking selenocysteine was particularly efficient in binding Trx1, consistent with the previously observed role of truncated TR1 in apoptosis. Overall, these data establish that the function of TR3 is not limited to its role in Trx2 reduction.
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PMID:Characterization of alternative cytosolic forms and cellular targets of mouse mitochondrial thioredoxin reductase. 1677 13

Thioredoxin reductase catalyzes the NADPH-dependent reduction of the catalytic disulfide bond of thioredoxin. In mammals and other higher eukaryotes, thioredoxin reductases contain the rare amino acid selenocysteine at the active site. The mitochondrial enzyme from Caenorhabditis elegans, however, contains a cysteine residue in place of selenocysteine. The mitochondrial C. elegans thioredoxin reductase was cloned from an expressed sequence tag and then produced in Escherichia coli as an intein-fusion protein. The purified recombinant enzyme has a kcat of 610 min(-1) and a Km of 610 microM using E. coli thioredoxin as substrate. The reported kcat is 25% of the kcat of the mammalian enzyme and is 43-fold higher than a cysteine mutant of mammalian thioredoxin reductase. The enzyme would reduce selenocysteine, but not hydrogen peroxide or insulin. The flanking glycine residues of the GCCG motif were mutated to serine. The mutants improved substrate binding, but decreased the catalytic rate.
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PMID:Characterization of mitochondrial thioredoxin reductase from C. elegans. 1678 Jul 99

Thioredoxin reductase (TrxR), a component of the redox control system involving thioredoxin (Trx), is implicated in defense against oxidative stress, control of cell growth and proliferation, and regulation of apoptosis. In the present study a stable transfectant was made by introducing the vector pcDNA3.0 harboring the fission yeast TrxR gene into COS-7 African green monkey kidney fibroblast cells. The exogenous TrxR gene led to an increase in TrxR activity of up to 3.2-fold but did not affect glutathione (GSH) content, or glutaredoxin and caspase-3 activities. Levels of reactive oxygen species (ROS), but not those of nitric oxide (NO), were reduced. Conversely, 1-chloro-2,4-dinitrobezene (CDNB), an irreversible inhibitor of mammalian TrxR, enhanced ROS levels in the COS-7 cells. After treatment with hydrogen peroxide, the level of intracellular ROS was lower in the transfectants than in the vector control cells. These results confirm that TrxR is a crucial determinant of the level of cellular ROS during oxidative stress as well as in the normal state.
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PMID:Effects of heterologous expression of thioredoxin reductase on the level of reactive oxygen species in COS-7 cells. 1695 58

Cyclophosphamide (CTX) is in the nitrogen mustard group of alkylating antineoplastic chemotherapeutic agents. It is one of the most frequently used antitumor agents for the treatment of a broad spectrum of human cancers. Thioredoxin reductase (TrxR) catalyze the NADPH-dependent reduction of thioredoxin and play an important role in multiple cellular events related to carcinogenesis including cell proliferation, apoptosis, and cell signaling. This enzyme represents a promising target for the development of cytostatic agents. The purpose of this study is to determine whether CTX could target TrxR in vivo. Lewis lung carcinoma and solid H22 hepatoma treated with 50-250 mg/kg CTX for 3 h lost TrxR activity in a dose-dependent fashion. Over 75% and 95% of TrxR activity was lost at the dose of 250 mg/kg. There was, however, a recovery of TrxR activity such that it attained normal levels by 120 h after a dose of 250 mg/kg. In addition, we found that CTX caused a preferential TrxR inhibition over other antioxidant enzymes, such as glutathione peroxidase, catalase, and superoxide dismutase. We also used ascites H22 cells to investigate cancer cells response after TrxR was inhibited by CTX in vivo since CTX is needed to be activated by liver cytochrome P450 enzymes. The time course and dose-dependent changes of cellular TrxR activity were similar with those in tumor tissue. CTX caused a dose-dependent cellular proliferation inhibition which was positively correlated with TrxR inhibition at 3 h. Furthermore, when 3 h CTX-treated cells with various TrxR backgrounds, harvested from ascites-bearing mice, were implanted into mice, the proliferations of these cells were again proportionally dependent on TrxR activity. The TrxR inhibition could thereby be considered as a crucial mechanism contributing to anticancer effect seen upon clinical use of CTX.
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PMID:Cyclophosphamide as a potent inhibitor of tumor thioredoxin reductase in vivo. 1715 7


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