Fetzner S
Carl von Ossietzky-Universität Oldenburg, Germany.
Appl Microbiol Biotechnol. 1998 Dec;50(6):633-57. doi: 10.1007/s002530051346.
Halogenated organic compounds are produced industrially in large quantities and represent an important class of environmental pollutants. However, an abundance of haloorganic compounds is also produced naturally. Bacteria have evolved several strategies for the enzyme-catalyzed dehalogenation and degradation of both haloaliphatic and haloaromatic compounds: (i) Oxidative dehalogenation is the result of mono- or dioxygenase-catalyzed, co-metabolic or metabolic reactions. (ii) In dehydrohalogenase-catalyzed dehalogenation, halide elimination leads to the formation of a double bond. (iii) Substitutive dehalogenation in most cases is a hydrolytic process, catalyzed by halidohydrolases, but there also is a "thiolytic" mechanism with glutathione as cosubstrate. Dehalogenation by halohydrin hydrogen-halide lyases is the result of an intramolecular substitution reaction. (iv) A distinct dechlorination mechanism involves methyl transfer from chloromethane onto tetrahydrofolate. (v) Reductive dehalogenations are co-metabolic processes, or they are specific reactions involved in substrate utilization (carbon metabolism), or reductive dehalogenation is coupled to energy conservation: some anaerobic bacteria use a specific haloorganic compound as electron acceptor of a respiratory process. This review discusses the mechanisms of enzyme-catalyzed dehalogenation reactions, describes some pathways of the bacterial degradation of haloorganic compounds, and indicates some trends in the biological treatment of organohalogen-polluted air, groundwater, soil, and sediments.
卤代有机化合物在工业上大量生产，是一类重要的环境污染物。然而，大量的卤代有机化合物也是天然产生的。细菌已经进化出多种酶催化卤代脂肪族和卤代芳香族化合物脱卤和降解的策略：（i）氧化脱卤是单加氧酶或双加氧酶催化的共代谢或代谢反应的结果。（ii）在脱氢卤化酶催化的脱卤反应中，卤化物消除导致双键的形成。（iii）在大多数情况下，取代脱卤是一个水解过程，由卤代水解酶催化，但也有一种以谷胱甘肽为共底物的“硫解”机制。卤代醇卤化氢裂解酶催化的脱卤是分子内取代反应的结果。（iv）一种独特的脱氯机制涉及氯甲烷上的甲基转移到四氢叶酸上。（v）还原脱卤是共代谢过程，或者是底物利用（碳代谢）中涉及的特定反应，或者还原脱卤与能量守恒相关：一些厌氧细菌使用特定的卤代有机化合物作为呼吸过程的电子受体。本文综述了酶催化脱卤反应的机制，描述了细菌降解卤代有机化合物的一些途径，并指出了有机卤污染空气、地下水、土壤和沉积物生物处理的一些趋势。
