Bru R, Sánchez-Ferrer A, Garcia-Carmona F
Departmento de Bioquímica y Biología Molecular, Facultad de Biología, Universidad de Murcia, Spain.
Biochem J. 1989 Apr 15;259(2):355-61. doi: 10.1042/bj2590355.
The present work deals with a theoretical model of catalysis by enzymes entrapped in reverse micelles. Three aspects of the enzyme-reverse-micelle system have been considered: structure, dynamics and enzyme distribution and catalysis in reverse micelles. A proposed structural model of reverse micelles [El Seoud (1984) in Reverse Micelles (Luisi, P. L. & Straub, B. E., eds.), p. 81, Plenum Press, New York] consists of three domains: surfactant apolar tails, bound water and free water. Dynamics are based on a dynamic equilibrium of association-dissociation that lead one to consider the dispersed polar phase as a pseudo-continuous phase [Luisi, Giomini, Pileni & Robinson (1988) Biochim. Biophys. Acta 947, 207-246]. Enzyme is distributed among the reverse-micelle domains and it expresses a catalytic constant for each one of them. The overall activity is calculated taking into account the volume in which enzyme is solubilized, and expressed as a function of the whole volume (V). The characteristic parameters of reverse micelles, omega 0 (= [H2O]/[surfactant]) and theta (= % water, v/v), were investigated as modulators of enzymic activity. Three basic patterns of modulation by omega 0 were found depending on which domain the enzyme expressed the highest catalytic constant. Combinations of those basic patterns lead to other modulation types that can be found experimentally, such as superactivation. Other combinations predict behaviour patterns not described to date, such as superinhibition. Dependence of catalytic activity on theta was only stated at omega 0 values around a critical value, which coincides with the appearance of free water.
本研究涉及包裹于反胶束中的酶催化作用的理论模型。我们考虑了酶 - 反胶束系统的三个方面：结构、动力学以及反胶束中酶的分布与催化作用。一种提出的反胶束结构模型[埃尔·塞乌德（1984年），载于《反胶束》（路易西，P. L. 与施特劳布，B. E. 编），第81页，普伦出版社，纽约]由三个区域组成：表面活性剂的非极性尾部、结合水和自由水。动力学基于缔合 - 解离的动态平衡，这使得人们将分散的极性相视为准连续相[路易西、乔米尼、皮莱尼与罗宾逊（1988年），《生物化学与生物物理学报》947，207 - 246]。酶分布于反胶束的各个区域，并且在每个区域都表现出一个催化常数。总体活性是在考虑酶溶解的体积的情况下计算得出的，并表示为总体积（V）的函数。研究了反胶束的特征参数ω0（= [H₂O]/[表面活性剂]）和θ（= 水的体积百分比，v/v）作为酶活性调节剂的作用。根据酶在哪个区域表现出最高催化常数，发现了ω0调节的三种基本模式。这些基本模式的组合导致了其他可通过实验发现的调节类型，如超活化。其他组合预测了迄今未描述的行为模式，如超抑制。催化活性对θ的依赖性仅在ω0值接近临界值时才被提及，该临界值与自由水的出现相吻合。
