Abstract
In order to determine whether Acetylcholine (ACh) receptor is identical with Cholinesterase (ChE) or not at the pharmacological or functional level, the mechanism of affinity for the active site on ACh receptor surface is considered with the pharmacological and biochemical method using a usefull tool, organophosphoryl choline. These experiments gave following results : 1) By Magnus method using the rectus abdominis of frog, dose-inhibition curve of amyltrimethylammonium salt (ATMA) and dose-inhibition curve of hydrogen ion against it were observed. From the results, one molecule of ATMA combines with an ACh receptor in the process of the contractile response like the case of ACh, and the site of action of hydrogen ion located on the anionic site of ACh receptor. 2) The apparent pKa value of the anionic site of ACh receptor is about 5.92 and very close to that of ChE.3) The two combination constants of organphosphorylcholine with the esteratic site of ACh receptor and of ChE were about 5.53×10-4 and 4.63∼8.27×10-3. Therefore, there is the difference between ACh receptor and ChE regarding the esteratic site. 4) From the correlation between anti-ACh and anti-ChE activity of some organophosphorylcholine derivatives, it was indicated that the former increased in the order of -O-■=O, -O-■=S, and -S-■=S, while the latter was the reverse order of them. 5) From the results above mentioned, it may be concluded that ACh receptor is different from ChE molecule.
