Enzymes involved in the anaerobic degradation of meta-substituted halobenzoates
Enzymes involved in the anaerobic degradation of meta-substituted halobenzoates
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DOI：
10.1111/j.1365-2958.2011.07856.x
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发表时间：
2011-11-01
影响因子：
3.6
通讯作者：
Boll, Matthias
中科院分区：
文献类型：
--
作者：
Kuntze, Kevin;Kiefer, Patrick;Boll, Matthias
有机卤化物是与环境相关的化合物，可被好氧和厌氧微生物降解。在厌氧条件下，具有反硝化作用的绿藻能够作为唯一的碳源和能量源降解卤苯甲酸盐。基于LC-MS/ ms的辅酶A （CoA）硫酯分析表明，3-氯或3-溴苯甲酰辅酶A降解途径的非卤代辅酶A酯中间体优先代谢3-氯或3-溴苯甲酰辅酶A。相反，不支持生长的3-氟苯甲酸酯被转化为脱芳化氟化辅酶a酯终端产品。在3-氯/3-溴苯甲酸酯上生长的细胞提取物催化Ti(III)-柠檬酸盐和atp依赖的3-氯/3-溴苯甲酰辅酶a还原脱卤为苯甲酰辅酶a，而3-氟苯甲酰辅酶a转化为氟化环二烯基辅酶a化合物。还原脱卤反应被确定为存在于所有兼性厌氧芳香族化合物降解细菌中atp依赖的I类苯甲酰辅酶a还原酶（BCR）的未知活性。提出了一种两步脱芳化/氢卤化物消除机理。鉴定了一种卤苯甲酸羧酸辅酶A连接酶；然而，没有这种酶存在于Thauera aromatica中，它不能生长在卤苯甲酸盐上。总之，似乎存在一个卤代苯甲酸盐特异性羧酸辅酶a连接酶而不是一个特定的还原脱卤酶决定芳香化合物降解厌氧菌是否能够代谢卤代苯甲酸盐。
Organohalides are environmentally relevant compounds that can be degraded by aerobic and anaerobic microorganisms. The denitrifying Thauera chlorobenzoica is capable of degrading halobenzoates as sole carbon and energy source under anaerobic conditions. LC-MS/MS-based coenzyme A (CoA) thioester analysis revealed that 3-chloro- or 3-bromobenzoate were preferentially metabolized via non-halogenated CoA-ester intermediates of the benzoyl-CoA degradation pathway. In contrast, 3-fluorobenzoate, which does not support growth, was converted to dearomatized fluorinated CoA ester dead-end products. Extracts from cells grown on 3-chloro-/3-bromobenzoate catalysed the Ti(III)-citrate- and ATP-dependent reductive dehalogenation of 3-chloro/3-bromobenzoyl-CoA to benzoyl-CoA, whereas 3-fluorobenzoyl-CoA was converted to a fluorinated cyclic dienoyl-CoA compound. The reductive dehalogenation reactions were identified as previously unknown activities of ATP-dependent class I benzoyl-CoA reductases (BCR) present in all facultatively anaerobic, aromatic compound degrading bacteria. A two-step dearomatization/H-halide elimination mechanism is proposed. A halobenzoate-specific carboxylic acid CoA ligase was characterized in T. chlorobenzoica; however, no such enzyme is present in Thauera aromatica, which cannot grow on halobenzoates. In conclusion, it appears that the presence of a halobenzoate-specific carboxylic acid CoA ligase rather than a specific reductive dehalogenase governs whether an aromatic compound degrading anaerobe is capable of metabolizing halobenzoates.