Yoon S J, Koh Y H, Floyd R A, Park J W
Department of Biochemistry, College of Natural Sciences, Kyungpook National University, Taegu, South Korea.
Mutat Res. 2000 Mar 14;448(1):97-104. doi: 10.1016/s0027-5107(00)00005-1.
Oxidative DNA damage caused by a cysteine metal-catalyzed oxidation system (Cys-MCO) comprised of Fe(3+), O(2), and a cysteine as an electron donor was enhanced by copper, zinc superoxide dismutase (CuZnSOD) in a concentration-dependent manner, as reflected by the formation of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) and strand breaks. Unlike CuZnSOD, manganese SOD (MnSOD) as well as iron SOD (FeSOD) did not enhance DNA damage. The capacity of CuZnSOD to enhance damage to DNA was inhibited by a spin-trapping agent, 5, 5-dimethyl-1-pyrroline N-oxide (DMPO) and a metal chelator, diethylenetriaminepentaacetic acid (DETAPAC). The deoxyribose assay showed that hydroxyl free radicals were generated in the reaction of CuZnSOD with Cys-MCO. We found that the Cys-MCO system caused the release of free copper from CuZnSOD. CuZnSOD also caused the two-fold enhancement of a mutation in the pUC18 lacZ' gene in the presence of Cys-MCO when measured as a loss of alpha-complementation. Based on these results, we interpret the effects of CuZnSOD on Cys-MCO-induced DNA damage and mutation as due to reactive oxygen species, probably hydroxyl free radicals, formed by the reaction of free Cu(2+), released from oxidatively damaged CuZnSOD, and H(2)O(2) produced by the Cys-MCO system.
由铁（III）、氧气和作为电子供体的半胱氨酸组成的半胱氨酸金属催化氧化系统（Cys-MCO）所引起的氧化性DNA损伤，会被铜锌超氧化物歧化酶（CuZnSOD）以浓度依赖的方式增强，这可通过8-羟基-2'-脱氧鸟苷（8-OH-dG）的形成和链断裂来反映。与CuZnSOD不同，锰超氧化物歧化酶（MnSOD）以及铁超氧化物歧化酶（FeSOD）不会增强DNA损伤。CuZnSOD增强对DNA损伤的能力会被自旋捕获剂5,5-二甲基-1-吡咯啉N-氧化物（DMPO）和金属螯合剂二乙烯三胺五乙酸（DETAPAC）抑制。脱氧核糖分析表明，在CuZnSOD与Cys-MCO的反应中会产生羟基自由基。我们发现Cys-MCO系统会导致CuZnSOD释放游离铜。当以α-互补性丧失来衡量时，在存在Cys-MCO的情况下，CuZnSOD还会使pUC18 lacZ'基因中的突变增强两倍。基于这些结果，我们将CuZnSOD对Cys-MCO诱导的DNA损伤和突变的影响解释为是由于活性氧物种，可能是羟基自由基，由氧化损伤的CuZnSOD释放的游离铜（2+）与Cys-MCO系统产生的H₂O₂反应形成。
