Influence of ionic liquids on enzyme-catalyzed reactions

在生物技术过程中，酶催化反应对于开发新的替代合成路线变得越来越重要。然而，由于热力学上的限制，许多酶催化反应的反应平衡往往偏向底物一侧。在这种受平衡限制的反应中，为了最大化产率，通常会增加底物浓度。然而，由于疏水底物在水反应介质中的溶解度较低，这种方法往往不适用或只有部分适用。在反应介质中加入离子液体(ILS)可以优化平衡限制性酶反应的转化率。在该方案中，离子液体将被用作水反应介质的添加剂，以使反应平衡向产物侧转移。此外，在反应介质中加入ILS可以显著增加底物的溶解度，从而系统地提高酶催化反应的转化率和选择性。此外，ILS还会影响酶的活性。为了研究反应平衡，必须确保在相应的反应条件下(温度、pH、IL-浓度)酶的活性。文献中已经存在对所有这三种影响的单独研究，然而到目前为止，它们只被单独考虑为少量的反应，并且没有系统地考虑。本研究项目通过对这些现象(反应平衡、底物溶解度、酶活性)的系统热力学研究，有助于更好地理解ILS对酶催化反应的影响。这些性质将通过实验确定；反应平衡和底物溶解度也将通过热力学模型进行预测。在各自的反应条件下测试酶的活性，以验证达到热力学平衡。为了更好地了解IL对酶活性的影响，我们将测量ILS对所研究反应的热力学稳定性和酶的二级结构的影响。为了获得一般性知识，我们考虑了两种不同的酶催化反应，每个反应都具有工业相关性。此外，还研究了四种离子液体对酶催化反应平衡、底物溶解度和酶活性的影响。这些离子液体的碱性/疏水性/摩尔质量不同，为了从根本上研究这些性质对反应平衡、底物溶解度和酶活性的影响，这一研究项目将有助于理解不同化学性质的添加剂对酶催化反应热力学的影响。此外，将有关于使用ILS作为生物反应添加剂的具体定量结果。

Enzyme-catalyzed reactions become more and more important for the development of new alternative synthetic routes in biotechnological processes. However, the reaction equilibrium of many enzyme-catalyzed reactions is often far on the side of the substrates, since the conversion is thermodynamically limited. In such equilibrium-limited reactions, the substrate concentrations are typically increased in order to maximize yields. However, this method is often not or only partially applicable due to low solubility of hydrophobic substrates in aqueous reaction media. The conversion of equilibrium limited enzymatic reactions can be optimized by the presence of ionic liquids (ILs) in the reaction medium. In this proposal ILs will be used as additives to aqueous reaction media in order to shift the reaction equilibrium to the product side. In addition, substrate solubilities can significantly be increased upon addition of ILs in the reaction medium, thus conversion and selectivity of enzyme-catalyzed reactions can be systematically improved. Furthermore, the ILs can affect the catalytic enzyme activity. For investigations of the reaction equilibrium the enzyme activity has to be ensured under the respective reaction conditions (temperature, pH, IL-concentration). Individual studies of all three effects already exist in the literature, however so far they have only been considered separately for a low number of reactions and not systematically. This research project will contribute by a systematic thermodynamic study of these phenomena (reaction equilibrium, substrate solubility, enzyme activity) to a better understanding of the influence of ILs on enzyme-catalyzed reactions. These properties will be determined experimentally; reaction equilibria and substrate solubilities will also be predicted with a thermodynamic model. The enzyme activity is tested for the respective reaction conditions in order to verify the attainment of thermodynamic equilibrium. For a better understanding of the IL-effect on the enzyme activity the effect of ILs on the thermodynamic stability and on the secondary structure of the enzymes of the investigated reactions will be measured.In order to achieve general knowledge, two different enzyme-catalyzed reactions are considered, each having industrial relevance. In addition, four ILs are studied with respect to their influence on the equilibrium of enzyme-catalyzed reactions, substrate solubility and enzyme activity. These ILs differ in basicity / hydrophobicity / molar mass in order to investigate basically the influence of these properties on reaction equilibrium, substrate solubility and enzyme activity.This research project will contribute significantly to the understanding of the influence of additives of different chemical natures on the thermodynamics of enzyme-catalyzed reactions. In addition, there will be specific quantitative results on the use of ILs as additives for biological reactions.