Biochemistry of the Anaerobic Dehalogenation of Chlorinated Aromatics

环保署列出的20种最危险的化合物中包括10种卤化有机化合物。厌氧生物在这些化合物的自然生物降解中可能是非常重要的，并且在被卤代化合物污染的场所的生物修复中显示出希望。有研究表明，联合体可以代谢多氯联苯（PCBs）、杀虫剂和除草剂。最近发现的Desulfitobacterium或Desulfomonile类的成员可以在称为脱卤呼吸的能量生成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。这是一种还原性脱卤反应，其中电子供体（丙酮酸酯，H2等）通过电子转移链还原烷基或芳基卤化物，有效地用等价的氢化物取代氯化物。这是对这类生物和相关酶研究的早期阶段。本项目旨在更好地了解脱卤芳烃的还原脱卤过程。到目前为止，已经分离出了几种脱盐呼吸生物。纯化了两个芳基氯脱卤酶，并克隆了其中一个的编码基因。对这类酶的机理研究很少。这里概述的研究将为这类相对较新的酶促反应提供新的信息。编码脱卤酶的基因将被克隆、测序和过表达。对脱卤酶进行了表征，并阐明了还原脱卤的机理。这些酶似乎含有血红素或维生素B12。这代表了这些金属中心的新作用，这将得到阐明。将进行光谱和电化学研究，以识别和确定这些假体基团在脱卤过程中的作用。这些研究可能会产生重大的生物技术影响。这些生物或来自这些生物的酶可用于生物修复过程。本文所述的研究旨在确定哪些生物和来自这些生物的哪些酶最有可能修复被多氯联苯污染的场所并用于植物生物技术。生物和纯化酶的活性将评估其在芳香环的邻位、间位和对位上脱卤的能力，以及还原除卤的能力，如芳香烃和除草剂，如麦草畏和2,4- d。

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.