A reevaluation of choline acetyltransferase activity in human cerebrospinal fluid and serum.

Choline acetyltransferase (EC 2.3.1.6) was studied in human cerebrospinal fluid and blood. Sensitivity, precision and reproducibility of the radioactive assay were evaluated with a homogenate from pig brain and with partially purified enzymes from bovine brain and human placenta. Contrary to other reports, with the assay used in the present study, choline acetyltransferase activity was not detectable in the cerebrospinal fluid or blood of 50 patients with various neurological disorders. Only a very slight but significant non-enzymatic formation of a radioactive product by concentrated cerebrospinal fluid was observed. Nonenzymatic but enzyme-like formation of acetylcholine by thiol reagents and other compounds is discussed.