Molecular characterization of the enzymes involved in the degradation of a brominated aromatic herbicide
Molecular characterization of the enzymes involved in the degradation of a brominated aromatic herbicide
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DOI：
10.1111/mmi.12332
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发表时间：
2013-09-01
影响因子：
3.6
通讯作者：
Jiang, Jiandong
中科院分区：
文献类型：
--
作者：
Chen, Kai;Huang, Linglong;Jiang, Jiandong
脱卤是卤代芳烃降解的关键步骤，而还原脱卤在好氧菌中很少发生。在这项研究中，一个好氧菌株Comamonas sp. 7 D-2被证明可以完全降解溴代芳香族除草剂溴苯腈，并在好氧条件下释放两个当量的溴化物。对参与溴苯腈降解为4-羧基-2-羟基粘康酸-6-半醛的酶（腈水解酶、还原性脱卤酶（BhbA）、4-羟基苯甲酸3-单加氧酶和原儿茶酸4，5-双加氧酶）进行了分子鉴定。新的脱卤酶BhbA被证明是一个呼吸连接的还原性脱卤酶（RdhA）结构域和NAD（P）H依赖性氧化还原酶结构域的复合物，并具有厌氧呼吸RdhA的关键特征，包括两个预测的[4Fe-4S]簇结合基序和与疏水膜蛋白（BhbB）的密切关联。证实了BhbB将BhbA锚在膜上。BhbA被部分纯化，并发现使用NAD（P）H作为电子供体。全长bhbA同源物几乎只在海洋好氧变形菌中发现，这表明还原脱卤广泛发生在好氧菌和bhbA是从海洋微生物水平转移。在需氧菌中发现的功能性还原脱卤酶和开环加氧酶为基础研究以及生物修复的潜在应用开辟了可能性。
Dehalogenation is the key step in the degradation of halogenated aromatics, while reductive dehalogenation is originally thought to rarely occur in aerobes. In this study, an aerobic strain of Comamonas sp. 7D-2 was shown to degrade the brominated aromatic herbicide bromoxynil completely and release two equivalents of bromides under aerobic conditions. The enzymes involved in the degradation of bromoxynil to 4-carboxy-2-hydroxymuconate-6-semialdehyde, including nitrilase, reductive dehalogenase (BhbA), 4-hydroxybenzoate 3-monooxygenase and protocatechuate 4,5-dioxygenase, were molecularly characterized. The novel dehalogenase BhbA was shown to be a complex of a respiration-linked reductive dehalogenase (RdhA) domain and a NAD(P)H-dependent oxidoreductase domain and to have key features of anaerobic respiratory RdhAs, including two predicted binding motifs for [4Fe-4S] clusters and a close association with a hydrophobic membrane protein (BhbB). BhbB was confirmed to anchor BhbA to the membrane. BhbA was partially purified and found to use NAD(P)H as electron donors. Full-length bhbA homologues were found almost exclusively in marine aerobic proteobacteria, suggesting that reductive dehalogenation occurs extensively in aerobes and that bhbA is horizontally transferred from marine microorganisms. The discovery of a functional reductive dehalogenase and ring-cleavage oxygenases in an aerobe opens up possibilities for basic research as well as the potential application for bioremediation.