Affinity electrophoresis, a new way of separating usual from atypical serum cholinesterases

Atypical serum cholinesterase is associated with prolonged recovery from normal doses of succinylcholine. Atypical (AA) and usual (UU) serum cholinesterases are electrophoretically identical; the 2 forms have been separated to date only by affinity chromatography on a column. Affinity electrophoresis introduces a new technique for this purpose. The affinity gel is made in a 0.5 x 6 cm tube in 3 layers: first 0.9 ml of 6% acrylamide are polymerized, secondly 0.1 ml 6% acrylamide containing in suspension affinity ligand bound to sepharose, and uppermost 0.1 ml concentrating gel. The affinity ligand is [N (6 aminocaproyl 6' aminocaproyl) p aminophenyl]trimethylammonium bromide hydrobromide bound to sepharose at a concentration of 3.6 μmoles per ml. After 5 hr electrophoresis at 5 mAmps per gel, the atypical enzyme migrates halfway down the gel (about 2.5 cm), whereas the usual cholinesterase remains bound to the affinity resin. The heterozygote (UA) can be clearly distinguished from AA and UU because it gives multiple bands. The heterozygote banding pattern confirms the fact that serum cholinesterase is primarily a tetramer and that serum of heterozygotes contains 5 tetrameric molecular species produced by random combination of usual and atypical subunits (La Du and Choi, Isozymes II (1975), Academic Press, p. 877). This technique should find a broad application in the search for variant enzymes which are not altered in charge but show an alteration of affinity for substrate.