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Preliminary characteristic of quinone binding site on ferredoxin: NADPplus oxidoreductase molecule

100%

Grzyb J., Bojko M., Waloszek A., Latowski D., Wieckowski S.

Polish Journal of Natural Sciences. Supplement

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2003

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tom 01

2

Single-electron reduction of quinone and nitroaromatic xenobiotics by recombinant rat neuronal nitric oxide synthase

75%

Anusevicius Z., Nivinskas H., Sarlauskas J., Sari M.-A., Boucher J.-L., Cenas N.

Acta Biochimica Polonica

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2013

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tom 60

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nr 2

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.

3

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Polyphenol-protein complexes and their consequences for the redox activity, structure and function of honey. A current view and new hypothesis - a review

63%

Brudzynski K., Maldonado-Alvarez L.

Polish Journal of Food and Nutrition Sciences

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2015

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tom 65

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nr 2

There is increasing evidence that protein complexation by honey polyphenols is changing honey structure and function. This relatively less investigated filed of honey research is presented in a context of known mechanism of formation of the stable polyphenol-protein complexes in other foods. At a core of these interactions lies the ability of polyphenols to form non-covalent and covalent bonds with proteins leading to transient and/or irreversible complexes, respectively. Honey storage and thermal processing induces non-enzymatic oxidation of polyphenols to reactive quinones and enables them to form covalent bonds with proteins. In this short review, we present data from our laboratory on previously unrecognized types of protein-polyphenol complexes that differed in size, stoichiometry, and antioxidant capacities, and the implications they have to honey antioxidant and antibacterial activities. Our intent is to provide a current understanding of protein-polyphenol complexation in honey and also some new thoughts /hypotheses that can be useful in directing future research.

4

Two-electron reduction of quinones by Enterobacter cloacae PB2 pentaerythritol tetranitrate reductase: quantitative structure-activity relationships

63%

Miseviciene L., Anusevicius Z., Sarlauskas J., Harris R. J., Scrutton N. S., Cenas N.

Acta Biochimica Polonica

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2007

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tom 54

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nr 2

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.

5

Effect of plant o-dihydroxyphenols and quinone on generation of reactive oxygen species within the grain aphid tissues

51%

Lukasik I., Golawska S.

Pestycydy

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2008

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nr 3-4

117-124

Effect of some dietary o-dihydroxyphenols and quinones on hydrogen peroxide (H2O2) concentration within tissues of the grain aphid Sitobion avenae (F.) (Homoptera, Aphididae) has been studied. Among the studied aphid morphs the highest level of H2O2 total was noted for winged adults (alatae) and the lowest for larvae. The aphids exposed to the dietary pro-oxidative o-dihydroxyphenols demonstrated significantly higher concentration of hydrogen peroxide than the control ones. Among the studied compounds, caffeic acid showed the strongest effect on the H2O2 level within the aphid tissues. The highest concentration (0.1%) of this phenolic acid caused above 2-fold increase in the content of this radical within the grain aphid tissues. The significance of these results for understanding the toxicity of phenols to cereal aphids is discussed.

6

Inhibition of A.castellanii uncoupling protein activity by GTP depends on the redox state of quinone

51%

Swida A., Czarna M., Antos N., Raczynska M., Jarmuszkiewicz W.

Biological Letters

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2005

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tom 42

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nr 2 Spec.Vol.

7

Zmiany aktywnosci antyoksydacyjnej [plus] katechiny w wyniku utleniania enzymatycznego

45%

Sosnowska D.

Żywność Nauka Technologia Jakość. Suplement

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2000

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tom 07

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nr 3

69-76

(+) katechina wykazuje cenne właściwości biologiczne, jest efektywnym zmiataczem wolnych rodników. W pracy badano wpływ enzymatycznego utleniania (+) katechiny na jej aktywność anty oksydacyjną. Proces utleniania (+) katechiny prowadzono przy udziale polifenolooksydazy (PPO) i tyrozynazy w pH 4 i 7. Aktywność anty oksydacyjną badanych roztworów określano dwoma metodami polegającymi na zmiataniu rodników: DPPH i ABTS. Zmiany zawartości (+) katechiny oraz produkty jej degradacji rejestrowano metodą HPLC i TLC. Szybkość utleniania (+) katechiny była wyższa w obecności PPO niż tyrozynazy. Obniżenie pH środowiska reakcyjnego z 7 do 4 powodowało zmniejszenie szybkości utleniania katechiny. Dwugodzinne utlenianie katechiny (PPO w pH 7) powodowało spadek zawartości tego monomeru o 57% i pojawienie się dimerów i tetramerów. Natomiast efektywność zmiatania stabilnego rodnika DPPH obniżyła się o 25% a ABTS tylko o 12%, co może sugerować, że produkty enzymatycznego utleniania (+) katechiny wykazują pewną aktywność anty oksydacyjną w stosunku do tych rodników.

Ograniczanie wyników

Preliminary characteristic of quinone binding site on ferredoxin: NADPplus oxidoreductase molecule

Single-electron reduction of quinone and nitroaromatic xenobiotics by recombinant rat neuronal nitric oxide synthase

Polyphenol-protein complexes and their consequences for the redox activity, structure and function of honey. A current view and new hypothesis - a review

Two-electron reduction of quinones by Enterobacter cloacae PB2 pentaerythritol tetranitrate reductase: quantitative structure-activity relationships

Effect of plant o-dihydroxyphenols and quinone on generation of reactive oxygen species within the grain aphid tissues

Inhibition of A.castellanii uncoupling protein activity by GTP depends on the redox state of quinone

Zmiany aktywnosci antyoksydacyjnej [plus] katechiny w wyniku utleniania enzymatycznego