Traverso R, Moretto A, Lotti M
Universita' degli Studi di Padova, Istituto di Medicina del Lavoro, Italy.
Biochem Pharmacol. 1989 Feb 15;38(4):671-6. doi: 10.1016/0006-2952(89)90214-1.
Some characteristics of the hydrolysis of O,O-dimethyl-2,2 dichlorovinyl phosphate (DDVP) by human serum are reported and compared with the hydrolysis of O,O-diethyl-4-nitrophenyl phosphate (paraoxon) which is a substrate for Paraoxonase, a known "A"-esterase of human serum. When incubated with human serum, DDVP was losing its inhibitory power toward acetylcholinesterase (AChE). The loss of DDVP followed first order kinetics and was proportional to serum dilution. The disappearance of DDVP after incubation with human serum was not due to protein binding. Apparent Km and Vm for the hydrolysis of DDVP were 7.1 mM and 143 nmol.min-1.ml-1. The pH sensitivity, EDTA inhibitory and Ca2+ requirements of DDVP-ase were similar to those of Paraoxonase. DDVP inhibited the Paraoxonase activity and paraoxon inhibited the DDVP-ase activity. Ca2+, Ag+ and Hg2+ were better inhibitors of the Paraoxonase than the DDVP-ase. The rate of heat inactivation was also different; at 55 degrees Paraoxonase inactivated almost completely within 10 min, while DDVP-ase lost only about 10% activity over 1 hr. Consequently, DDVP-ase and Paraoxonase can be differentiated by means of heat sensitivity. The DDVP-ase was normally distributed in a population of 60 individuals, while Paraoxonase is known to show a marked polymorphism.
本文报道了人血清对O,O-二甲基-2,2-二氯乙烯基磷酸酯（敌敌畏）的水解特性，并与O,O-二乙基-4-硝基苯基磷酸酯（对氧磷）的水解情况进行了比较，对氧磷是血清中已知“A”酯酶——对氧磷酶的底物。与人血清一起温育时，敌敌畏对乙酰胆碱酯酶（AChE）的抑制能力逐渐丧失。敌敌畏的丧失遵循一级动力学，且与血清稀释度成正比。敌敌畏与人血清温育后的消失并非由于蛋白质结合。敌敌畏水解的表观Km和Vm分别为7.1 mM和143 nmol·min-1·ml-1。敌敌畏酶的pH敏感性、EDTA抑制作用和Ca2+需求与对氧磷酶相似。敌敌畏抑制对氧磷酶活性，对氧磷抑制敌敌畏酶活性。Ca2+、Ag+和Hg2+对对氧磷酶的抑制作用比对敌敌畏酶更强。热失活速率也不同；在55℃时，对氧磷酶在10分钟内几乎完全失活，而敌敌畏酶在1小时内仅丧失约10%的活性。因此，可通过热敏感性区分敌敌畏酶和对氧磷酶。敌敌畏酶在60名个体中呈正态分布，而对氧磷酶已知表现出明显的多态性。
