As a typical brominated flame retardants (BFRs), 2,4,6-tribromophenol (TBP) has serious hazard to the environmental health and its environmental fate has attracted considerable attention. Dehalogenation reaction plays key role in microbial TBP degradation and detoxification. So far, several halophenols-degrading enzymes have been reported to transform their substrate by oxidative dehalogenation; however, the molecular and biochemistry characterization of microbial hydrolytic dehalogenation is limited. In this study, Cupriavidus sp. CNP-8 with high TBP degradation activity was found to degrade TBP via an obviously differnet pathway as compared to other reported TBP-degraders. The transcription of hnp genes were significantly upregulated with TBP stimulation, indicating their involvment in TBP degradation. Enzymatic assays with ¹⁸O-labeling experiments showed that HnpAB, a two-component FAD-dependent monooxygenase, transformed TBP via consecutive oxidative and hydrolytic debromination reactions with the formation of 6-bromo-1,2,4-benzenetriol (BBT) as the ring-cleavage substrate. The function of the BBT ring-cleavage enzyme (HnpC) was also characterized both in vitro and in vivo. This finding provides new molecular mechanism of microbial detoxification of TBP and novel information of the environmental fate of this BFRs. Furthermore, to investigate the frequency of this novel dehalogenation mechanism in microbes, we also analyzed the distribution as well as the genetic structure of the hnpABC cluster by comparative genomics. Although hnpA homolog is distributed in several bacterial genera including Cupriavidus, Paraburkholderia, Variovorax and Streptomyces, the complete hnpABC cluster is only retrieved from Cupriavidus and strictly conservative in the genomes. This indicated that Cupriavidus have unique evolutionary pattern in acquiring the hnpABC to degrade TBP and its analogs, enhancing our understanding of the microbial adaptive evolution in halophenols-contaminated environment.

作为典型的溴化阻燃剂（BFRs），2,4,6-三溴苯酚（TBP）对环境健康具有严重危害，其环境归宿已引起广泛关注。脱卤反应在微生物TBP降解和解毒中起关键作用。到目前为止，已经报道了几种卤代酚降解酶通过氧化脱卤来转化它们的底物。然而，微生物水解脱卤的分子和生物化学表征是有限的。在这项研究中， Cupriavidus sp。与其他报道的 TBP 降解剂相比，发现具有高 TBP 降解活性的 CNP-8 通过明显不同的途径降解 TBP。hnp的转录基因在 TBP 刺激下显着上调，表明它们参与 TBP 降解。^{具有18 个}O 标记实验的酶促测定表明，HnpAB 是一种双组分 FAD 依赖性单加氧酶，通过连续的氧化和水解脱溴反应转化 TBP，形成 6-溴-1,2,4-苯三醇 (BBT) 作为解环底物。BBT 环裂解酶 (HnpC) 的功能也在体外和体内进行了表征. 这一发现提供了 TBP 微生物解毒的新分子机制和该 BFR 的环境归宿的新信息。此外，为了研究这种新型脱卤机制在微生物中的频率，我们还通过比较基因组学分析了hnpABC簇的分布和遗传结构。尽管hnpA同源物分布在几个细菌属中，包括Cupriavidus、Paraburkholderia、Variovorax和Streptomyces，但完整的hnpABC簇仅从Cupriavidus中检索到并且在基因组中严格保守。这表明Cupriavidus在获得hnpABC以降解 TBP 及其类似物方面具有独特的进化模式，增强了我们对卤代酚污染环境中微生物适应性进化的理解。