Behroozi S J, Kim W, Dannaldson J, Gates K S
Department of Chemistry, University of Missouri-Columbia 65211, USA.
Biochemistry. 1996 Feb 13;35(6):1768-74. doi: 10.1021/bi952257t.
Leinamycin is a recently discovered, thiol-dependent DNA-cleaving natural product. The mechanism of DNA cleavage by leinamycin is unknown. Inspired by this intriguing natural product, we have investigated the DNA-cleaving properties of three 1,2-dithiolan-3-one 1-oxides (1-3) that are structurally related to the suspected DNA-cleaving "core" of leinamycin. It was found that, similar to leinamycin, these three 1,2-dithiolan-3-one 1-oxides are thiol-dependent DNA-cleaving agents. At the concentrations of 1-3 used in these experiments (approximately 100 microM), efficient DNA cleavage is absolutely dependent on added thiol, with optimum cleavage occurring at 5-10 equiv (500 microM-1 mM) of added thiol. 2-Mercaptoethanol, glutathione, dithiothreitol, and thiophenol function with approximately equal efficiency as triggering agents for the cleavage reaction. DNA cleavage by 1-3 is not highly pH-dependent. Cleavage of DNA by these sulfur heterocycles is diminished by the removal of molecular oxygen from the reaction medium, by the radical scavengers methanol, ethanol, and mannitol, and by the enzyme catalase. Superoxide dismutase does not suppress DNA cleavage by these compounds. When diethylenetriaminepentaacetic acid is employed in these reactions as a chelator of adventitious trace metal ions, DNA cleavage is efficiently inhibited. The S-deoxy analog of 1 does not cleave DNA under conditions where 1 effects efficient thiol-mediated cleavage of DNA. These experiments indicate that, in concert with thiols, 1,2-dithiolan-3-one 1-oxides convert molecular oxygen to DNA-cleaving oxygen radicals. The marked effect of catalase further suggests that molecular oxygen is converted to hydrogen peroxide which ultimately cleaves DNA via a trace metal-dependent Fenton reaction. This work demonstrates that 1,2-dithiolan-3-one 1-oxides represent a general class of thiol-potentiated DNA-cleaving molecules.
链黑霉素是一种最近发现的、依赖硫醇的DNA切割天然产物。链黑霉素切割DNA的机制尚不清楚。受这种有趣的天然产物启发，我们研究了三种与链黑霉素疑似DNA切割“核心”结构相关的1,2 - 二硫杂环戊烷 - 3 - 酮1 - 氧化物（1 - 3）的DNA切割特性。结果发现，与链黑霉素类似，这三种1,2 - 二硫杂环戊烷 - 3 - 酮1 - 氧化物是依赖硫醇的DNA切割剂。在这些实验中使用的1 - 3浓度（约100微摩尔）下，有效的DNA切割绝对依赖于添加的硫醇，在添加5 - 10当量（500微摩尔 - 1毫摩尔）硫醇时发生最佳切割。2 - 巯基乙醇、谷胱甘肽、二硫苏糖醇和苯硫酚作为切割反应的引发剂，其作用效率大致相同。1 - 3对DNA的切割对pH值的依赖性不强。这些硫杂环对DNA的切割会因从反应介质中去除分子氧、自由基清除剂甲醇、乙醇和甘露醇以及过氧化氢酶而减弱。超氧化物歧化酶不会抑制这些化合物对DNA的切割。当在这些反应中使用二乙三胺五乙酸作为偶然痕量金属离子的螯合剂时，DNA切割会被有效抑制。1的S - 脱氧类似物在1能有效进行硫醇介导的DNA切割的条件下不会切割DNA。这些实验表明，与硫醇协同作用时，1,2 - 二硫杂环戊烷 - 3 - 酮1 - 氧化物将分子氧转化为切割DNA的氧自由基。过氧化氢酶的显著作用进一步表明，分子氧被转化为过氧化氢，最终通过痕量金属依赖的芬顿反应切割DNA。这项工作表明，1,2 - 二硫杂环戊烷 - 3 - 酮1 - 氧化物代表了一类普遍的硫醇增强型DNA切割分子。
