Anticholinesterase action of a bromine compound isolated from human cerebrospinal fluid.

L-1- Methylheptyl -gamma- bromoacetoacetate was found to be a competitive inhibitor of the acetylcholinesterases (electric eel, Ki = 17.2 microM; rat brain, Ki = 32.6 microM) and of butyrylcholinesterase (horse serum, Ki = 1.2 microM). The L-isomer was a more effective inhibitor than the D-isomer. The bromine atom at the gamma-position of the acidic moiety, the specific length of the carbon chain constituting the secondary alcohol moiety, and the presence of the ketone radical at the acidic moiety of the ester were necessary for the anticholinesterase action. 1- Methylheptyl -gamma- bromoacetoacetate formed a complex with acetylcholinesterase or butyrylcholinesterase without hydrolysis of its own molecule.