The purification of choline acetyltransferase of squid-head ganglia

Choline acetyltransferase (EC 2.3.1.6) isolated from the head ganglia of squid could be purified by use of mercurial-Sepharose columns as well as Sepharose columns to which the enzyme inhibitor p-(m-bromophenyl)vinyl pyridinium had been attached. These columns, in conjunction with 30-55% ammonium sulfate precipitation, 40-30% ammonium sulfate extraction, chromatography on sulfopropyl-Sephadex and on cellulose phosphate and hydroxylapatite columns, led to the isolation of three factions of choline acetyltransferase ranging in activity from 1000 to 4000 mumole/mg of protein/per hr. Polyacrylamide gel electrophoresis suggests that two of these fractions are homogeneous. The squid choline acetyltransferase is different from the mammalian-brain enzymes in having a larger molecular weight under the conditions used and in being relatively poorly inhibited by styryl pyridinium compounds.