Aromatizing Cyclohexa-1,5-diene-1-carbonyl-Coenzyme A Oxidase
Aromatizing Cyclohexa-1,5-diene-1-carbonyl-Coenzyme A Oxidase
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芳香化环六-1,5-二烯-1-羰基-辅酶 A 氧化酶
DOI：
10.1074/jbc.m802841200
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发表时间：
2008
影响因子：
4.8
通讯作者：
M. Boll
中科院分区：
文献类型：
--
作者：
B. Thiele;Oliver Rieder;N. Jehmlich;M. von Bergen;Michael Müller;M. Boll
苯甲酰辅酶a还原酶（BCRs）是兼性厌氧细菌厌氧芳香代谢的关键酶。对氧高度敏感的酶催化底物的atp依赖性还原脱芳，生成环己-1,5-二烯-1-羰基辅酶a（1,5-二烯基辅酶a）。在厌氧生长的反硝化Thauera aromatica提取物中，我们检测到苯甲酸诱导的，苯甲酰辅酶a形成，1,5-二烯基辅酶a受体氧化还原酶活性。该活性与BCR共纯化，但可通过羟基磷灰石层析分离。在天然凝胶上进行活性染色后，鉴定出亚基分子量为Mr 76,000的单体蛋白。色氨酸消化的质谱分析鉴定了NADH氧化酶/2,4-二烯酰辅酶a还原酶/“老黄”酶的肽。富集酶的紫外可见光谱表明存在黄素和Fe/ s辅助因子，并在添加1,5-二烯酰辅酶a后进行漂白。该酶对作为电子受体的二氧具有高亲和力（Km = 10 μm），因此被称为1,5-二烯酰辅酶a氧化酶（DCO）。二氧还原可能生成的产物是H2O。DCO对1,5-二烯基coa （Km = 27 μm）具有高度特异性。DCO的初始速率在+10 mV时呈能斯特曲线，活性达到一半。我们认为，当细菌在陡峭的氧梯度边缘降解芳香族化合物时，DCO为对氧极其敏感的BCR酶提供了保护。DCO中的氧化还原依赖开关保证了DCO仅在氧化应激时具有活性，并规避了BCR和DCO催化的无效脱芳/重芳化反应。
Benzoyl-CoA reductases (BCRs) are key enzymes of anaerobic aromatic metabolism in facultatively anaerobic bacteria. The highly oxygen-sensitive enzymes catalyze the ATP-dependent reductive dearomatization of the substrate, yielding cyclohexa-1,5-diene-1-carbonyl-CoA (1,5-dienoyl-CoA). In extracts from anaerobically grown denitrifying Thauera aromatica, we detected a benzoate-induced, benzoyl-CoA-forming, 1,5-dienoyl-CoA:acceptor oxidoreductase activity. This activity co-purified with BCR but could be partially separated from it by hydroxyapatite chromatography. After activity staining on native gels, a monomeric protein with a subunit molecular weight of Mr 76,000 was identified. Mass spectrometric analysis of tryptic digests identified peptides from NADH oxidases/2,4-dienoyl-CoA reductases/“old yellow” enzymes. The UV-visible spectrum of the enriched enzyme suggested the presence of flavin and Fe/S-cofactors, and it was bleached upon the addition of 1,5-dienoyl-CoA. The enzyme had a high affinity for dioxygen as electron acceptor (Km = 10 μm) and therefore is referred to as 1,5-dienoyl-CoA oxidase (DCO). The likely product formed from dioxygen reduction was H2O. DCO was highly specific for 1,5-dienoyl-CoA (Km = 27 μm). The initial rate of DCO followed a Nernst curve with half-maximal activity at +10 mV. We propose that DCO provides protection for the extremely oxygen-sensitive BCR enzyme when the bacterium degrades aromatic compounds at the edge of steep oxygen gradients. The redox-dependent switch in DCO guarantees that DCO is only active during oxidative stress and circumvents futile dearomatization/rearomatization reactions catalyzed by BCR and DCO.
老黄酶：环烯酮的芳构化和新型歧化反应的机制。
影响因子：
2.9
作者：
Vaz,AD;Chakraborty,S;Massey,V
通讯作者：
Massey,V
DOI：
--
发表时间：
1993
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Stott,K;Saito,K;Thiele,DJ;Massey,V
通讯作者：
Massey,V