Preparation and characterization of two isozymes of choline acetyltransferase from squid head ganglia.

Two isozymes of choline acetyltransferase (Acetyl-CoA:choline O-acetyltransferase, EC 2.3.1.6) have been isolated and purified from squid head ganglia. Each isozyme contains multiple isoelectric forms with isoelectric points ranging from pH 5.0 to 6.2. The isozymes differ in their affinities for cellulose phosphate on column chromatography, as well as in their heat stabilities and in their capacities to be activated by salt. Both isozymes are stabilized by sucrose and by sulfhydryl-protecting reagents such as mercaptoethanol and dithiothreitol.