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首页> 外文期刊>Chemistry: A European journal >Cationic reverse micelles create water with super hydrogen-bond-donor capacity for enzymatic catalysis: Hydrolysis of 2-naphthyl acetate by α-Chymotrypsin
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Cationic reverse micelles create water with super hydrogen-bond-donor capacity for enzymatic catalysis: Hydrolysis of 2-naphthyl acetate by α-Chymotrypsin

机译：阳离子反胶束产生具有超氢键给体容量的水以进行酶催化：α-胰凝乳蛋白酶水解乙酸2-萘酯

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摘要

Reverse micelles (RMs) are very good nanoreactors because they can create a unique microenvironment for carrying out a variety of chemical and biochemical reactions. The aim of the present work is to determine the influence of different RM interfaces on the hydrolysis of 2-naphthyl acetate (2NA) by α-chymotrypsin (α-CT). The reaction was studied in water/benzyl-nhexadecyldimethylammonium chloride (BHDC)/benzene RMs and, its efficiency compared with that observed in pure water and in sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) RMs. Thus, the hydrolysis rates of 2-NA catalyzed by α-CT were determined by spectroscopic measurements. In addition, the method used allows the joint evaluation of the substrate partition constant K_p between the organic and the micellar pseudophase and the kinetic parameters: catalytic rate constant k_(cat), and the Michaelis constant KM of the enzymatic reaction. The effect of the surfactant concentration on the kinetics parameters was determined at constant W _0= [H_2O]/[surfactant], and the variation of W_0 with surfactant constant concentration was investigated. The results show that the classical Michaelis-Menten mechanism is valid for α-CT in all of the RMs systerns studied and that the reaction takes place at both RM interfaces. Moreover, the catalytic efficiency values k_(cat)/K_M obtained in the RMs systems are higher than that reported in water. Furthermore, there is a remarkable increase in α-CT efficiency in the cationic RMs in comparison with the anionic system, presumably due to the unique water properties found in these confined media. The results show that in cationic RMs the hydrogen-bond donor capacity of water is enhanced due to its interaction with the cationic interface. Hence, entrapped water can be converted into "super-water" for the enzymatic reaction studied in this work.
机译：反向胶束（RM）是非常好的纳米反应器，因为它们可以创造独特的微环境，以进行各种化学和生化反应。本工作的目的是确定不同的RM界面对α-胰凝乳蛋白酶（α-CT）水解乙酸2-萘酯（2NA）的影响。在水/苄基-十六烷基二甲基氯化铵（BHDC）/苯RMs中研究了该反应，并与在纯水和1,4-双-2-乙基己基磺基琥珀酸钠（AOT）RMs中观察到的效率进行了比较。因此，通过光谱测量确定了α-CT催化的2-NA的水解速率。此外，所使用的方法可以联合评估有机相和胶束假相之间的底物分配常数K_p以及动力学参数：催化速率常数k_（cat）和酶反应的米氏常数KM。在常数W _0 = [H_2O] / [表面活性剂]的条件下，确定了表面活性剂浓度对动力学参数的影响，并研究了表面活性剂恒定浓度下W_0的变化。结果表明，经典的Michaelis-Menten机制在所有研究的RMs系统中都适用于α-CT，并且反应在两个RM界面均发生。而且，在RMs系统中获得的催化效率值k_（cat）/ K_M高于在水中报道的催化效率值。此外，与阴离子体系相比，阳离子RM中α-CT效率显着提高，这可能是由于在这些受限介质中发现了独特的水性质。结果表明，在阳离子RMs中，水的氢键供体容量由于与阳离子界面的相互作用而增强。因此，对于这项工作中研究的酶促反应，截留的水可以转化为“超级水”。

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