A new approach to preparative enzymatic synthesis
A new approach to preparative enzymatic synthesis
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制备酶法合成的新方法
DOI：
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发表时间：
1977
影响因子：
3.8
通讯作者：
I. Berezin
中科院分区：
文献类型：
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作者：
A. Klibanov;G. Samokhin;K. Martínek;I. Berezin
提出了一种在水-有机体系中制备有机合成的新途径。它基于酶促过程在“水-水-不混溶有机溶剂”双相系统中进行的想法。因此，酶定位于水相-这消除了稳定酶以防止非水溶剂失活的传统问题。因此，与常用的组合“水-水-可混溶有机溶剂”相反，在建议的系统中，水的含量可能是无限小的。这使得人们可以极大地改变反应平衡，形成作为反应产物的水（酯和酰胺的合成，氨基酸、糖和核苷酸的聚合，脱水反应等）。系统由两相组成的事实为平衡转移提供了另一个非常重要的来源，即试剂从一相转移到另一相的自由能。推导了两相体系的平衡常数与水相和非水相的体积比以及试剂在两相间的分配系数的关系。实验验证了该方法的有效性，并分别以醇和酸为原料合成了N -乙酰- L -色氨酸乙酯。多孔玻璃用胰凝乳蛋白酶水溶液浸渍，悬浮在含有N -乙酰- L -色氨酸和乙醇的氯仿中。在水中（无有机相），酯的产率约为0.01%，而在双相体系中，酯的产率几乎为100%。这个思想适用于许多制备性酶促反应。
A new approach to preparative organic synthesis in aqueous–organic systems is suggested. It is based on the idea that the enzymatic process is carried out in a biphasic system “water–water‐immiscible organic solvent.” Thereby the enzyme is localized in the aqueous phase—this eliminates the traditional problem of stabilizing the enzyme against inactivation by a nonaqueous solvent. Hence, in contrast to the commonly used combinations “water–water‐miscible organic solvent,” in the suggested system the content of water may be infinitely low. This allows one to dramatically shift the equilibrium of the reactions forming water as a reaction product (synthesis of esters and amides, polymerization of amino acids, sugars and nucleotides, dehydration reactions, etc.) toward the products. The fact that the system consists of two phases provides another very important source for an equilibrium shift, i.e., free energies of the transfer of a reagent from one phase to the other. Equations are derived describing the dependence of the equilibrium constant in a biphasic system on the ratio of the volumes of the aqueous and nonaqueous phases and the partition coefficients of the reagents between the phases. The approach has been experimentally verified with the synthesis of N‐acetyl‐L‐tryptophan ethyl ester from the respective alcohol and acid. Porous glass was impregnated with aqueous buffer solution of chymotrypsin and suspended in chloroform containing N‐acetyl‐L‐tryptophan and ethanol. In water (no organic phase) the yield of the ester is about 0.01%, whereas in this biphasic system it is practically 100%. The idea is applicable to a great number of preparative enzymatic reactions.