Nitroaromatic compounds are essential materials for chemical industry, but they are also potentially toxic environmental pollutants. Therefore, their sensitive detection and degradation are important concerns. The microbial degradation pathways of nitroaromatic compounds have been studied in detail, but their usefulness needs to be evaluated to understand their potential applications in bioremediation. Here, we developed a rapid and relatively sensitive assay system to evaluate the activities and substrate specificities of nitroaromatic dioxygenases involved in the oxidative biodegradation of nitroaromatic compounds. In this system, nitrous acid, which was released from the nitroaromatic compounds by the dioxygenases, was detected and quantified using the Saltzman reagent. Escherichia coli producing the 3-nitrobenzoic acid dioxygenase complex MnbAB from Comamonas sp. JS46 clearly showed the apparent substrate specificity of MnbAB as follows. MnbAB accepted not only 3-nitrobenzoic acid but also several other p- and m-nitrobenzoic acid derivatives as substrates, although it much preferred 3-nitrobenzoic acid to others. Furthermore, the presence of a hydroxy or an amino group at the ortho position of the nitro group decreased the activity of MnbAB. In addition, MnbAB accepted 2-(4-nitrophenyl)acetic acid as a substrate, which has one additional methylene group between the aromatic ring and the carboxy group of 3-nitrobenzoic acid. This is the first report about the detailed substrate specificity of MnbAB. Our system can be used for other nitroaromatic dioxygenases and contribute to their characterization.

中文翻译：

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使用 Saltzman 试剂通过比色检测快速评估 3-硝基苯甲酸双加氧酶 MnbAB 的底物特异性

硝基芳香族化合物是化学工业必不可少的材料，但它们也是潜在的有毒环境污染物。因此，它们的灵敏检测和降解是重要的问题。硝基芳香族化合物的微生物降解途径已被详细研究，但需要对其有用性进行评估，以了解其在生物修复中的潜在应用。在这里，我们开发了一种快速且相对灵敏的测定系统，用于评估硝基芳香族化合物氧化生物降解中涉及的硝基芳香族双加氧酶的活性和底物特异性。在该系统中，通过双加氧酶从硝基芳香族化合物中释放出的亚硝酸，使用 Saltzman 试剂进行检测和定量。大肠杆菌产生来自 Comamonas sp. 的 3-硝基苯甲酸双加氧酶复合物 MnbAB。JS46 清楚地显示了 MnbAB 的明显底物特异性，如下所示。MnbAB 不仅接受 3-硝基苯甲酸，还接受其他几种对硝基苯甲酸和间硝基苯甲酸衍生物作为底物，尽管它比其他人更喜欢 3-硝基苯甲酸。此外，在硝基的邻位存在羟基或氨基会降低 MnbAB 的活性。此外，MnbAB 接受 2-(4-硝基苯基)乙酸作为底物，它的芳环和 3-硝基苯甲酸的羧基之间有一个额外的亚甲基。这是关于 MnbAB 的详细底物特异性的第一份报告。我们的系统可用于其他硝基芳族双加氧酶并有助于其表征。