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    Wyświetlanie 1-4 z 4
    Tytuł:
    Reduction of nitroaromatic compounds by NAD(P)H:quinone oxidoreductase (NQO1): the role of electron-accepting potency and structural parameters in the substrate specificity
    Autorzy:
    Misevičienė, Lina
    Anusevičius, Žilvinas
    Šarlauskas, Jonas
    Čėnas, Narimantas
    Powiązania:
    https://bibliotekanauki.pl/articles/1041217.pdf
    Data publikacji:
    2006
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    reduction potential
    DT-diaphorase
    nitroaromatic compounds
    reduction mechanism
    explosives
    Opis:
    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.
    Źródło:
    Acta Biochimica Polonica; 2006, 53, 3; 569-576
    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:
    Redox properties and prooxidant cytotoxicity of a neuroleptic agent 6,7-dinitrodihydroquinoxaline-2,3-dione (DNQX)
    Autorzy:
    Šarlauskas, Jonas
    Nemeikaitė-Čėnienė, Aušra
    Misevičienė, Lina
    Krikštopaitis, Kastis
    Anusevičius, Žilvinas
    Čėnas, Narimantas
    Powiązania:
    https://bibliotekanauki.pl/articles/1039581.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    flavoenzymes
    cytotoxicity
    DNQX
    oxidative stress
    Opis:
    In order to characterize the possible mechanism(s) of cytotoxicity of a neuroleptic agent 6,7-dinitrodihydroquinoxaline-2,3-dione (DNQX) we examined the redox properties of DNQX, and its mononitro- (NQX) and denitro- (QX) derivatives. The irreversible electrochemical reduction of the nitro groups of DNQX was characterized by the reduction peak potentials (Ep,7) of -0.43 V and -0.72 V vs. Ag/AgCl at pH 7.0, whereas NQX was reduced at Ep,7 = -0.67 V. The reactivities of DNQX and NQX towards the single-electron transferring enzymes NADPH:cytochrome P-450 reductase and NADPH:adrenodoxin reductase/adrenodoxin complex were similar to those of model nitrobenzenes with the single-electron reduction potential (E17) values of -0.29 V - -0.42 V. DNQX and NQX also acted as substrates for two-electron transferring mammalian NAD(P)H:quinone oxidoreductase (DT-diaphorase). The cytotoxicity of DNQX in bovine leukemia virus-transformed lamb kidney fibroblasts (line FLK) was prevented by antioxidants and an inhibitor of NQO1, dicoumarol, and was enhanced by the prooxidant alkylating agent 1,3-bis(2-chloromethyl)-1-nitrosourea. A comparison with model nitrobenzene compounds shows that the cytotoxicity of DNQX and NQX reasonably agrees with the ease of their electrochemical reduction, and/or their reactivities towards the used enzymatic single-electron reducing systems. Thus, our data imply that the cytotoxicity of DNQX in FLK cells is exerted mainly through oxidative stress.
    Źródło:
    Acta Biochimica Polonica; 2013, 60, 2; 227-231
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    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 1-4 z 4

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