人脑及红细胞膜乙酰胆碱酯酶的芳基酰胺酶活性

采用联合亲和层析法从人小脑及红细胞膜中纯化了ＡＣｈＥ，纯化的人脑及红细胞ＡＣｈＥ在ＳＤＳ－ＰＡＧＥ上呈一主带，分子量约为６６０００。人脑ＡＣｈＥ制备酯酶与酰胺酶比活性分别为１２９９与１４３Ｕ／ｍｇ，人红细胞ＡＣｈＥ制备分别为４５８４与７４７Ｕ／ｍｇ。人脑及红细胞ＡＣｈＥ制备的酯酶与酰胺酶活性最适ｐＨ较接近，在ｐＨ７．５－８．０之间，酯酶活性底物ＡＴＣｈ对其芳基酰胺酶活性有抑制作用。ＩＣ_（５０）分别为１０．２×１０~（－３）及３×１０~（－３）ｍｏｌ／Ｌ。梭曼对其酯酶及酰胺酶活性均有明显抑制作用，说明二者均需活性中心丝氨酸参与。

Aryl Acylamidase Activity of Acetylcholinesterases from Human Cerebellum and Erythrocytes

The acetylcholinesterase(AChE)was purified from human cerebellum and erythrocytes by co-affinity chromatography. Both of the AChEs purified from human cerebellum and erythrocytes showed one main band on SDS-PAGE with a molecular weight about 66000 dalton. The specific activities of cholinesterase and aryl acylamidase were 1299 and 143U/mg respectively for human cerebellum AchE, 4584 and 747U/mg respectively for human erythrocyte AChE. The optimal pH of cholinesterase and aryl acylamidase for AChEs from human cerebellum and erythrocytes were close, from 7.5 to 8.0. Acetylthiocholine (ATCh), a substrate of cholinesterase inhibited the aryl acylamidase activity of AChE both from the human cerebellum and erythrocytes. Its IC_50 were 10.2×10￣(-3) and 3×10￣(-3)mol/L respectively.Soman (pinacolylmethylphosphonofeuoridate) showed inhibition for both cholinesterase and aryl acylamidase activities of AChEs from human cerebellum and erythrocytes, which demonstrated that the serine in active center was essential for both types of enzyrme activity.