The Identification of DepB: An Enzyme Responsible for the Final Detoxification Step in the Deoxynivalenol Epimerization Pathway in Devosia mutans 17-2-E-8.
The Identification of DepB: An Enzyme Responsible for the Final Detoxification Step in the Deoxynivalenol Epimerization Pathway in Devosia mutans 17-2-E-8.
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DOI：
10.3389/fmicb.2018.01573
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发表时间：
2018
影响因子：
5.2
通讯作者：
Zhou T
中科院分区：
文献类型：
--
作者：
Carere J;Hassan YI;Lepp D;Zhou T
脱氧雪腐镰刀菌烯醇（DON）是谷物中最常见的真菌毒素之一，被DON污染的谷物可导致人类和动物的健康问题，并导致严重的经济损失。目前还没有可行的方法来补救受影响的谷物。随着发现可以将DON转化为相对无毒的立体异构体3-epi-DON的微生物，生物解毒方法的开发变得越来越合理。虽然能够解毒DON的细菌已经知道了一段时间，但直到最近才确定了负责的酶。在Devosia mutans 17-2-E-8（Devosia sp. 17-2-E-8）中，两步DON差向异构化（Dep）途径（称为Dep系统）完成该反应。DepA最近被鉴定为负责将DON转化为3-酮-DON的酶，并且在本报告中，DepB，一种NADPH依赖性脱氢酶，被鉴定为该途径中的第二步和最后一步。DepB容易催化3-酮-DON还原为3-表-DON。DepB显示为中等热稳定的，因为它在55°C下热处理后没有失去显著活性，并且它适合于冻干。DepB在一定范围的pH值（5-9）下起作用，并且在多种常见缓冲液中同样良好地起作用。DepB显然是NADPH依赖性酶，因为它比NADH更有效地利用它。Dep途径中最后一步的发现可能提供一种通过酶解毒系统最终减轻谷物中DON污染损失的方法。该系统的进一步开发将需要关注Dep酶在模拟工业相关条件的条件下的活性，以测试它们在诸如玉米碾磨、燃料乙醇发酵或直接在动物饲料中使用的功能。
Deoxynivalenol (DON) is one of the most common mycotoxins found in cereal grains and grains contaminated with DON can cause health issues for both humans and animals and result in severe economic losses. Currently there is no feasible method to remediate affected grains. The development of a biological method for detoxification is becoming increasingly more plausible with the discovery of microbes which can transform DON to a relatively non-toxic stereoisomer, 3-epi-DON. Although bacteria capable of detoxifying DON have been known for some time, it is only recently an enzyme responsible was identified. In Devosia mutans 17-2-E-8 (Devosia sp. 17-2-E-8) a two-step DON epimerization (Dep) pathway, designated as the Dep system, completes this reaction. DepA was recently identified as the enzyme responsible for the conversion of DON to 3-keto-DON, and in this report, DepB, a NADPH dependent dehydrogenase, is identified as the second and final step in the pathway. DepB readily catalyzes the reduction of 3-keto-DON to 3-epi-DON. DepB is shown to be moderately thermostable as it did not lose significant activity after a heat treatment at 55°C and it is amenable to lyophilization. DepB functions at a range of pH-values (5–9) and functions equally well in multiple common buffers. DepB is clearly a NADPH dependent enzyme as it utilizes it much more efficiently than NADH. The discovery of the final step in the Dep pathway may provide a means to finally mitigate the losses from DON contamination in cereal grains through an enzymatic detoxification system. The further development of this system will need to focus on the activity of the Dep enzymes under conditions mimicking industrially relevant conditions to test their functionality for use in areas such as corn milling, fuel ethanol fermentation or directly in animal feed.