Cholinesterase was purified from human serum by a three-stage procedure involving chromatography on DEAE-cellulose at pH4.0, an electrofocusing technique and gel filtration on Sephadex G-200. The final product was purified 13000-fold with a yield of 54%, and only one protein and one cholinesterase band could be demonstrated by polyacrylamide-disc electrophoresis. The catalytic properties appeared to be unchanged by the purification procedure. The molecular weight was determined by both ultracentrifugation in a density gradient and gel filtration, and values close to 366000 were obtained. The isoelectric point of cholinesterase was estimated to be pH3.99. The method appears suitable for the preliminary purification of the rare genetic variants of human cholinesterase.
