对二异丙基氟磷酸酯不可逆抑制胆碱酯酶的亲和力和磷酸化常数的测定。

Measurement of the affinity and phosphorylation constants governing irreversible inhibition of cholinesterases by di-isopropyl phosphorofluoridate.

Main A R, Iverson F

Biochem J. 1966 Aug;100(2):525-31. doi: 10.1042/bj1000525.

Abstract

A procedure is described for determining the affinity constant K(a) and the phosphorylation constant k(p) for the inhibition by di-isopropyl phosphorofluoridate of erythrocyte acetylcholinesterase and serum cholinesterase. The procedure depends on the use of a specially designed reaction vessel with which incubation times as short as 1.2sec. could be obtained at any convenient temperature. 2. The K(a) of acetylcholinesterase decreased from 1.58 (+/-0.22)x10(-3)m at 5 degrees to 1.17 (+/-0.10)x10(-3)m at 25 degrees and the associated change in enthalpy was 2980 cal. 3. The k(p) of acetylcholinesterase increased from 11.9 (+/-0.7)min.(-1) at 5 degrees to 40.7 (+/-1.4)min.(-1) at 25 degrees , indicating an activational energy of 9600 cal. The change in entropy associated with K(a) was 23.5 cal. degree(-1) at 25 degrees . 4. At 5 degrees , the K(a) and k(p) of serum cholinesterase were 9.95 (+/-1.10)x10(-6)m and 11.2 (+/-0.63)min.(-1) respectively. 5. The 150-fold difference in the inhibitory power of di-isopropyl phosphorofluoridate for the two cholinesterases was attributed entirely to differences in affinity.

摘要

本文描述了一种用于测定二异丙基氟磷酸酯对红细胞乙酰胆碱酯酶和血清胆碱酯酶抑制作用的亲和常数K(a)和磷酸化常数k(p)的方法。该方法依赖于使用一种特殊设计的反应容器，利用它可以在任何适宜温度下获得短至1.2秒的孵育时间。2. 乙酰胆碱酯酶的K(a)在5℃时为1.58（±0.22）×10⁻³m，在25℃时降至1.17（±0.10）×10⁻³m，焓变相关值为2980卡。3. 乙酰胆碱酯酶的k(p)在5℃时为11.9（±0.7）分钟⁻¹，在25℃时增至40.7（±1.4）分钟⁻¹，表明活化能为9600卡。25℃时与K(a)相关的熵变是23.5卡·度⁻¹。4. 在5℃时，血清胆碱酯酶的K(a)和k(p)分别为9.95（±1.10）×10⁻⁶m和11.2（±0.63）分钟⁻¹。5. 二异丙基氟磷酸酯对两种胆碱酯酶抑制能力的150倍差异完全归因于亲和力的差异。