Cometabolic degradation plays a prominent role in bioremediation of commingled groundwater contamination (e.g., chlorinated solvents and the solvent stabilizer 1,4-dioxane [dioxane]). In this study, we untangled the diversity and catalytic functions of multicomponent monooxygenases in Azoarcus sp. strain DD4, a Gram-negative propanotroph that is effective in degrading dioxane and 1,1-dichloroethylene (1,1-DCE). Using a combination of knockout mutagenesis and heterologous expression, a toluene monooxygenase (MO) encoded by the tmoABCDEF gene cluster was unequivocally proved to be the key enzyme responsible for the cometabolism of both dioxane and 1,1-DCE. Interestingly, in addition to utilizing toluene as a primary substrate, this toluene MO can also oxidize propane into 1-propanol. Expression of this toluene MO in DD4 appears inducible by both substrates (toluene and propane) and their primary hydroxylation products (m-cresol, p-cresol, and 1-propanol). These findings coherently explain why DD4 can grow on propane and express toluene MO for active cooxidation of dioxane and 1,1-DCE. Furthermore, upregulation of tmo transcription by 1-propanol underlines the implication potential of using 1-propanol as an alternative auxiliary substrate for DD4 bioaugmentation. The discovery of this toluene MO in DD4 and its degradation and induction versatility can lead to broad applications, spanning from environmental remediation and water treatment to biocatalysis in green chemistry.

中文翻译：

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发现了一种可氧化的丙烷单加氧菌中的1,4-二恶烷和1,1-二氯乙烯共氧化的甲苯单加氧酶。菌株DD4。

合成代谢降解在混合地下水污染的生物修复中起着重要作用（例如，氯化溶剂和溶剂稳定剂1,4-二恶烷[dioxane]）。在这项研究中，我们理清了固氮菌中多组分单加氧酶的多样性和催化功能。菌株DD4，是革兰氏阴性菌，对降解二恶烷和1,1-二氯乙烯（1,1-DCE）有效。结合使用敲除诱变和异源表达，由tmoABCDEF编码的甲苯单加氧酶（MO）毫无疑问，基因簇是导致二恶烷和1,1-DCE发生新陈代谢的关键酶。有趣的是，除了利用甲苯作为主要底物，该甲苯MO还可以将丙烷氧化成1-丙醇。底物（甲苯和丙烷）及其伯羟基化产物（间甲酚，对甲酚和1-丙醇）均可诱导该甲苯MO在DD4中的表达。这些发现一致地解释了为什么DD4可以在丙烷上生长并表达甲苯MO，以实现二恶烷和1,1-DCE的活性共氧化。此外，tmo的上调1-丙醇的转录突显了使用1-丙醇作为DD4生物强化的替代辅助底物的潜在潜力。DD4中这种甲苯MO的发现及其降解和诱导多功能性可以导致广泛的应用，从环境修复和水处理到绿色化学中的生物催化。