Influence of ionic liquids on enzyme-catalyzed reactions

酶催化反应在开发生物技术过程中的新的替代合成路线方面变得越来越重要。然而，许多酶催化反应的反应平衡通常远在底物一侧，因为转化率受到化学限制。在这种平衡限制反应中，通常增加底物浓度以使产率最大化。然而，由于疏水底物在水性反应介质中的低溶解度，该方法通常不适用或仅部分适用。通过在反应介质中加入离子液体，可以优化平衡限制酶促反应的转化率。在该提案中，离子液体将用作水性反应介质的添加剂，以将反应平衡转移到产物侧。此外，在反应介质中加入离子液体可以显著增加底物的溶解度，从而可以系统地提高酶催化反应的转化率和选择性。此外，离子液体可以影响催化酶的活性。为了研究反应平衡，必须在相应的反应条件（温度、pH、IL-浓度）下确保酶活性。所有三种效应的个别研究已经存在于文献中，但到目前为止，它们只在少数反应中被单独考虑，而不是系统地考虑。本研究将通过对这些现象（反应平衡、底物溶解度、酶活性）的系统热力学研究，更好地了解离子液体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预测。在相应的反应条件下测试酶活性，以验证热力学平衡的实现。为了更好地理解IL对酶活性的影响，将测量IL对所研究反应的热力学稳定性和酶的二级结构的影响。为了获得一般知识，考虑两种不同的酶催化反应，每种反应都具有工业相关性。此外，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。这些离子液体具有不同的碱性、疏水性和摩尔质量，基本上考察了这些性质对反应平衡、底物溶解性和酶活性的影响，这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，将有关于使用离子液体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.