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Biodegradation of 3,5-dinitrosalicylic acid by Phanerochaete chrysosporium

100%
Madaj R., Kalinowska H., Sroczyński W., Szeląg J., Sobiecka E.
Acta Universitatis Lodziensis. Folia Biologica et Oecologica
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2018
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vol. 14
14-22
PL
Związki nitrowe to szeroka grupa ksenobiotyków, które ze względu na swoją silną toksyczność, wyjątkową odporność na rozkład biologiczny oraz skłonność do bioakumulacji, stanowią bardzo poważny problem dla biosfery. Prowadzi się obecnie wiele badań nad mikroorganizmami, które zdołały wykształcić szlaki metaboliczne pozwalające na rozkład takich związków jak 2,4,6-trinitrotoluen, kwas pikrynowy czy kwas 3,5-dinitrosalicylowy. Jednym z takich mikroorganizmów jest podstawczak Phanerochaete chrysosporium, należący do grupy grzybów białej zgnilizny drewna. Artykuł ten poświęcony jest badaniom nad rozkładem kwasu 3,5-dinitrosalicylowego przez P. chrysosporium w warunkach hodowli stacjonarnej w pożywce zawierającej 0,05–0,5% masowego kwasu 3,5-dinitrosalicylowego. Uzyskane wyniki wskazują na zdolność wybranego mikroorganizmu do rozkładu substratu na drodze redukcji grup nitrowych.
EN
Despite intensive efforts put on prevention of environment pollution by nitroaromatic compounds, these xenobiotics have not been eliminated from the biosphere. The physicochemical properties make nitroaromatics extremely recalcitrant to biodegradation. Therefore, microbial degraders of these pollutants are sought after. This paper reports preliminary results of the study on degradation of 3,5-dinitrosalicylic acid (DNS) by a basidiomycetous fungus Phanerochaete chrysosporium under stationary conditions in a culture medium containing 0.05–0.5% v/v of DNS. The results obtained suggest that the fungus degrades DNS through the reductive pathway.
2
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Reduction of nitroaromatic compounds by NAD(P)H:quinone oxidoreductase (NQO1): the role of electron-accepting potency and structural parameters in the substrate specificity

88%
Misevičienė L., Anusevičius Ž., Šarlauskas J., Čėnas N.
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2006
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vol. 53
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issue 3
569-576
EN
We aimed to elucidate the role of electronic and structural parameters of nitroaromatic compounds in their two-electron reduction by NAD(P)H:quinone oxidoreductase (NQO1, DT-diaphorase, EC 1.6.99.2). The multiparameter regression analysis shows that the reactivity of nitroaromatic compounds (n = 38) increases with an increase in their single-electron reduction potential and the torsion angle between nitrogroup(s) and the aromatic ring. The binding efficiency of nitroaromatics in the active center of NQO1 exerted a less evident role in their reactivity. The reduction of nitroaromatics is characterized by more positive entropies of activation than the reduction of quinones. This points to a less efficient electronic coupling of nitroaromatics with the reduced isoalloxazine ring of FAD, and may explain their lower reactivity as compared to quinones. Another important but poorly understood factor enhancing the reactivity of nitroaromatics is their ability to bind at the dicumarol/quinone binding site in the active center of NQO1.
3
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Quinone- and nitroreductase reactions of Thermotoga maritima thioredoxin reductase

88%
Valiauga B., Rouhier N., Jacquot J.-P., Čėnas N.
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EN
The Thermotoga maritima NADH:thioredoxin reductase (TmTR) contains FAD and a catalytic disulfide in the active center, and uses a relatively poorly studied physiological oxidant Grx-1-type glutaredoxin. In order to further assess the redox properties of TmTR, we used series of quinoidal and nitroaromatic oxidants with a wide range of single-electron reduction potentials (E17, -0.49-0.09 V). We found that TmTR catalyzed the mixed single- and two-electron reduction of quinones and nitroaromatic compounds, which was much faster than the reduction of Grx-1. The reactivity of both groups of oxidants increased with an increase in their E17, thus pointing to the absence of their structural specificity. The maximal rates of quinone reduction in the steady-state reactions were lower than the maximal rates of reduction of FAD by NADH, obtained in presteady-state experiments. The mixed-type reaction inhibition by NAD+ was consistent with its competition for a NADH binding site in the oxidized enzyme form, and also with the reoxidation of the reduced enzyme form. The inhibition data yielded a value of the standard potential for TmTR of -0.31±0.03 V at pH 7.0, which may correspond to the FAD/FADH2 redox couple. Overall, the mechanism of quinone- and nitroreductase reactions of T. maritima TR was similar to the previously described mechanism of Arabidopsis thaliana TR, and points to their prooxidant and possibly cytotoxic role.
4
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Single-electron reduction of quinone and nitroaromatic xenobiotics by recombinant rat neuronal nitric oxide synthase

75%
Anusevičius Ž., Nivinskas H., Šarlauskas J., Sari M.-A., Boucher J.-L., Čėnas N.
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2013
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vol. 60
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issue 2
217-222
EN
We examined the kinetics of single-electron reduction of a large number of structurally diverse quinones and nitroaromatic compounds, including a number of antitumour and antiparasitic drugs, and nitroaromatic explosives by recombinant rat neuronal nitric oxide synthase (nNOS, EC 1.14.13.39), aiming to characterize the role of nNOS in the oxidative stress-type cytotoxicity of the above compounds. The steady-state second-order rate constants (kcat/Km) of reduction of the quinones and nitroaromatics varied from 102 M-1s-1 to 106 M-1s-1, and increased with an increase in their single-electron reduction potentials (E17). The presence of Ca2+/calmodulin enhanced the reactivity of nNOS. These reactions were consistent with an 'outer sphere' electron-transfer mechanism, considering the FMNH./FMNH2 couple of nNOS as the most reactive reduced enzyme form. An analysis of the reactions of nNOS within the 'outer sphere' electron-transfer mechanism gave the approximate values of the distance of electron transfer, 0.39-0.47 nm, which are consistent with the crystal structure of the reductase domain of nNOS. On the other hand, at low oxygen concentrations ([O2] = 40-50 μM), nNOS performs a net two-electron reduction of quinones and nitroaromatics. This implies that NOS may in part be responsible for the bioreductive alkylation by two-electron reduced forms of antitumour aziridinyl-substituted quinones under a modest hypoxia.
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