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首页> 外文期刊>Chemistry: A European journal >A Catalytic Antibody against a Tocopherol Cyclase Inhibitor
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A Catalytic Antibody against a Tocopherol Cyclase Inhibitor

机译：生育酚环化酶抑制剂的催化抗体

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摘要

The cyclic ammonium cation 5 and its guanidinium analogue 4 are inhibitors of tocopherol cyclase.Monoclonal antibodies were raised against protein conjugates of the haptens 1-3 and screened for catalytic reactions with alkene 8,a short chain analogue of the natural substrate phytyl-hydro-quinone 6,and its enol ether analogues 10 a,b.Antibody 16E7 raised against hapten 3 was found to catalyze the hydrolysis of Z enol ether 10 a to form hemiacetal 12 with an apparent rate acceleration of k_(cat)/k_(uncat)=1400.Antibody 16E7 also catalyzed the elimination of Kemp's benzisoxazole 59.The absence of cyclization in the reaction of enol ether 10 a was attributed to the competition of water molecules for the oxo-carbonium cation intermediate within the antibody binding pocket.Hapten and reaction design features contributing to this outcome are discussed.Antibody 16E7 provides the first example of a carboxyl group acting both as an acid in an intrinsically acid-catalyzed process and as a base in an intrinsically base-catalyzed process,as expected from first principles.In contrast to the many examples of general-acid-catalyzed processes known to be catalyzed by catalytic antibodies,the specific-acid-catalyzed cyclization of phytyl-hy-droquinone 6 or its analogue 8 still eludes antibody catalysis.
机译：环状铵阳离子5及其胍类似物4是生育酚环化酶的抑制剂。针对半抗原1-3的蛋白质结合物产生了单克隆抗体，并筛选了与烯烃8的催化反应的催化剂，烯烃8是天然底物植酸氢的短链类似物醌6及其烯醇醚类似物10a，b。发现针对半抗原3的抗体16E7催化Z烯醇醚10a水解形成半缩醛12，表观速率加速k_（cat）/ k_（uncat） = 1400。抗体16E7也催化消除肯普氏苯并异恶唑59.烯醇醚10a反应中没有环化作用是由于水分子竞争抗体结合口袋中的羰基碳阳离子中间体而引起的。讨论了有助于该结果的设计特征。抗体16E7提供了羧基在固有酸催化过程中既充当酸又充当其碱的第一个例子。与第一原理所期望的一样，是一种固有的碱催化方法。与已知由催化抗体催化的一般酸催化方法的许多例子相反，植酸-氢-醌6或其化合物的特异性酸催化环化类似物8仍未进行抗体催化。

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