Heterogeneity and partial purification of human erythrocyte membrane acetylcholinesterase

Triton X-100 solubilised human erythrocyte acetylcholinesterase (E0), when subjected to chromatography on Sephadex G-200, showed one enzyme activity peak (Eg) and a number of protein peaks (Pg). The same sample could be separated into several subfractions of enzyme activity on DEAE-cellulose by gradient elution with increasing sodium chloride. When the gel filtered enzyme peak (Eg) alone was rechromatographed on an ion-exchange column under identical conditions, it showed only one enzyme peak. But when Eg in combination with protein peaks (Pg) without enzyme activity is rechromatographed as a physical mixture on a DEAE-cellulose column under the same conditions, the preparation could again be resolved into at least two fractions with enzyme activity. 2) Disc electrophoresis of fractions from DEAE-cellulose chromatography separated multiple bands which differ significantly from those produced by electrophoresis of E0. This suggests that E0 had undergone some form of conformational modification during the ion-exchange chromatography. However, this modification of E0 was avoided, if it was subjected to Sephadex G-200 chromatography before the DEAE-cellulose step. 3) A three-step technique (fractionation on Sephadex G-200, DEAE-cellulose chromatography and electrofocusing) has been performed for the purification of erythrocyte acetylcholinesterase. An enzyme preparation of high purity with a specific activity of 81 U/mg of protein was obtained.