Wackett L P
Department of Biochemistry, University of Minnesota, St. Paul 55108, USA.
Ann N Y Acad Sci. 1998 Dec 13;864:142-52. doi: 10.1111/j.1749-6632.1998.tb10297.x.
Biocatalysis is important in both natural and engineered environments. The major global reactions in the biospheric cycling of carbon, nitrogen, and other elements are catalyzed by microorganisms. The global carbon cycle includes millions of organic compounds that are made by plants, microorganisms, and organic chemists. Most of those compounds are transformed by microbial enzymes. Degradative metabolism is known as catabolism and yields principally carbon dioxide, methane, or biomass. Microbial catabolic enzymes are a great resource for biotechnology. They are the building blocks for engineering novel metabolic pathways and evolving improved enzymes in the laboratory. Two multicomponent bacterial oxygeneases, cytochrome P450cam and toluene dioxygenase, catalyze the dechlorination of polyhalogenated C2 compounds. Seven genes encoding those functional enzyme complexes were coexpressed in a Pseudomonas and shown to metabolize pentachloreothane to nonhalogenated organic acids that were metabolized further to carbon dioxide. In another example, the enzyme catalyzing the dechlorination of the herbicide atrazine was subjected to iterative DNA shuffling to produce mutations. By using a plate screening assay, mutated atrazine chlorohydrolase that catalyzed a more rapid dechlorination of atrazine was obtained. The mutant genes were sequences and found to encode up to 11 amino acid changes. Atrazine chlorohydrolase is currently being used in a model municipal water treatment system to test the feasibility of using enzymes for atrazine decontamination. These data suggest that the natural diversity of bacterial catabolic enzymes provides the starting point for improved biocatalytic systems that meet the needs of commercial applications.
生物催化在自然环境和工程环境中都很重要。碳、氮和其他元素在生物圈循环中的主要全球反应是由微生物催化的。全球碳循环包括数百万种由植物、微生物和有机化学家制造的有机化合物。这些化合物中的大多数是由微生物酶转化的。降解代谢被称为分解代谢，主要产生二氧化碳、甲烷或生物质。微生物分解代谢酶是生物技术的重要资源。它们是构建新型代谢途径和在实验室中进化改良酶的基础。两种多组分细菌加氧酶，细胞色素P450cam和甲苯双加氧酶，催化多卤代C2化合物的脱氯反应。编码这些功能酶复合物的七个基因在假单胞菌中共表达，并显示可将五氯乙烷代谢为非卤代有机酸，这些有机酸可进一步代谢为二氧化碳。在另一个例子中，对催化除草剂阿特拉津脱氯的酶进行了迭代DNA改组以产生突变。通过平板筛选试验，获得了催化阿特拉津脱氯更快的突变阿特拉津氯水解酶。对突变基因进行了测序，发现其编码多达11个氨基酸的变化。阿特拉津氯水解酶目前正在一个示范城市水处理系统中使用，以测试使用酶去除阿特拉津污染的可行性。这些数据表明，细菌分解代谢酶的自然多样性为满足商业应用需求的改良生物催化系统提供了起点。
