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Query: EC:3.4.23.17 (PCE)
 1,301 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of various doses (0.005-2.0 mg/kg b.w.) of vinblastine sulfate (VBL) was studied on the induction of micronuclei in polychromatic and normochromatic erythrocytes (PCE, NCE) of the bone marrow of female BALB/c mice. VBL treatment resulted in a dose-dependent increase in the frequency of micronucleated PCE and NCE, while the PCE/NCE ratio and mitotic index declined with increasing drug dose. The dose-effect curves were linear quadratic for all the parameters studied.
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PMID:Vinblastine treatment induces dose-dependent increases in the frequency of micronuclei in mouse bone marrow. 137 42

The kinetics of the previously reported paired basic residue-specific pro-opiomelanocortin-converting enzyme from bovine pituitary intermediate lobe secretory vesicles (Loh, Y. P., Parish, D.C., and Tuteja, R. (1985) J. Biol. Chem. 260, 7194-7205) were studied using human 125I-beta-lipotropin as substrate. The enzyme, at a concentration of 20 ng/100 microliters cleaved human beta-lipotropin to yield gamma-lipotropin, a beta-melanotropin linked to beta-endorphin intermediate and beta-endorphin, whereas at an enzyme concentration of 40 ng/100 microliters, the substrate was completely cleaved to yield beta-endorphin and beta-melanotropin. These products were identified by their immunological properties and size on sodium dodecyl sulfate-polyacrylamide gels. The 125I-beta-endorphin product was further shown by high pressure liquid chromatography to contain two forms; the major form co-eluted with 125I-Arg0-beta h-endorphin and the minor form with 125I-beta h-endorphin. No COOH-terminal shortened forms of beta-endorphin were detected. The products formed indicate cleavages at two of the three pairs of basic residues of human beta-lipotropin, at Lys37-Lys38 and Lys57-Arg58, but not at Lys86-Lys87. The cleavage at Lys57-Arg58 occurred primarily in between these basic residues. The Km values for the cleavage of the Lys37-Lys38 and Lys57-Arg58 pairs were 1.9 and 2.5 microM, respectively. The Vmax values for the cleavage of the Lys37-Lys38 and Lys58-Arg58 pairs were 4.8 nmol/micrograms of enzyme/h and 9.1 nmol/micrograms of enzyme/h, respectively.
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PMID:Kinetic studies on the processing of human beta-lipotropin by bovine pituitary intermediate lobe pro-opiomelanocortin-converting enzyme. 301 55

Dehalospirillum multivorans is a strictly anaerobic bacterium that is able to dechlorinate tetrachloroethene (perchloroethylene; PCE) via trichloroethene (TCE) to cis-1,2-dichloroethene (DCE) as part of its energy metabolism. The present communication describes some features of the dechlorination reaction in growing cultures, cell suspensions, and cell extracts of D. multivorans. Cell suspensions catalyzed the reductive dechlorination of PCE with pyruvate as electron donor at specific rates of up to 150 nmol (chloride released) min-1 (mg cell protein)-1 (300 microM PCE initially, pH 7.5, 25 degrees C). The rate of dechlorination depended on the PCE concentration; concentrations higher than 300 microM inhibited dehalogenation. The temperature optimum was between 25 and 30 degrees C; the pH optimum at about 7.5. Dehalogenation was sensitive to potential alternative electron acceptors such as fumarate or sulfur; nitrate or sulfate had no significant effect on PCE reduction. Propyl iodide (50 microM) almost completely inhibited the dehalogenation of PCE in cell suspensions. Cell extracts mediated the dehalogenation of PCE and of TCE with reduced methyl viologen as the electron donor at specific rates of up to 0.5 mumol (chloride released) min-1 (mg protein).-1 An abiotic reductive dehalogenation could be excluded since cell extracts heated for 10 min at 95 degrees C were inactive. The PCE dehalogenase was recovered in the soluble cell fraction after ultracentrifugation. The enzyme was not inactivated by oxygen.
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PMID:Tetrachloroethene metabolism of Dehalospirillum multivorans. 780 45

Tetrachloroethylene (PCE) is a toxic compound essentially used as a degreasing and dry-cleaning solvent. A methanogenic and sulfate-reducing consortium that dechlorinates and mineralizes high concentrations of PCE was derived from anaerobically digested sludge obtained from a waste water treatment plant (Bourg-en-Bresse, France). A methanogenic bacterium, strain FR, was isolated from this acclimated consortium. On the basis of morphological and physiological characteristics, strain FR was classified in the genus of Methanosarcina. Phylogeny analysis with the 16S rRNA gene sequence revealed that strain FR is highly related to Methanosarcina mazei and Methanosarcina frisia (99.6 and 99.5% identity, respectively). High concentrations (50-87 microM) of PCE were completely dechlorinated by strain FR cultures at the rate of 76 nM-mg protein(-1).day(-1). PCE dechlorination produced a nonidentified compound. The tracer experiments with [13C]PCE revealed that the product was nonchlorinated. Dechlorination of PCE to trichloroethylene was still active in the presence of boiled cell extract of the strain FR. However, no further dechlorination was observed. This result suggests that a cofactor rather than an enzymatic system is responsible for the first dechlorination of PCE. Dechlorination-active fractions purified from cell extracts on a XAD-4 column revealed the presence of F(420), F(430), and cobamides cofactors. This is the first report of the isolation of a methanogenic bacterium with the ability to dechlorinate high concentrations of PCE to a nonchlorinated product.
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PMID:Isolation of a methanogenic bacterium, Methanosarcina sp. strain FR, for its ability to degrade high concentration of perchloroethylene. 1038 26

This study demonstrates the ability of Desulfitobacterium spp. to utilize aliphatic sulfonates as terminal electron acceptors (TEA) for growth. Isethionate (2-hydroxyethanesulfonate) reduction by Desulfitobacterium hafniense resulted in acetate as well as sulfide accumulation in accordance with the expectation that the carbon portion of isethionate was oxidized to acetate and the sulfur was reduced to sulfide. The presence of a polypeptide, approximately 97 kDa, was evident in isethionate-grown cells of Desulfitobacterium hafniense, Desulfitobacterium sp. strain PCE 1, and the two sulfate-reducing bacteria (SRB)-Desulfovibrio desulfuricans IC1 (T. J. Lie, J. R. Leadbetter, and E. R. Leadbetter, Geomicrobiol. J. 15:135-149, 1998) and Desulfomicrobium norvegicum; this polypeptide was not detected when these bacteria were grown on TEA other than isethionate, suggesting involvement in its metabolism. The sulfate analogs molybdate and tungstate, effective in inhibiting sulfate reduction by SRB, were examined for their effects on sulfonate reduction. Molybdate effectively inhibited sulfonate reduction by strain IC1 and selectively inhibited isethionate (but not cysteate) reduction by Desulfitobacterium dehalogenans and Desulfitobacterium sp. strain PCE 1. Desulfitobacterium hafniense, however, grew with both isethionate and cysteate in the presence of molybdate. In contrast, tungstate only partially inhibited sulfonate reduction by both SRB and Desulfitobacterium spp. Similarly, another inhibitor of sulfate reduction, 1,8-dihydroxyanthraquinone, effectively inhibited sulfate reduction by SRB but only partially inhibited sulfonate reduction by both SRB and Desulfitobacterium hafniense.
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PMID:Sulfonates as terminal electron acceptors for growth of sulfite-reducing bacteria (Desulfitobacterium spp.) and sulfate-reducing bacteria: effects of inhibitors of sulfidogenesis. 1050 97

The effects of surfactants, sodium dodecyl sulfate (SDS) and Triton X-a00 (TX), and alcohols (methanol, ethanol, and propanol) on the dehalogenation of TCE and PCE by zero-valent iron were examined. Surface concentrations of PCE and TCE on the iron were dependent on aqueous surfactant concentrations. At concentrations above the CMC, sorbed halocarbon concentrations declined and concentrations associated with solution phase micelles increased. The anionic surfactant SDS ([SDS] < CMC) did not affect reduction rates, until the CMC was exceeded after which reactivity decreased, possibly due to sequestering of the TCE and PCE in mobile micelles. The nonionic TX showed a mixed effect on reactivity, increasing the PCE reduction rate, but not affecting TCE removal. Production of TCE from PCE increased in the presence of TX. Similar experiments showed that methanol, ethanol, and propanol inhibited reduction of TCE and PCE by metallic iron. Zero-valent iron may be useful in recycling soil washing effluents contaminated with TCE and PCE.
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PMID:Effects of alcohols, anionic and nonionic surfactants on the reduction of PCE and TCE by zero-valent iron. 1131 92

The dissolved hydrogen concentrations under various redox processes were investigated based on batch experiments. Chloroethenes including tetrachloroethene (PCE), cis-dichloroethene (cis-DCE) and vinylchloride (VC) were respectively used as culture substrates. For each chloroethene, a series of bottles were prepared with the additions of different electron acceptors or donors such as nitrate, manganese oxide, ferrous iron, sulfate, carbondioxide and volatile fatty acids. Hydrogen concentrations as well as redox species were measured over time to ensure the achievements of characteristic hydrogen levels in various enrichment batches. The results showed that redox processes with nitrate, manganese oxide and ferric iron as the electron acceptors exhibited hydrogen threshold values close to PCE/TCE dechlorination, whereas cis-DCE and VC dechlorinations exhibited hydrogen threshold values in the range of sulfate reduction and methanogenesis, respectively. Characteristic hydrogen concentrations for various redox processes were as follows (nM): denitrification, 0.1-0.4; manganese reduction, 0.1-2.0; iron reduction, 0.1-0.4; sulfate reduction, 1.5-4.5; methanogenesis, 2.5-24; PCE/TCE dechlorination, 0.6-0.9; eis-DCE dechlorination, 0.1-2.5; and VC dechlorination, 2-24.
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PMID:Characteristic hydrogen concentrations for various redox processes in batch study. 1168 86

Tetrachloroethene (PCE) dehalorespiration was investigated in a continuous coculture of the sulfate-reducing bacterium Desulfovibrio fructosivorans and the dehalorespiring Desulfitobacterium frappieri TCE1 at different sulfate concentrations and in the absence of sulfate. Fructose (2.5 mM) was the single electron donor, which could be used only by the sulfate reducer. With 2.5 mM sulfate, the dehalogenating strain was outnumbered by the sulfate-reducing bacterium, sulfate reduction was the dominating process, and only trace amounts of PCE were dehalogenated by strain TCE1. With 1 mM sulfate in the medium, complete sulfate reduction and complete PCE dehalogenation to cis-dichloroethene (cis-DCE) occurred. In the absence of sulfate, PCE was also completely dehalogenated to cis-DCE, and the population size of strain TCE1 increased significantly. The results presented here describe for the first time dehalogenation of PCE by a dehalorespiring anaerobe in strict dependence on the activity of a sulfate-reducing bacterium with a substrate that is exclusively used by the sulfate reducer. This interaction was studied under strictly controlled and quantifiable conditions in continuous culture and shown to depend on interspecies hydrogen transfer under sulfate-depleted conditions. Interspecies hydrogen transfer was demonstrated by direct H(2) measurements of the gas phase and by the production of methane after the addition of a third organism, Methanobacterium formicicum.
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PMID:Tetrachloroethene dehalorespiration and growth of Desulfitobacterium frappieri TCE1 in strict dependence on the activity of Desulfovibrio fructosivorans. 1182 2

Chlorinated ethenes are pollutants in contaminated soil and groundwater, and one of the efficient way to remove them is biodegradation. In this paper, the microbial breakdown of PCE, cis-DCE and VC with initial concentrations of 100 mumol/L were studied under different redox conditions at temperature 20 degrees C. The results showed that in the presence of ferric iron and carbon dioxide, PCE were dechlorinated to TCE (0.26/day) and cis-DCE (0.31/day), respectively. In the presence of fatty acids and without competition from inorganic electron acceptors, all the studied chlorinated compounds were completely dechlorinated to ethenes. However, the degradation rates of cis-DCE and VC (0.04/day) were much lower than that of PCE (0.57/day). Under denitrifying, manganese reducing and sulfate reducing conditions, no degradation of chloroethenes was observed. When the temperature was lowered to 12 degrees C, the activities of dechlorinating microbes were also reduced, nevertheless, the completely reductive dechlorination of chloroethenes still occurred.
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PMID:[Dechlorination of chlorinated ethenes under different redox conditions]. 1204 14

A sediment column study was carried out to demonstrate the bioremediation of chloroethene- and nickel-contaminated sediment in a single anaerobic step under sulfate-reducing conditions. Four columns (one untreated control column and three experimental columns) with sediment from a chloroethene- and nickel-contaminated site were investigated for 1 year applying different treatments. By stimulating the activity of sulfate-reducing bacteria by the addition of sulfate as supplementary electron acceptor, complex anaerobic communities were maintained with lactate as electron donor (with or without methanol), which achieved complete dehalogenation of tetra- and trichloroethenes (PCE and TCE) to ethene and ethane. A few weeks after sulfate addition, production of sulfide increased, indicating an increasing activity of sulfate-reducing bacteria. The nickel concentration in the effluent of one nickel-spiked column was greatly reduced, likely due to the enhanced sulfide production, causing precipitation of nickel sulfide. At the end of the study, 94% of the initial amount of nickel added to that column was recovered in the sediment As compared to the untreated (nonspiked) control column, all chloroethene-spiked columns ladditions of PCE and TCE) showed a permanent release of small chloride ion quantities (approximately 0.5-0.7 mM chloride), which were detected in the effluents a few weeks after sulfide production was observed for the first time. The formation of ethene and ethane as final products after dechlorination of PCE and TCE was detected in some effluents and in some gas phases of the columns. Other metabolites or intermediates (such as DCE isomers) were only detected sporadically in negligible quantities. The results of this study demonstrated thatmicrobial activity stimulated under sulfate-reducing conditions can have a beneficial effect on both the precipitation of heavy metals and the complete dechlorination of organochlorines. The strongly negative redox potential created by the activity of sulfate-reducing bacteria may be one factor responsible for stimulating the activity of the dehalogenating bacteria in the test columns.
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PMID:Dehalogenation of chlorinated ethenes and immobilization of nickel in anaerobic sediment columns under sulfidogenic conditions. 1209 58


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