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:1.6.5.2 (NQO1)
6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have constructed a tobacco psbA gene deletion mutant that is devoid of photosystem II (PSII) complex. Analysis of thylakoid membranes revealed comparable amounts, on a chlorophyll basis, of photosystem I (PSI), the cytochrome b6f complex and the PSII light-harvesting complex (LHCII) antenna proteins in wild-type (WT) and DeltapsbA leaves. Lack of PSII in the mutant, however, resulted in over 10-fold higher relative amounts of the thylakoid-associated plastid terminal oxidase (PTOX) and the NAD(P)H dehydrogenase (NDH) complex. Increased amounts of Ndh polypeptides were accompanied with a more than fourfold enhancement of NDH activity in the mutant thylakoids, as revealed by in-gel NADH dehydrogenase measurements. NADH also had a specific stimulating effect on P700+ re-reduction in the DeltapsbA thylakoids. Altogether, our results suggest that enhancement of electron flow via the NDH complex and possibly other alternative electron transport routes partly compensates for the loss of PSII function in the DeltapsbA mutant. As mRNA levels were comparable in WT and DeltapsbA plants, upregulation of the alternative electron transport pathways (NDH complex and PTOX) occurs apparently by translational or post-translational mechanisms.
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PMID:Deletion of the tobacco plastid psbA gene triggers an upregulation of the thylakoid-associated NAD(P)H dehydrogenase complex and the plastid terminal oxidase (PTOX). 1296 24

Dworkin, Martin (University of Minnesota, Minneapolis), and Donald J. Niederpruem. Electron transport system in vegetative cells and microcysts of Myxococcus xanthus. J. Bacteriol. 87:316-322. 1964.-Respiration by intact cells of the fruiting myxobacterium Myxococcus xanthus is cyanide-sensitive and can be demonstrated in the vegetative cells but not in the microcysts. Cell-free particles from both vegetative cells and microcysts have cyanide-sensitive reduced nicotinamide adenine dinucleotide (NADH) oxidase, diaphorase, NADH cytochrome c reductase, and cytochrome oxidase activities. While the vegetative cell specific activities for NADH oxidase and diaphorase are slightly higher than those for the microcysts, the microcysts have ten times the cytochrome c reductase and cytochrome oxidase activities of the vegetative cells. Furthermore, the respiration of the microcyst particles is considerably less cyanide-sensitive than is that of the vegetative-cell particles. Difference spectra of the cell-free particles of vegetative cells and microcysts are qualitatively identical, showing the presence of b- and c-type cytochrome and flavoprotein. The a-type pigments are clearly present in the extracts of the vegetative cells and are suggested by the spectrum of the microcyst particles. The cytochrome oxidase activity of both extracts is consistent with the presence of a-type pigments in both. The spectra of the carbon monoxide-binding pigments were determined and, by this parameter, qualitative differences appear between the vegetative cells and the microcysts.
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PMID:ELECTRON TRANSPORT SYSTEM IN VEGETATIVE CELLS AND MICROCYSTS OF MYXOCOCCUS XANTHUS. 1415 Oct 50

Downey, Ronald J. (University of Notre Dame, Notre Dame, Ind.). Vitamin K-mediated electron transfer in Bacillus subtilis. J. Bacteriol. 88:904-911. 1964.-Electron transfer enzymes were obtained from log-phase cells of Bacillus subtilis after aerobic and anaerobic cultivation. The cytochrome content was found to be related to oxygen tension, there being little, if any, cytochrome operative in anaerobic cells. Vitamin K levels in the two cell types did not vary as markedly. A soluble diaphorase-type flavoprotein was obtained from both types of cells which reacted with vitamin K(2), K(3), and certain dyes but not bovine cytochrome c. Almost 90% of this diaphorase activity was leached from intact protoplasts without the use of solvating agents or sonic oscillation. Electron transport particles capable of coupled phosphorylation were inhibited by light (360 mmu) or 2,3-dimercaptopropanol (BAL), whereas these had no effect on the diaphorase activity. Phosphorylation in a BAL-inhibited system was restored after addition of the soluble diaphorase from either aerobic or anaerobic cells. The results suggested that soluble flavoprotein components are linked to vitamin K in both fermentative and phosphorylative pathways, and that this segment is indispensable to aerobic and anaerobic respiration in the bacillus.
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PMID:VITAMIN K-MEDIATED ELECTRON TRANSFER IN BACILLUS SUBTILIS. 1421 53

The composition and dynamics of membrane protein complexes were studied in the cyanobacterium Synechocystis sp. PCC 6803 by two-dimensional blue native/SDS-PAGE followed by matrix-assisted laser-desorption ionization time of flight mass spectrometry. Approximately 20 distinct membrane protein complexes could be resolved from photoautotrophically grown wild-type cells. Besides the protein complexes involved in linear photosynthetic electron flow and ATP synthesis (photosystem [PS] I, PSII, cytochrome b6f, and ATP synthase), four distinct complexes containing type I NAD(P)H dehydrogenase (NDH-1) subunits were identified, as well as several novel, still uncharacterized protein complexes. The dynamics of the protein complexes was studied by culturing the wild type and several mutant strains under various growth modes (photoautotrophic, mixotrophic, or photoheterotrophic) or in the presence of different concentrations of CO2, iron, or salt. The most distinct modulation observed in PSs occurred in iron-depleted conditions, which induced an accumulation of CP43' protein associated with PSI trimers. The NDH-1 complexes, on the other hand, responded readily to changes in the CO2 concentration and the growth mode of the cells and represented an extremely dynamic group of membrane protein complexes. Our results give the first direct evidence, to our knowledge, that the NdhF3, NdhD3, and CupA proteins assemble together to form a small low CO2-induced protein complex and further demonstrate the presence of a fourth subunit, Sll1735, in this complex. The two bigger NDH-1 complexes contained a different set of NDH-1 polypeptides and are likely to function in respiratory and cyclic electron transfer. Pulse labeling experiments demonstrated the requirement of PSII activity for de novo synthesis of the NDH-1 complexes.
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PMID:Towards functional proteomics of membrane protein complexes in Synechocystis sp. PCC 6803. 1473 74

The cytochrome b6f complex from the thermophilic cyanobacterium Mastigocladus laminosus and spinach chloroplasts has been purified as a dimeric species. It was found by electrospray ionization mass spectroscopy to contain eight and nine subunits, respectively, and dimeric masses of 217,070 and 286,454 Da. The subunits common to the complex from both sources are petA (cytochrome f), B (cytochrome b6), C (Rieske iron-sulfur protein), D (subunit IV), and small 3.2-4.2 kDa polypeptides petG,L,M, and N. The ninth polypeptide, the 35 kDa petH poly-peptide in the spinach complex, was identified as ferredoxin NADP reductase (FNR), which binds to the complex tightly at a stoichiometry of approx 0.9 (cyt f)-1. The spinach complex contains diaphorase activity diagnostic of FNR, and is active in facilitating ferredoxin-dependent electron transfer from NADPH to the cytochrome b6f complex. The purified cytochrome b6f complex contains stoichiometrically bound chlorophyll a and beta-carotene at a ratio of one per cytochrome f, and bound lipid, in which MGDG and PG are the most abundant species. The delipidated highly purified complexes are active immediately after preparation and for approx 1 wk if left on ice, transferring 300-350 electrons/cyt f/s. Both complexes are subject to proteolysis and associated loss of activity if left for extended periods (>1 wk) at room temperature. Addition of pure synthetic lipid to the delipidated M. laminosus complex (the "lipid augmentation" technique) allows rapid and ready formation of large (>0.2 mm) crystals suitable for x-ray diffraction analysis and structure determination, which diffract with good statistics to 3.0 A.
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PMID:Purification and crystallization of the cytochrome b6f complex in oxygenic photosynthesis. 1518 70

The effect of two different doses (400 and 800 mg/kg body wt/day for 15 days) of a 95% ethanolic extract of the seeds of Brassica compestris (var sarason) was examined on carcinogen metabolizing phase-I and phase-II enzymes,antioxidant enzymes and glutathione content and lipid peroxidation in the liver of Swiss albino mice. Positive control mice were treated with butylated hydroxyanisole (BHA). Significant elevation in the levels of cytochrome p450 (p<0,.05), cytochrome b5 (p < 0.05) glutathione s-transferase (p<0.01), DT-diaphorase (p<0.05), superoxide dismutase (p<0.01), catalase (p < 0.001) and reduced glutathione (p<0.001) was noted in the group treated with 800 mg/kg body wt. of Brassica extract in comparison with the negative control group. Brassica compestris acted as a bifunctional inducer since it induced both phase - I and phase - H enzyme systems. Since phase-I and phase-II enzymes are considered to be reliable markers for evaluating the chemoprevention efficacy of particular test materials,these findings are suggestive of potential chemopreventive roles for Brassica seed extract.
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PMID:Chemomodulatory action of Brassica compestris (var sarason) on hepatic carcinogen metabolizing enzymes, antioxidant profiles and lipid peroxidation. 1524 24

Although photosystem I (PSI) cyclic electron transport is essential for plants, our knowledge of the route taken by electrons is very limited. To assess whether ferredoxin (Fd) donates electrons directly to plastoquinone (PQ) or via a Q-cycle in the cytochrome (cyt) b(6)f complex in PSI cyclic electron transport, we characterized the activity of PSI cyclic electron transport in an Arabidopsis mutant, pgr1 (proton gradient regulation). In pgr1, Q-cycle activity was hypersensitive to acidification of the thylakoid lumen because of an amino acid alteration in the Rieske subunit of the cyt b(6)f complex, resulting in a conditional defect in Q-cycle activity. In vitro assays using ruptured chloroplasts did not show any difference in the activity of PGR5-dependent PQ reduction by Fd, which functions in PSI cyclic electron transport in vivo. In contrast to the pgr5 defect, the pgr1 defect did not show any synergistic effect on the quantum yield of photosystem II in crr2-2, a mutant in which NDH (NAD(P)H dehydrogenase) activity was impaired. Furthermore, the simultaneous determination of the quantum yields of both photosystems indicated that the ratio of linear and PSI cyclic electron transport was not significantly affected in pgr1. All the results indicated that the pgr1 mutation did not affect PGR5-dependent PQ reduction by Fd. The phenotypic differences between pgr1 and pgr5 indicate that maintenance of the proper balance of linear and PSI cyclic electron transport is essential for preventing over-reduction of the stroma.
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PMID:The pgr1 mutation in the Rieske subunit of the cytochrome b6f complex does not affect PGR5-dependent cyclic electron transport around photosystem I. 1595 30

Three biological activities of 12 soy isoflavones were investigated in terms of the structure-activity relationship. Seven molecular descriptors and one absorption predictor were significantly related to the inhibition of cytochrome P4501 activity in HepG2 cells by soy isoflavones, yielding water solubility [correlation coefficient (gamma)=-0.779] and hydrophobicity (gamma=0.718) as more relevant molecular properties. By contrast, the inducing activities of 12 soy isoflavones both on quinone reductase in HepG2 cells and proliferation of the osteoblastic MG-63 cells demonstrated significant correlation to the hydroxyl and methoxyl substituents on the isoflavone skeleton (p<0.01).
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PMID:Molecular and absorption properties of 12 soy isoflavones and their structure-activity relationship with selected biological activities. 1613 60

3-Nitrobenzanthrone (3-NBA) is a potent mutagen and potential human carcinogen identified in diesel exhaust and ambient air particulate matter. Previously, we detected the formation of 3-NBA-derived DNA adducts in rodent tissues by 32P-postlabeling, all of which are derived from reductive metabolites of 3-NBA bound to purine bases, but structural identification of these adducts has not yet been reported. We have now prepared 3-NBA-derived DNA adduct standards for 32P-postlabeling by reacting N-acetoxy-3-aminobenzanthrone (N-Aco-ABA) with purine nucleotides. Three deoxyguanosine (dG) adducts have been characterised as N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone-3'-phosphate (dG3'p-C8-N-ABA), 2-(2'-deoxyguanosin-N2-yl)-3-aminobenzanthrone-3'-phosphate (dG3'p-N2-ABA) and 2-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone-3'-phosphate (dG3'p-C8-C2-ABA), and a deoxyadenosine (dA) adduct was characterised as 2-(2'-deoxyadenosin-N6-yl)-3-aminobenzanthrone-3'-phosphate (dA3'p-N6-ABA). 3-NBA-derived DNA adducts formed experimentally in vivo and in vitro were compared with the chemically synthesised adducts. The major 3-NBA-derived DNA adduct formed in rat lung cochromatographed with dG3'p-N2-ABA in two independent systems (thin layer and high-performance liquid chromatography). This is also the major adduct formed in tissue of rats or mice treated with 3-aminobenzanthrone (3-ABA), the major human metabolite of 3-NBA. Similarly, dG3'p-C8-N-ABA and dA3'p-N6-ABA cochromatographed with two other adducts formed in various organs of rats or mice treated either with 3-NBA or 3-ABA, whereas dG3'p-C8-C2-ABA did not cochromatograph with any of the adducts found in vivo. Utilizing different enzymatic systems in vitro, including human hepatic microsomes and cytosols, and purified and recombinant enzymes, we found that a variety of enzymes [NAD(P)H:quinone oxidoreductase, xanthine oxidase, NADPH:cytochrome P450 oxidoreductase, cytochrome P450s 1A1 and 1A2, N,O-acetyltransferases 1 and 2, sulfotransferases 1A1 and 1A2, and myeloperoxidase] are able to catalyse the formation of 2-(2'-deoxyguanosin-N2-yl)-3-aminobenzanthrone, N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone and 2-(2'-deoxyadenosin-N6-yl)-3-aminobenzanthrone in DNA, after incubation with 3-NBA and/or 3-ABA.
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PMID:Identification of three major DNA adducts formed by the carcinogenic air pollutant 3-nitrobenzanthrone in rat lung at the C8 and N2 position of guanine and at the N6 position of adenine. 1633 2

The present study is an effort to identify a potent chemopreventive agent against various diseases (including cancer) in which oxidative stress plays an important causative role. Here, we investigated the effect of a hydroalcoholic (80% ethanol: 20% distilled water) extract of aerial roots of Tinospora cordifolia (50 and 100mg/kg body wt./day for 2 weeks) on carcinogen/drug metabolizing phase-I and phase-II enzymes, antioxidant enzymes, glutathione (GSH) content, lactate dehydrogenase and lipid peroxidation in liver of 8-week-old Swiss albino mice. The modulatory effect of the extract was also examined on extrahepatic organs, i.e., lung, kidney and forestomach, for the activities of GSH S-transferase (GST), DT-diaphorase (DTD), superoxide dismutase (SOD) and catalase. Significant increases in the levels of acid-soluble sulfhydryl (-SH) and cytochrome P(450) contents, and enzyme activities of cytochrome P(450) reductase, cytochrome b(5) reductase, GST, DTD, SOD, catalase, GSH peroxidase (GPX) and GSH reductase (GR) were observed in the liver. Both treated groups showed decreased malondialdehyde (MDA) formation. In lung SOD, catalase and GST; in kidney SOD and catalase; and in forestomach SOD, DTD and GST showed significant increase at both dose levels of treatment. BHA (0.75%, w/w in diet), a pure antioxidant compound, was used as a positive control. This group showed increase in hepatic levels of GSH content, cytochrome b(5), DTD, GST, GR and catalase, whereas MDA formation was inhibited significantly. In the BHA-treated group, the lung and kidney showed increased levels of catalase, DTD and GST, whereas SOD was significantly increased in the kidney and forestomach; the latter also showed an increase in the activities of DTD and GST. The enhanced GSH level and enzyme activities involved in xenobiotic metabolism and maintaining antioxidant status of cells are suggestive of a chemopreventive efficacy of T. cordifolia against chemotoxicity, including carcinogenicity, which warrants further investigation of active principle (s) present in the extract responsible for the observed effects employing various carcinogenesis models.
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PMID:Tinospora cordifolia induces enzymes of carcinogen/drug metabolism and antioxidant system, and inhibits lipid peroxidation in mice. 1636 Sep 36


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