Department of Physical and Chemical Sciences , University of L'Aquila , Via Vetoio , Coppito, 67100 L'Aquila , Italy.
CEMIN, Centre of Excellence on Nanostructured Innovative Materials, Department of Chemistry, Biology and Biotechnology , University of Perugia , Via Elce di Sotto 8 , 06123 Perugia , Italy.
Langmuir. 2018 Sep 25;34(38):11510-11517. doi: 10.1021/acs.langmuir.8b02255. Epub 2018 Sep 11.
In this work, we present the effects of ionic and zwitterionic surfactants on the hydrolytic activity of Candida rugosa lipase (CRL), one of the most important and widely used microbial lipases. A series of amine N-oxide surfactants was studied to explore the relationship between their molecular structures and their effect on catalytic properties of CRL. These zwitterionic amphiphiles are known for their ability to form aggregates that can increase their size, thanks to a sphere-rod transition, without any additive. Enzyme activity seemed to be improved by morphological changes of micelles from spherical to rod-like, and the structure of the monomers played a crucial role in this transition. In fact, all the amine oxides investigated provoked superactivation, but the CRL activity increased by lengthening the alkyl chain of N-oxide surfactants, whereas it decreased in the presence of bulky head groups. Superactivity was mainly because of an increase in k (0.57 s in buffer, 0.80-1.99 s in surfactant solutions) and, in some cases, a decrease in K (2 × 10 M in buffer, 1.08-4.28 × 10 M in surfactant solutions). Micelles seemed to play a dual role: superactivity occurred at surfactant concentrations higher than their critical micelle concentration, but, on the other hand, micelles subtracted the substrate from the bulk, making it unavailable for the catalysis.
在这项工作中，我们研究了离子型和两性离子型表面活性剂对最常用的微生物脂肪酶之一——假丝酵母脂肪酶（CRL）的水解活性的影响。我们研究了一系列胺 N-氧化物表面活性剂，以探索它们的分子结构与其对 CRL 催化性能的关系。这些两性离子两亲物以其形成聚集体的能力而闻名，由于球体-棒状转变，其大小可以增加，而无需任何添加剂。酶活性似乎通过胶束从球形到棒状的形态变化得到改善，而单体的结构在这种转变中起着关键作用。事实上，所有研究的氧化胺都引起了超活性，但 CRL 活性随着 N-氧化物表面活性剂的烷基链的延长而增加，而在存在大体积头基时则降低。超活性主要是由于 k（缓冲液中为 0.57 s，表面活性剂溶液中为 0.80-1.99 s）增加，在某些情况下 K 减小（缓冲液中为 2×10 M，表面活性剂溶液中为 1.08-4.28×10 M）。胶束似乎发挥了双重作用：在表面活性剂浓度高于其临界胶束浓度时发生超活性，但另一方面，胶束从本体中除去了底物，使其无法进行催化。
