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Wyszukujesz frazę "quinones" wg kryterium: Temat

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    Wyświetlanie 1-5 z 5
    Tytuł:
    Cytotoxicity of anticancer aziridinyl-substituted benzoquinones in primary mice splenocytes
    Autorzy:
    Miliukienė, Valė
    Nivinskas, Henrikas
    Čėnas, Narimantas
    Powiązania:
    https://bibliotekanauki.pl/articles/1039227.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    aziridinyl-substituted quinones
    cytotoxicity
    oxidative stress
    Opis:
    The anticancer activity of aziridinyl-quinones is mainly attributed to their NAD(P)H:quinone oxidoreductase 1 (NQO1)-catalyzed two-electron reduction into DNA-alkylating products. However, little is known about their cytotoxicity in primary cells, which may be important in understanding their side effects. We found that the cytotoxicity of aziridinyl-unsubstituted quinones (n = 12) in mice splenocytes with a low amount of NQO1, 4 nmol × mg-1 × min-1, was caused mainly by the oxidative stress. Aziridinyl-benzoquinones (n = 6) including a novel anticancer agent RH1 were more cytotoxic than aziridinyl-unsubstituted ones with the similar redox properties, and their cytotoxicity was not decreased by an inhibitor of NQO1, dicumarol. The possible reasons for their enhanced cytotoxicity are discussed.
    Źródło:
    Acta Biochimica Polonica; 2014, 61, 4; 833-836
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Two-electron reduction of quinones by Enterobacter cloacae PB2 pentaerythritol tetranitrate reductase: quantitative structure-activity relationships
    Autorzy:
    Misevičienė, Lina
    Anusevičius, Žilvinas
    Šarlauskas, Jonas
    Harris, Richard
    Scrutton, Nigel
    Čėnas, Narimantas
    Powiązania:
    https://bibliotekanauki.pl/articles/1041091.pdf
    Data publikacji:
    2007
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    pentaerythritol tetranitrate reductase
    reduction mechanism
    electron-transfer
    quinones
    Opis:
    In order to clarify the poorly understood mechanisms of two-electron reduction of quinones by flavoenzymes, we examined the quinone reductase reactions of a member of a structurally distinct old yellow enzyme family, Enterobacter cloacae PB2 pentaerythritol tetranitrate reductase (PETNR). PETNR catalyzes two-electron reduction of quinones according to a 'ping-pong' scheme. A multiparameter analysis shows that the reactivity of quinones increases with an increase in their single-electron reduction potential and pKa of their semiquinones (a three-step (e-,H+,e-) hydride transfer scheme), or with an increase in their hydride-transfer potential (E7(H-)) (a single-step (H-) hydride transfer scheme), and decreases with a decrease in their van der Waals volume. However, the pH-dependence of PETNR reactivity is more consistent with a single-step hydride transfer. A comparison of X-ray data of PETNR, mammalian NAD(P)H : quinone oxidoreductase (NQO1), and Enterobacter cloacae nitroreductase, which reduce quinones in a two-electron way, and their reactivity revealed that PETNR is much less reactive, and much less sensitive to the quinone substrate steric effects than NQO1. This may be attributed to the lack of π-π stacking between quinone and the displaced aromatic amino acid in the active center, e.g., with Phe-178' in NQO1.
    Źródło:
    Acta Biochimica Polonica; 2007, 54, 2; 379-385
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Quinone- and nitroreductase reactions of Thermotoga maritima thioredoxin reductase
    Autorzy:
    Valiauga, Benjaminas
    Rouhier, Nicolas
    Jacquot, Jean-Pierre
    Čėnas, Narimantas
    Powiązania:
    https://bibliotekanauki.pl/articles/1039108.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    thioredoxin reductase
    quinones
    nitroaromatic compounds
    oxidative stress
    Thermotoga
    Opis:
    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.
    Źródło:
    Acta Biochimica Polonica; 2015, 62, 2; 303-309
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Błędy w badaniach reakcji enzymatycznych wynikające z nieprzewidzianych reakcji utleniania-redukcji
    Errors in the studies of enzymatic reactions resulting from unforeseen oxidation-reduction reactions
    Autorzy:
    Gąsowska-Bajger, B.
    Wojtasek, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/142841.pdf
    Data publikacji:
    2014
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Przemysłu Chemicznego. Zakład Wydawniczy CHEMPRESS-SITPChem
    Tematy:
    oksydoreduktazy
    tyrozynaza
    peroksydaza
    o-chinony
    hydrazyna
    pterydyny
    oxidoreductases
    tyrosinase
    peroxidase
    o-quinones
    hydrazine
    pteridines
    Opis:
    Reakcje enzymatyczne są najczęściej monitorowane za pomocą pomiarów spektrofotometrycznych przy jednej długości fali. Jest to zwykle bezpieczne, gdy stosuje się tylko standardowy substrat dający znany produkt. Jeśli jednak bada się mieszaninę związków, np. substratu i potencjalnych inhibitorów, to mogą pojawić się poważne błędy. Często zachodzą bowiem wówczas niespodziewane reakcje. Potencjalne inhibitory same mogą być substratami enzymu, albo mogą reagować z produktem lub intermediatami przekształcania substratu. Spodziewany produkt może więc nie powstać, albo powstają produkty uboczne z widmami absorpcji zupełnie różnymi od oczekiwanego produktu lub też nakładającymi się na to widmo, co daje kompletnie fałszywe wyniki.
    Enzymatic reactions are usually monitored using spectrophotometric measurements at one wavelength. Such measurements usually pose no risk, if a standard substrate that gives known product is used. However, if a mixture of compounds is studied, e.g. a substrate and potential inhibitors, this may lead to serious errors. In such cases unexpected reactions often occur. The potential inhibitors might be themselves enzyme substrates or might react with the product or intermediates of substrate conversion. Therefore, the expected product might not be produced or by-products are formed with spectra completely differently from the expected product or overlapping with this spectrum what might give totally false results.
    Źródło:
    Chemik; 2014, 68, 4; 341-346
    0009-2886
    Pojawia się w:
    Chemik
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Single-electron reduction of quinone and nitroaromatic xenobiotics by recombinant rat neuronal nitric oxide synthase
    Autorzy:
    Anusevičius, Žilvinas
    Nivinskas, Henrikas
    Šarlauskas, Jonas
    Sari, Marie-Agnes
    Boucher, Jean-Luc
    Čėnas, Narimantas
    Powiązania:
    https://bibliotekanauki.pl/articles/1039577.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    antitumour agents
    nitroaromatic compounds
    electron transfer mechanism
    oxidative stress
    quinones
    Neuronal nitric oxide synthase (nNOS)
    Opis:
    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.
    Źródło:
    Acta Biochimica Polonica; 2013, 60, 2; 217-222
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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