Distinct Catalytic Behaviors between Two 1,4-Dioxane-Degrading Monooxygenases: Kinetics, Inhibition, and Substrate Range
Distinct Catalytic Behaviors between Two 1,4-Dioxane-Degrading Monooxygenases: Kinetics, Inhibition, and Substrate Range
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DOI：
10.1021/acs.est.9b05671
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发表时间：
2020-02-04
影响因子：
11.4
通讯作者：
Li, Mengyan
中科院分区：
文献类型：
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作者：
Li, Fei;Deng, Daiyong;Li, Mengyan
间接自然衰减（MNA）和工程生物修复已被公认为是有效和具有成本效益的原位处理，以减轻1，4-二氧六环（二氧六环）污染。二氧六环的代谢可由丙烷单加氧酶（PRM）和四氢呋喃单加氧酶（THM）启动，它们分别属于可溶性二铁单加氧酶家族的第6和第5族。在这项研究中，我们全面比较了PRM和THM在异源宿主耻垢分枝杆菌mc（2）-155中单独表达时的催化行为。动力学结果显示，PRM的半饱和系数（Km）为53.0 +/- 13.1 mg/L，比THM（235.8 +/- 61.6 mg/L）低近4倍，表明PRM对二氧六环具有更高的亲和力。暴露于三种常见的共污染物（1，1-二氯乙烯，三氯乙烯，和1，1，1-三氯乙烷）表明，PRM也比THM更耐其抑制。因此，表达PRM的二氧六环降解剂在受影响的位点可能比具有THM的那些在生理学和生态学上更有利，其中二氧六环浓度相对低（例如，250至1000微克/升），同时存在氯化溶剂（例如，0.5至8 mg/L），强调需要调查PRM和THM编码基因用于MNA潜力评估。PRM也是高度通用的，它分解环状分子（二氧六环，四氢呋喃和环己烷），以及氯化和芳香族污染物，包括氯乙烯，1，2-二氯乙烷，苯和甲苯。这是关于PRM降解除二氧杂环己烷之外的各种短链烷烃和乙烯的能力的第一份报告，揭示了其在利用丙烷、异丁烷或其他气态烷烃/烯烃（例如，乙烷、丁烷和乙烯），以选择和刺激本土微生物，解决二氧六环和氯化化合物的混合污染问题。
Monitored natural attenuation (MNA) and engineered bioremediation have been recognized as effective and cost-efficient in situ treatments to mitigate 1,4-dioxane (dioxane) contamination. Dioxane metabolism can be initiated by two catabolic enzymes, propane monooxygenase (PRM) and tetrahydrofuran monooxygenase (THM), belonging to the group-6 and 5 of soluble di-iron monooxygenase family, respectively. In this study, we comprehensively compared catalytic behaviors of PRM and THM when individually expressed in the heterologous host, Mycobacterium smegmatis mc(2)-155. Kinetic results revealed a half-saturation coefficient (K-m) of 53.0 +/- 13.1 mg/L for PRM, nearly 4 times lower than that of THM (235.8 +/- 61.6 mg/L), suggesting that PRM has a higher affinity to dioxane. Exposure with three common co-contaminants (1,1-dichloroethene, trichloroethene, and 1,1,1-trichloroethane) demonstrated that PRM was also more resistant to their inhibition than THM. Thus, dioxane degraders expressing PRM may be more physiologically and ecologically advantageous than those with THM at impacted sites, where dioxane concentration is relatively low (e.g., 250 to 1000 mu g/L) with co-occurrence of chlorinated solvents (e.g., 0.5 to 8 mg/L), underscoring the need of surveying both PRM and THM-encoding genes for MNA potential assessment. PRM is also highly versatile, which breaks down cyclic molecules (dioxane, tetrahydrofuran, and cyclohexane), as well as chlorinated and aromatic pollutants, including vinyl chloride, 1,2-dichloroethane, benzene, and toluene. This is the first report regarding the ability of PRM to degrade a variety of short-chain alkanes and ethene in addition to dioxane, unraveling its pivotal role in aerobic biostimulation that utilizes propane, isobutane, or other gaseous alkanes/alkenes (e.g., ethane, butane, and ethene) to select and fuel indigenous microorganisms to tackle the commingled contamination of dioxane and chlorinated compounds.