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酶反应区别于一般化学反应的显著特点之一是反应的高活性.为了解释高活性的起因,Koshland等引用内酯化反应的例子提出了“轨道取向(Orbital steering)假说”,这一假说后来引起了争议.Ferreira试图用轨道对称守恒原理说明这种作用,但他并没有考虑到酶催化过程中酶分子上的活性中心与底物的关键部位的具体的分子结构与轨道的性质.永田亲义等曾对二甲胺基乙酸乙酯与胆碱酯酶的反应体系(图1)作过简单讨论,他们是用简单的HMO法,将此体系作为完全的共轭体系来处理,而且只粗略地求出体系的非定域能,没有考察轨道取向作用.在本文中,我们采用半经验分子轨道法(CNDO/2)计算和讨论了这一体系,以期了解酶反应中的轨道相互作用的实质.
One of the salient features of enzymatic reactions that distinguish them from normal chemical reactions is the high activity of the reaction.In order to explain the origin of high activity, Koshland et al., Cited the example of lactonization, which proposed the “Orbital steering hypothesis” Controversial.Ferreira tried to explain this role by the principle of orbital symmetry conservation, but he did not consider the specific molecular structure and orbital properties of the active site on the enzyme molecule and the substrate during enzyme catalysis. Yoshiki et al. Have briefly discussed the reaction of dimethylaminoethyl acetate with cholinesterase (Figure 1). They used a simple HMO method to treat this system as a complete conjugate system and only In this paper, we use the semi-empirical molecular orbital method (CNDO / 2) to calculate and discuss this system in order to understand the orbital interactions in the enzyme reaction The essence.