硅藻土吸附增强的(RS)-2,4-DP对映体选择性酶促水解

利用手性气相色谱技术研究了硅藻土吸附作用对(RS) 2 ,4 二氯苯氧丙酸甲酯(2 ,4 DP)酶促水解对映体选择性的影响。实验结果表明,硅藻土吸附作用显著增强了酶促反应的对映体选择性(ER值由1.5 8增加到5 .31)。进一步研究表明,硅藻土对脂肪酶的吸附,引起酶构象变化,影响农药底物与酶结合的微环境,是酶促反应的对映体选择性增强的主要原因。吸附在硅藻土上的脂肪酶,与R 2 ,4 DP结合更为困难,反应速率下降;而S 2 ,4 DP接近酶反应中心更加容易,反应速率上升。此外,硅藻土吸附作用对农药底物的束缚引起处于“自由状态”的底物减少,也使酶促反应的对映体选择性略有增强

ENHANCED ENANTIOSELECTIVE ENZYMATIC HYDROLYSIS OF(RS)-2,4-DP INDUCED BY ADSORPTION ON KIESELGUHR

Effect of kieselguhr on enantioselectivity of enzymatic hydrolysis of chiral dichlorprop methyl ester (2,4 DP) has been specifically studied by chiral gas chromatography. The results show that the adsorption of lipase on kieselguhr greatly enhanced enantioselectivity of hydrolysis of 2,4 DP with ER increasing from 1.58 to 5.31. It triggered changes in conformation of the enzyme, thus affecting the microenvironment of active sites, which may be the major reason of enhanced enantioselectivity of enzymatic reaction. Due to adsorption on kieselguhr, lipase became harder to combine with R 2,4 DP and the reaction rate of hydrolysis decreased. On the other hand, it was easier for S 2,4 DP to get close to the active sites of lipase, so the rate increased. In addition, adsorption of the pesticide on kieselguhr decreased "free pesticides", which also enhanced the enantioselectivity of hydrolysis of 2,4 DP.