Effects of Choline, Acetate and Citrate on the Activity of the Choline Acetylating System of Mammalian Brain

Abstract

Nachmansohn, Hestrin and Voripaieff¹ have reported that a highly active preparation, capable of synthesizing acetylcholine from acetate and choline (with certain other additions), can be obtained from extracts of acetone-dried brain (rabbit) by fractional precipitation with ammonium sulphate. The active material is contained in the 16–36 per cent fraction (16–36 gm. to 100 c.c. volume ammonium sulphate) and requires calcium ions to be fully effective. Two means of identifying acetylcholine are used: (1) assay on the frog rectus abdominis muscle and (2) chemical determination by the method of Hestrin². The aforementioned authors find, however, that bioassay may give values more than twice those obtained chemically, and that incubation without choline yields bio-active material (equivalent to 80–100 µgm. acetylcholine/ml. of incubate) which is not chemically identifiable as acetylcholine. The nature of the substance responsible is unknown. It is formed largely by the 25–36 per cent ammonium sulphate fraction ; and acetylcholine by the 16–25 per cent fraction.