Generation of reactive oxygen species during the enzymatic oxidation of polycyclic aromatic hydrocarbon trans-dihydrodiols catalyzed by dihydrodiol dehydrogenase
Generation of reactive oxygen species during the enzymatic oxidation of polycyclic aromatic hydrocarbon trans-dihydrodiols catalyzed by dihydrodiol dehydrogenase
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DOI：
10.1021/tx950055s
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发表时间：
1996-01-01
影响因子：
4.1
通讯作者：
Harvey, RG
中科院分区：
文献类型：
--
作者：
Penning, TM;Ohnishi, ST;Harvey, RG
二氢二醇脱氢酶（DD; EC 1.3.1.20）催化多环芳烃（PAH）反式二氢二醇（近似致癌物）氧化为儿茶酚，儿茶酚迅速自氧化生成邻醌（Smithgall, t.e., Harvey, r.g., and Penning, t.m., 1988）。化学263,1814-1820)。虽然这一途径抑制了多环芳烃抗和辛二醇环氧化物（最终致癌物）的形成，但预计自氧化过程会产生活性氧（ROS）。我们现在证明了NADP（+）依赖于均相DD催化的(+/-)-反式-1,2-二羟基-1,2-二氢萘（Npdiol）和(+/-)-反式-7,8-二羟基-7,8-二氢苯并[a]芘（Bpdiol）的氧化伴随着分子氧的消耗和H2O2的产生。在这两种反式二氢二醇底物中，氧气消耗与H2O2生成的化学计量量与反应一致：QH(2) + O-2 = H2O2 + Q，其中QH(2)为儿茶酚，Q为邻醌。以Npdiol或Bpdiol为底物，DD催化了超氧阴离子的产生，可以通过检测被超氧化物歧化酶抑制的血细胞还原速率来检测。以5,5-二甲基-1-吡咯啉n-氧化物（DMPO）为自旋捕获剂，在Npdiol和Bpdiol的酶促氧化过程中形成了与DMPO- ch3相对应的自旋加合物。CH3的形成。自由基由OH生成。以二甲氧基甲苯为助溶剂，对其进行攻击。这些自旋加合物被超氧化物歧化酶和过氧化氢酶削弱，这表明O-2（-）和H2O2是形成DMPO-CH3的必需条件。有人提出，O-2（-）是进行自氧化的自由基，生成的H2O2经过芬顿化学反应生成OH。激进。用超氧阴离子生成体系（次黄嘌呤/黄嘌呤氧化酶）和DMPO作为自旋捕获剂，在DMSO存在下观察到相同的自旋加合物。在多环芳烃反式二氢二醇（近似致癌物）氧化过程中，DD产生ROS的能力可能对肿瘤的发生和促进具有重要意义。
Dihydrodiol dehydrogenase (DD; EC 1.3.1.20) catalyzes the oxidation of polycyclic aromatic hydrocarbon (PAH) trans-dihydrodiols (proximate carcinogens) to catechols which rapidly autoxidize to yield o-quinones (Smithgall, T. E., Harvey, R. G., and Penning, T. M. (1988) J. Biol. Chem 263, 1814-1820). Although this pathway suppresses the formation of the PAH anti- and syn-diol epoxides (ultimate carcinogens), the process of autoxidation is anticipated to yield reactive oxygen species (ROS). We now show that the NADP(+) dependent oxidation of (+/-)-trans-1,2-dihydroxy-1,2-dihydronaphthalene (Npdiol) and (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (Bpdiol) catalyzed by homogeneous DD is accompanied by the consumption of molecular oxygen and the production of H2O2. With both trans-dihydrodiol substrates, oxygen consumption was stoichiometric with H2O2 production consistent with the reaction: QH(2) + O-2 = H2O2 + Q, where QH(2) is the catechol and Q is the o-quinone. Using Npdiol or Bpdiol as substrates, a burst of superoxide anion production is catalyzed by DD which can be detected as the rate of cyt c reduction that is inhibited by superoxide dismutase. Using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as spin-trapping agent, secondary spin adducts corresponding to DMPO-CH3 were formed during the enzymatic oxidation of Npdiol and Bpdiol. The formation of the CH3. radical arises from the OH. attack of DMSO, which was used as cosolvent. These spin adducts were attenuated by superoxide dismutase and catalase, implying that O-2(-.) and H2O2 are obligatory for the formation of DMPO-CH3. It is proposed that O-2(-.) is the radical that propagates autoxidation and that the resultant H2O2 undergoes Fenton chemistry to produce the OH. radical. Identical spin adducts were observed using a superoxide anion generating system (hypoxanthine/xanthine oxidase) and DMPO as spin-trapping agent in the presence of DMSO. The ability of DD to generate ROS during the oxidation of PAH trans-dihydrodiols (proximate carcinogens) may have important implications for tumor initiation and promotion.