含新型亲核体大环多胺锌(Ⅱ)配合物对水解酶的模拟研究

Hydrolytic Metalloenzyme Activity of Zinc (II) Complex of Macrocyclic Polyamines

本文探讨苯酚功能化的大环多胺配体6-(2’-羟基-3’,5’-二溴)-苄基-1,4,8,11-四氮杂环十四烷(L)锌(II)配合物作为水解酶模拟物催化4-硝基苯酚醋酸酯(NA)水解的动力学.研究表明催化水解速率对NA及配合物浓度皆呈一级反应.水解速率遵循速率方程υ=(k_(cat)[Zn]+k_(OH)[OH^-]+k_0)[NA].其二级反应速率常数k_(cat)在一定范围内随pH值的增加而增加.k_(cat)的最大值(k)和k_(OH)分别为0.12,8.55mol^(-1)L·S^(-1).k_0为NA的溶剂解速率常数,其值为1.122×10^(-5)S^(-1)(298K,I=0.10,0.02mol·L^(-1)tris缓冲溶液).k_(cat)值较以前报道的配合物更大,催化活性更高.显示配位酚羟基可作为一种新型亲核体有效地催化NA的水解.配合物对NA水解的催化作用受酸碱平衡控制.根据实验结果提出了催化反应的机理.

The hydrolytic kinetics of p - nitrophenol acetate (NA) catalysized by zinc (II) complex of 6 - (2' - hydroxyl - 3',5' - dibromo) - benzyl -1,4,8,11- tetraazacyclotetradecane has been studied. It was shown that the catalytic hydrolytic rate was of first - order to both zinc (II) complex and NA concentrations.The second-order rate constant kcat= 0. 12mol-1·L·s-1(298K, I = 0. 10, 0. 02mol·L-1 tris buffer). This is one of the most efficient hydrolytic metalloenzyme model compounds reported up to now. The present results show that coordinated phenolate can serve as a new nucleophile that effectively catalyzes the hydrolysis of NA.