Biochemistry of the Anaerobic Dehalogenation of Chlorinated Aromatics

RagsdaleEPA列出的20种最危险的化合物包括10种卤化有机化合物。厌氧生物在这类化合物的自然生物降解中很可能是非常重要的，并显示出对受卤化物污染的场所进行生物修复的前景。已经有关于能够代谢多氯联苯、杀虫剂和除草剂的联合体的研究。最近发现的脱硫杆菌或脱硫素类的成员可以在称为脱卤素呼吸的能量产生过程中快速有效地去除烷基卤化物和芳基卤化物的卤素基团。这是一种还原脱卤化反应，其中一个电子供体(丙酮酸、氢气等)通过电子转移链减少烷基或芳基卤化物，有效地用氢化物当量取代氯化物。这是对这类生物和相关酶的研究的早期阶段。该项目旨在更好地了解脱卤芳烃的还原脱卤化过程。到目前为止，已经分离出了几种脱盐呼吸微生物。已纯化了两个芳基氯脱卤酶，并克隆了编码其中一个的基因。关于这类酶的机理研究很少。这里概述的研究将提供关于这类相对较新的酶反应的新信息。编码脱卤酶(S)的基因将被克隆、测序和过度表达。将对脱卤酶(S)进行表征，并阐明其还原脱卤化机理(S)。这些酶似乎含有亚铁血红素或维生素B12。这代表了这些金属中心的新角色，这一点将被阐明。将进行光谱和电化学研究，以确定和确定这些修复基团在脱卤化过程中的作用。这些研究可能会产生重大的生物技术影响。来自这些生物体的生物体或酶可用于生物修复过程。这里描述的研究旨在确定哪些生物体和这些生物体中的哪些酶最有可能成为被多氯联苯污染的生物修复场所，并用于植物生物技术。将评估生物和纯化酶的活性，以确定它们在芳香环的邻位、间位和对位上的脱卤化能力，以及还原脱卤化异生物质(如芳草胺)和除草剂(如敌草畏和2，4-D)的能力。

RagsdaleThe EPA list of the twenty most hazardous compounds includes ten halogenated organic compounds. Anaerobic organisms are likely to be very important in the natural biodegradation of such compounds and show promise for bioremediation of sites contaminated with halogenated compounds. There have been studies of consortia that can metabolize polychlorinated biphenyls (PCBs), pesticides, and herbicides. Members of the recently discovered Desulfitobacterium or Desulfomonile class can rapidly and efficiently remove the halogen group of alkyl halides and aryl halides in an energy yielding process called dehalorespiration. This is a reductive dehalogenation in which an electron donor (pyruvate, H2, etc.) reduces the alkyl or aryl halide through an electron transfer chain, effectively replacing the chloride with a hydride equivalent. This is an early stage in research on such organisms and the relevant enzymes. This project is aimed at better understanding the process of reductive dehalogenation of dehalogenated aromatics. So far several dehalorespiring organisms have been isolated. Two aryl chloride dehalogenases have been purified and the gene encoding one of these has been cloned. There have been few mechanistic studies of such enzymes. The research outlined here will provide new information about this relatively new class of enzymatic reactions. The genes encoding the dehalogenase(s) will be cloned, sequenced and overexpressed. The dehalogenase(s) will be characterized and the reductive dehalogenation mechanism(s) will be elucidated. The enzymes appear to contain either heme or vitamin B12. This represents a new role for these metal centers, which will be elucidated. Spectroscopic and electrochemical studies will be performed to identify and determine the roles of these prosthetic groups in the dehalogenation process. There could be significant biotechnological impact of these studies. The organisms or enzymes from these organisms could be used in bioremediation processes. Research described here aims to determine which organisms and which enzymes from these organisms show the most potential for bioremediating sites contaminated with PCBs and for use in plant biotechnology. The activities of the organisms and purified enzymes will be assessed for their ability to dehalogenate at the ortho, meta, and para positions of the aromatic ring and to reductively dehalogenate xenobiotics like Aroclor and herbicides like dicamba and 2,4-D.