Comparative transcriptome analysis reveals the mechanism underlying 3,5-dibromo-4-hydroxybenzoate catabolism via a new oxidative-decarboxylation pathway
Comparative transcriptome analysis reveals the mechanism underlying 3,5-dibromo-4-hydroxybenzoate catabolism via a new oxidative-decarboxylation pathway
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比较转录组分析揭示了 3,5-二溴-4-羟基苯甲酸酯通过新的氧化脱羧途径分解代谢的机制
DOI：
10.1128/aem.02467-17
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发表时间：
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影响因子：
4.4
通讯作者：
ong Jiang
中科院分区：
文献类型：
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作者：
Kai Chen;Yang Mu;Shanshan Jian;Xiaoxia Zang;Qing Chen;Weibin Jia;Zhuang Ke;Yanzheng Gao;Ji;ong Jiang
化合物3，5-二溴-4-羟基苯甲酸酯（DBHB）在环境中既可通过生物降解释放，也可自然产生，其环境归宿备受关注。好氧和厌氧还原脱卤是DBHB催化的仅有的两种途径。在这项研究中，一个新的氧化脱羧DBHB催化剂的途径被确定在一个DBHB利用菌株Pigmentiphaga sp. H8。基于比较转录组分析和随后的实验验证，阐明了该途径的遗传决定因素。由orf420-orf426组成的基因簇在DBHB诱导的细胞中的转录比未诱导的细胞中的转录上调约33~4400倍，被怀疑参与DBHB催化。odcA（orf420）基因是DBHB初始催化所必需的，其编码一种新的NAD（P）H依赖性黄素单加氧酶，其介导DBHB氧化脱羧为2，6-二溴氢醌（2，6-DBHQ）。纯化的OdcA的底物特异性表明，4-羟基及其邻位卤素对于OdcA对1-位点羧基的羟基化是重要的。然后，2，6-DBHQ被双加氧酶OdcB（Orf 425）环切割成2-溴马来酰乙酸，其最终被马来酰乙酸还原酶OdcC（Orf 426）转化成β-酮己二酸。这些结果提供了一个更好的理解卤化对羟基苯甲酸酯的分解代谢多样性的分子机制。
The compound 3,5-dibromo-4-hydroxybenzoate (DBHB) is both anthropogenically released into and naturally produced in the environment, and its environmental fate is of great concern. Aerobic and anaerobic reductive dehalogenations are the only two reported pathways for DBHB catabolism. In this study, a new oxidative-decarboxylation pathway for DBHB catabolism was identified in a DBHB-utilizing strain of Pigmentiphaga sp. H8. The genetic determinants underlying this pathway were elucidated based on comparative transcriptome analysis and subsequent experimental validation. A gene cluster comprising orf420-orf426, with transcripts that were about 33~4400-fold up-regulated in DBHB-induced cells compared with those in uninduced cells, was suspected to be involved in DBHB catabolism. The gene odcA (orf420), which is essential for the initial catabolism of DBHB, encodes a novel NAD(P)H-dependent flavin monooxygenase that mediates the oxidative decarboxylation of DBHB to 2,6-dibromohydroquinone (2,6-DBHQ). The substrate specificity of the purified OdcA indicated that the 4-hydroxyl group and its ortho-halogen(s) are important for hydroxylation of the 1-site carboxyl group by OdcA. Then, 2,6-DBHQ is ring-cleaved by the dioxygenase OdcB (Orf425) to 2-bromomaleylacetate, which is finally transformed to β-ketoadipate by the maleylacetate reductase OdcC (Orf426). These results provide a better understanding of the molecular mechanism underlying the catabolic diversity of halogenated para-hydroxybenzoates.