Anaerobic Degradation of p-Ethylphenol by “Aromatoleum aromaticum” Strain EbN1: Pathway, Regulation, and Involved Proteins
Anaerobic Degradation of p-Ethylphenol by “Aromatoleum aromaticum” Strain EbN1: Pathway, Regulation, and Involved Proteins
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DOI：
10.1128/jb.00409-08
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发表时间：
2008-06
影响因子：
3.2
通讯作者：
Lars Wöhlbrand;H. Wilkes;T. Halder;R. Rabus
中科院分区：
文献类型：
--
作者：
Lars Wöhlbrand;H. Wilkes;T. Halder;R. Rabus
摘要发酵“Aromatophylaromaticum”菌株EbN 1被证明在缺氧条件下利用对乙基苯酚，并被建议采用一种降解途径，这让人想起在相同的细菌中已知的厌氧降解：对乙基苯酚的初始羟基化为1-（4-羟基苯基）-乙醇，然后脱氢为对羟基苯乙酮。可能，随后的羧化和硫解裂解产生对羟基苯甲酰基辅酶A（CoA），其被引导到中心苯甲酰基辅酶A途径中。通过气相色谱-质谱分析和应用氘代对乙基苯酚证实了四个拟议中间体中的三个的底物特异性形成。被认为参与该降解途径的蛋白质以单个大操纵子样结构（约15 kb）编码。其中包括对甲酚甲基羟化酶样蛋白（PchCF），两种预测的醇脱氢酶（ChnA和EbA 309），生物素依赖性羧化酶（XccABC）和硫解酶（TioL）。蛋白质组学分析（二维差异凝胶电泳）揭示了它们在适应对乙基苯酚和对羟基苯乙酮厌氧生长的细胞中的特异性和协调性上调（例如，PchF高达29倍）。目前未知功能的共调节蛋白（例如，EbA 329）可能参与对乙基苯酚和对羟基苯乙酮特异性的溶剂胁迫反应，并与EbN 1菌株的其他芳香族溶剂诱导蛋白相关。
ABSTRACT The denitrifying “Aromatoleum aromaticum” strain EbN1 was demonstrated to utilize p-ethylphenol under anoxic conditions and was suggested to employ a degradation pathway which is reminiscent of known anaerobic ethylbenzene degradation in the same bacterium: initial hydroxylation of p-ethylphenol to 1-(4-hydroxyphenyl)-ethanol followed by dehydrogenation to p-hydroxyacetophenone. Possibly, subsequent carboxylation and thiolytic cleavage yield p-hydroxybenzoyl-coenzyme A (CoA), which is channeled into the central benzoyl-CoA pathway. Substrate-specific formation of three of the four proposed intermediates was confirmed by gas chromatographic-mass spectrometric analysis and also by applying deuterated p-ethylphenol. Proteins suggested to be involved in this degradation pathway are encoded in a single large operon-like structure (∼15 kb). Among them are a p-cresol methylhydroxylase-like protein (PchCF), two predicted alcohol dehydrogenases (ChnA and EbA309), a biotin-dependent carboxylase (XccABC), and a thiolase (TioL). Proteomic analysis (two-dimensional difference gel electrophoresis) revealed their specific and coordinated upregulation in cells adapted to anaerobic growth with p-ethylphenol and p-hydroxyacetophenone (e.g., PchF up to 29-fold). Coregulated proteins of currently unknown function (e.g., EbA329) are possibly involved in p-ethylphenol- and p-hydroxyacetophenone-specific solvent stress responses and related to other aromatic solvent-induced proteins of strain EbN1.