Clapés P, Valencia G, Adlercreutz P
Unit for Peptide Chemistry and Biochemistry, Centro de Investigación y Desarrollo (C.S.I.C.), Barcelona, Spain.
Enzyme Microb Technol. 1992 Jul;14(7):575-80. doi: 10.1016/0141-0229(92)90129-c.
alpha-Chymotrypsin deposited on Celite was used to catalyse peptide synthesis reactions between N-protected amino acid esters and leucine amide in organic media with low water content. The influence of the solvent and the thermodynamic water activity on the reaction kinetics was studied. The substrate specificity in the reactions was shown to be a combination of the substrate specificity of the enzyme in aqueous media and the influence of the solvents. The magnitude of the solvent effects differed greatly depending on the substrates used. In hydrophobic solvents high reaction rates were observed and the competing hydrolysis of the ester substrate occurred to only a minor extent. Reactions occurred at water activities as low as 0.11, but the rate constants increased with increasing water activity and were about two orders of magnitude higher at the highest water activity tested (0.97).
沉积在硅藻土上的α-胰凝乳蛋白酶用于催化低含水量有机介质中N-保护氨基酸酯与亮氨酸酰胺之间的肽合成反应。研究了溶剂和热力学水活度对反应动力学的影响。结果表明，反应中的底物特异性是酶在水性介质中的底物特异性与溶剂影响的结合。溶剂效应的大小因所用底物的不同而有很大差异。在疏水溶剂中观察到高反应速率，酯底物的竞争性水解仅在很小程度上发生。反应在低至0.11的水活度下发生，但速率常数随水活度的增加而增加，在测试的最高水活度（0.97）下约高两个数量级。
