Janssen Dick B, Dinkla Inez J T, Poelarends Gerrit J, Terpstra Peter
Biochemical Laboratory, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands.
Environ Microbiol. 2005 Dec;7(12):1868-82. doi: 10.1111/j.1462-2920.2005.00966.x.
Bacterial dehalogenases catalyse the cleavage of carbon-halogen bonds, which is a key step in aerobic mineralization pathways of many halogenated compounds that occur as environmental pollutants. There is a broad range of dehalogenases, which can be classified in different protein superfamilies and have fundamentally different catalytic mechanisms. Identical dehalogenases have repeatedly been detected in organisms that were isolated at different geographical locations, indicating that only a restricted number of sequences are used for a certain dehalogenation reaction in organohalogen-utilizing organisms. At the same time, massive random sequencing of environmental DNA, and microbial genome sequencing projects have shown that there is a large diversity of dehalogenase sequences that is not employed by known catabolic pathways. The corresponding proteins may have novel functions and selectivities that could be valuable for biotransformations in the future. Apparently, traditional enrichment and metagenome approaches explore different segments of sequence space. This is also observed with alkane hydroxylases, a category of proteins that can be detected on basis of conserved sequence motifs and for which a large number of sequences has been found in isolated bacterial cultures and genomic databases. It is likely that ongoing genetic adaptation, with the recruitment of silent sequences into functional catabolic routes and evolution of substrate range by mutations in structural genes, will further enhance the catabolic potential of bacteria toward synthetic organohalogens and ultimately contribute to cleansing the environment of these toxic and recalcitrant chemicals.
细菌脱卤酶催化碳 - 卤键的断裂，这是许多作为环境污染物的卤代化合物有氧矿化途径中的关键步骤。脱卤酶种类繁多，可分为不同的蛋白质超家族，且具有根本不同的催化机制。在不同地理位置分离出的生物体中反复检测到相同的脱卤酶，这表明在利用有机卤化物的生物体中，特定的脱卤反应仅使用有限数量的序列。与此同时，环境DNA的大规模随机测序以及微生物基因组测序项目表明，存在大量未被已知分解代谢途径利用的脱卤酶序列。相应的蛋白质可能具有新的功能和选择性，这对未来的生物转化可能很有价值。显然，传统的富集和宏基因组方法探索的是序列空间的不同部分。在烷烃羟化酶中也观察到了这一点，烷烃羟化酶是一类可根据保守序列基序检测到的蛋白质，在分离的细菌培养物和基因组数据库中已发现大量此类序列。持续的基因适应，即将沉默序列纳入功能性分解代谢途径以及通过结构基因突变扩大底物范围，可能会进一步增强细菌对合成有机卤化物的分解代谢潜力，并最终有助于清除环境中的这些有毒且难降解的化学物质。
