Hydrolysis of carnitine and choline esters by cholinesterases.

The hydrolysis of acetyl-dl-carnitylcholine, I-carnitylcholine and acetyl-dl-carnitine by the cholinester hydrolases was investigated. The ester bonds of acetyl-dl-carnitylcholine were hydrolyzed by the acetylcholinesterases (rat brain, human and bovine erythrocyte enzymes) to the extent of 25 per cent. The hydrolysis appeared to be stereospecific. Acetyl-dl-carnitylcholine was hydrolyzed slightly by purified human serum but not by fresh human plasma or purified horse serum cholinesterases. Several preparations of both acetylcholinesterase and cholinesterase failed to hydrolyze I-carnitylcholine and acetyl-dl-carnitine. These three compounds, as well as several other choline esters, competitively inhibited acetylcholinesterase hydrolysis of acetylthiocholine. Acetyl-dl-camitylcholine had marked affinity for acetylchol inesterase whereas acetyl-dl-carnitine and choline were very weak inhibitors. The products of hydrolysis of acetyl-dl-carnitylcholine by acetylcholinesterase were acetylcarnitine and choline. The significance of these end-products in metabolism is discussed