A cluster of bacterial genes for anaerobic benzene ring biodegradation
A cluster of bacterial genes for anaerobic benzene ring biodegradation
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DOI：
10.1073/pnas.94.12.6484
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发表时间：
1997-06-10
影响因子：
11.1
通讯作者：
Harwood, CS
中科院分区：
文献类型：
--
作者：
Egland, PG;Pelletier, DA;Harwood, CS
还原苯甲酸途径是芳香族污染物和木质素单体厌氧生物降解的中心管道。苯环还原需要一个，这种代谢能力，到目前为止，只在细菌中报道，为了确定这一环境重要的过程的分子基础，我们克隆和分析所需的基因厌氧降解苯甲酸盐和相关化合物的光养细菌，沼泽红球藻。鉴定了24个基因的簇，其包括可能参与厌氧苯甲酸盐降解的12个基因和将相关化合物4-羟基苯甲酸盐和环己烷羧酸盐转化为苯甲酰-CoA的另外的基因。苯甲酰辅酶A还原酶是一种能够克服芳香环共振稳定性的新型酶，其编码基因通过定向诱变进行鉴定。通过测定大肠杆菌中表达的蛋白质的酶活性，鉴定了编码开环酶2-酮基环己烷羧基-CoA水解酶的基因。生理数据和DNA序列分析表明，苯甲酸途径由不寻常的酶环还原和裂解插入酶之间的同源催化脂肪酸降解。克隆的基因应该是有用的探针，以确定苯甲酸盐降解基因从其他代谢不同组的厌氧细菌，如厌氧细菌和硫酸盐还原菌。
A reductive benzoate pathway is the central conduit for the anaerobic biodegradation of aromatic pollutants and lignin monomers. Benzene ring reduction requires a and this metabolic capability has, so far, been reported only in bacteria, To determine the molecular basis for this environmentally important process, we cloned and analyzed genes required for the anaerobic degradation of benzoate and related compounds from the phototrophic bacterium, Rhodopseudomonas palustris. A cluster of 24 genes was identified that includes twelve genes likely to be involved in anaerobic benzoate degradation and additional genes that convert the related compounds 4-hydroxybenzoate and cyclohexanecarboxylate to benzoyl-CoA. Genes encoding benzoyl-CoA reductase, a novel enzyme able to overcome the resonance stability of the aromatic ring, were identified by directed mutagenesis. The gene encoding the ring-cleavage enzyme, 2-ketocyclohexanecarboxyl-CoA hydrolase, was identified by assaying the enzymatic activity of the protein expressed in Escherichia coli. Physiological data and DNA sequence analyses indicate that the benzoate pathway consists of unusual enzymes for ring reduction and cleavage interposed among enzymes homologous to those catalyzing fatty acid degradation. The cloned genes should be useful as probes to identify benzoate degradation genes from other metabolically distinct groups of anaerobic bacteria, such as denitrifying bacteria and sulfate-reducing bacteria.