Activation of Methyl-substituted Benzenes in Anaerobic Bacteria

微生物酶，特别是厌氧微生物的酶，正受到人们的极大关注，因为它们为各种天然催化剂提供了宝贵的来源。特别令人感兴趣的是那些催化相对不活跃的有机化合物转化的酶。甲苯、二甲苯和三甲基苯等甲基取代苯相对稳定，是地下汽油储罐泄漏和地面泄漏排放到环境中的重要饮用水污染物。为了深入了解甲苯厌氧活化的机理，已分离出几种不同的甲苯厌氧矿化微生物，并对其进行了更详细的研究。这些研究表明，甲苯厌氧代谢的初始反应是甲苯甲基与富马酸的加成反应生成丁二酸苄酯。催化这一反应的苄基琥珀酸合成酶(BSS)是一类新的甲苯活化酶的原型。最近的研究有力地表明，BSS是一种自由基酶，它携带着必需的甘氨酰自由基。利用光谱以及生化和遗传学研究，本项目将调查BSS反应中的自由基参与，并研究BSS的激活方式。本项目将加深我们对微生物降解代表饮用水重要污染物的高稳定有机化合物的途径的理解。这些信息应该有助于开发有效的生物手段，从水中去除这些污染物。

Microbial enzymes, specifically those of anaerobic microbes, are receiving significant attention because they provide an invaluable source for diverse natural catalysts. Of particular interest are those enzymes that catalyze the transformation of relatively unreactive organic compounds. Methyl-substituted benzenes, such as toluene, xylenes, and trimethylbenzenes, are relatively stable and represent important drinking water contaminants that are released into the environment from leaking underground gasoline storage tanks and surface spills. Several diverse, anaerobic, toluene--mineralizing microbes have been isolated and studied in more detail to gain insight into the mechanism of anaerobic activation of toluene. These studies showed that the initial reaction of anaerobic toluene metabolism is the addition of the toluene methyl group to fumarate to form benzylsuccinate. Benzylsuccinate synthase (BSS), which catalyzes this reaction, is emerging as a prototype of a new class of enzymes for activation of methylbenzenes. Recent studies strongly suggest that BSS is a radical enzyme, which carries an essential glycyl radical. Using spectroscopic as well as biochemical and genetic studies, this project will investigate the involvement of a radical in the BSS reaction and examine the mode of BSS activation.This project will further our understanding of the pathways used by microbes to degrade highly stable organic compounds that represent important contaminants of drinking water. This information should help in developing effective biological means of removing these contaminants from water.