Generation of Reactive Oxygen Species during the Enzymatic Oxidation of Polycyclic Aromatic Hydrocarbon trans-Dihydrodiols Catalyzed by Dihydrodiol Dehydrogenase
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- 作者：Trevor M. Penning ; S. Tsuyoshi Ohnishi ; Tomoki Ohnishi ; and Ronald G. Harvey
- 刊名：Chemical Research in Toxicology
- 出版年：1996
- 出版时间：January 1996
- 年：1996
- 卷：9
- 期：1
- 页码：84 - 92
- 全文大小：600K
- 年卷期：v.9,no.1(January 1996)
- ISSN：1520-5010
文摘
Dihydrodiol dehydrogenase (DD; EC 1.3.1.20) catalyzes theoxidation of polycyclic aromatichydrocarbon (PAH) trans-dihydrodiols (proximate carcinogens)to catechols which rapidlyautoxidize to yield o-quinones (Smithgall, T. E., Harvey, R.G., and Penning, T. M. (1988) J.Biol. Chem 263, 1814-1820). Although thispathway suppresses the formation of the PAHanti- and syn-diol epoxides (ultimatecarcinogens), the process of autoxidation is anticipatedto yield reactive oxygen species (ROS). We now show that theNADP+ dependent oxidation of(±)-trans-1,2-dihydroxy-1,2-dihydronaphthalene (Npdiol)and (±)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (Bpdiol) catalyzed byhomogeneous DD is accompanied by the consumptionof molecular oxygen and the production of H2O2.With both trans-dihydrodiol substrates,oxygenconsumption was stoichiometric with H2O2production consistent with the reaction: QH2+O2 = H2O2 + Q, whereQH2 is the catechol and Q is the o-quinone.Using Npdiol or Bpdiol assubstrates, a burst of superoxide anion production is catalyzed by DDwhich can be detectedas the rate of cyt c reduction that is inhibited bysuperoxide dismutase. Using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as spin-trapping agent, secondaryspin adducts corresponding toDMPO-CH3 were formed during the enzymatic oxidation ofNpdiol and Bpdiol. The formationof the CH3
radical arises from theOH attack of DMSO, which was used as cosolvent.Thesespin adducts were attenuated by superoxide dismutase and catalase,implying that O2-andH2O2 are obligatory for the formation ofDMPO-CH3. It is proposed thatO2- is theradicalthat propagates autoxidation and that the resultantH2O2 undergoes Fenton chemistrytoproduce the OH radical. Identical spin adducts wereobserved using a superoxide aniongenerating system (hypoxanthine/xanthine oxidase) and DMPO asspin-trapping agent in thepresence of DMSO. The ability of DD to generate ROS during theoxidation of PAH trans-dihydrodiols (proximate carcinogens) may have important implications fortumor initiationand promotion.
radical arises from theOH attack of DMSO, which was used as cosolvent.Thesespin adducts were attenuated by superoxide dismutase and catalase,implying that O2-andH2O2 are obligatory for the formation ofDMPO-CH3. It is proposed thatO2- is theradicalthat propagates autoxidation and that the resultantH2O2 undergoes Fenton chemistrytoproduce the OH radical. Identical spin adducts wereobserved using a superoxide aniongenerating system (hypoxanthine/xanthine oxidase) and DMPO asspin-trapping agent in thepresence of DMSO. The ability of DD to generate ROS during theoxidation of PAH trans-dihydrodiols (proximate carcinogens) may have important implications fortumor initiationand promotion.