Asymmetric reduction of ketones and β-keto esters by (S)-1-phenylethanol dehydrogenase from denitrifying bacterium Aromatoleum aromaticum
Asymmetric reduction of ketones and β-keto esters by (S)-1-phenylethanol dehydrogenase from denitrifying bacterium Aromatoleum aromaticum
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DOI：
10.1007/s00253-014-6309-z
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发表时间：
2015-06-01
影响因子：
5
通讯作者：
Szaleniec, M.
中科院分区：
文献类型：
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作者：
Dudzik, A.;Snoch, W.;Szaleniec, M.
酶催化的酮和酮酯的对映选择性还原已广泛用于生产纯手性结构单元，这些结构单元是工业规模制备生物活性化合物的有价值的合成子。在多种生物催化剂中，来自各种微生物的脱氢酶/还原酶已被用于从羰基化合物制备光学纯的对映体。 (S)-1-苯乙醇脱氢酶 (PEDH) 存在于反硝化细菌 Aromatoleumaromaticum（菌株 EbN1）中，属于短链脱氢酶/还原酶家族。它在厌氧乙苯矿化过程中催化 (S)-1-苯基乙醇立体定向氧化为苯乙酮，同时也催化逆反应，即苯乙酮依赖 NADH 对映选择性还原为 (S)-1-苯基乙醇。在这项工作中，我们介绍了 PEDH 在 42 种前手性酮和 11 种 β-酮酯的不对称还原中应用，生成对映体纯仲醇。该反应的高对映选择性可以通过对接实验以及理论酶-底物复合物的相互作用和结合能分析来解释，从而产生相应的（S）-或（R）-醇。转化是在间歇式反应器中进行的，使用大肠杆菌细胞，异源产生的 PEDH 作为全细胞催化剂，异丙醇作为反应溶剂和用于 NADH 回收的共底物。酮被转化为相应的仲醇，具有优异的对映体过量和高产率。此外，还研究了九种对位取代的苯乙酮衍生物的产物形成过程，并通过神经网络模型进行了描述，从而可以预测反应器行为并提供对酶反应性的见解。最后，从反应进程曲线得出这些底物转化的平衡常数。获得的值与理论预测非常吻合。
Enzyme-catalyzed enantioselective reductions of ketones and keto esters have become popular for the production of homochiral building blocks which are valuable synthons for the preparation of biologically active compounds at industrial scale. Among many kinds of biocatalysts, dehydrogenases/reductases from various microorganisms have been used to prepare optically pure enantiomers from carbonyl compounds. (S)-1-phenylethanol dehydrogenase (PEDH) was found in the denitrifying bacterium Aromatoleum aromaticum (strain EbN1) and belongs to the short-chain dehydrogenase/reductase family. It catalyzes the stereospecific oxidation of (S)-1-phenylethanol to acetophenone during anaerobic ethylbenzene mineralization, but also the reverse reaction, i.e., NADH-dependent enantioselective reduction of acetophenone to (S)-1-phenylethanol. In this work, we present the application of PEDH for asymmetric reduction of 42 prochiral ketones and 11 beta-keto esters to enantiopure secondary alcohols. The high enantioselectivity of the reaction is explained by docking experiments and analysis of the interaction and binding energies of the theoretical enzyme-substrate complexes leading to the respective (S)- or (R)-alcohols. The conversions were carried out in a batch reactor using Escherichia coli cells with heterologously produced PEDH as whole-cell catalysts and isopropanol as reaction solvent and cosubstrate for NADH recovery. Ketones were converted to the respective secondary alcohols with excellent enantiomeric excesses and high productivities. Moreover, the progress of product formation was studied for nine para-substituted acetophenone derivatives and described by neural network models, which allow to predict reactor behavior and provides insight on enzyme reactivity. Finally, equilibrium constants for conversion of these substrates were derived from the progress curves of the reactions. The obtained values matched very well with theoretical predictions.