Abstract

The study of many membrane enzymes in an aqueous medium is difficult due to the loss of their catalytic activity, which makes it necessary to use membrane-like systems, such as reverse micelles of surfactants in nonpolar organic solvents. However, it should be taken into account that the micelles are a simplified model of natural membranes, since membranes contain many different components, a significant part of which are phospholipids. In this work, we studied impact of the main phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), on activity of the membrane enzymes using galactonolactone oxidase from Trypanosoma cruzi (TcGAL) and L-galactono-1,4-lactone dehydrogenase from Arabidopsis thaliana (AtGALDH) as examples. Effect of the structure (and charge) of the micelle-forming surfactant itself on the activity of both enzymes has been studied using an anionic surfactant (AOT), a neutral surfactant (Brij-96), and a mixture of cationic and anionic surfactants (CTAB and AOT) as examples. The pronounced effect of addition of PC and PE lipids on the activity of AtGALDH and TcGAL has been detected, which manifests as increase in catalytic activity and significant change in the activity profile. This can be explained by formation of the tetrameric form of enzymes and/or protein–lipid complexes. By varying composition and structure of the micelle-forming surfactants (AOT, CTAB, and Brij-96) it has been possible to change catalytic properties of the enzyme due to effect of the surfactant on the micelle size, lipid mobility, charge, and rigidity of the matrix itself.

中文翻译：

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反胶束系统中脂质基质组成对克氏锥虫半乳糖内酯氧化酶和拟南芥L-半乳糖-1,4-内酯脱氢酶活性的影响

摘要

由于催化活性的丧失，许多膜酶在水介质中的研究很困难，这使得有必要使用膜状系统，例如非极性有机溶剂中表面活性剂的反胶束。然而，应该考虑到胶束是天然膜的简化模型，因为膜含有许多不同的成分，其中很大一部分是磷脂。在这项工作中，我们使用来自克氏锥虫的半乳糖内酯氧化酶 (TcGAL) 和来自拟南芥的 L-半乳糖-1,4-内酯脱氢酶研究了主要磷脂、磷脂酰胆碱 (PC) 和磷脂酰乙醇胺 (PE) 对膜酶活性的影响拟南芥（AtGALDH）为例。使用阴离子表面活性剂 (AOT)、中性表面活性剂 (Brij-96) 以及阳离子和阴离子表面活性剂的混合物研究了形成胶束的表面活性剂本身的结构（和电荷）对两种酶活性的影响（ CTAB 和 AOT）为例。已检测到添加 PC 和 PE 脂质对 AtGALDH 和 TcGAL 活性的显着影响，表现为催化活性增加和活性谱显着变化。这可以通过酶和/或蛋白质-脂质复合物四聚体形式的形成来解释。通过改变形成胶束的表面活性剂（AOT、CTAB 和 Brij-96）的组成和结构，由于表面活性剂对胶束尺寸、脂质迁移率、电荷和刚性的影响，可以改变酶的催化特性矩阵本身。