Isoelectric point of native and sialidase-treated human-serum cholinesterase.

Abstract

1. 1. The electrophoretic mobility of native and sialidase-treated human-serum cholinesterase was determined by paper electrophoresis over the pH range 2.8–9.6; the determination included corrections for electro-osmosis, evaporation, apper-structure and adsorption of protein to the paper. The performance of the method was controlled with proteins of known mobility, orosomucoid and coeruloplasmin. 2. 2. The isoelectric point of native cholinesterase was found to be 2.9–3.0 and that of sialidase-treated cholinesterase 6.7–7.0. This is an agreement with previous findings that human-serum cholinesterase contains a large number of sialic acid residues in a terminal position. 3. 3. At pH 8.6 the electrophoretic mobility of native cholinesterase was −3.1·10−5 cm2/V/sec and that of sialidase-treated cholinesterase −0.2·10−5 cm 2/V/sec. 4. 4. Between pH 4 and 9.6 the mobility of sialidase-treated cholinesterase was 2.9·10−5 units above that of native cholinesterase. 5. 5. At pH 2.8 this difference decreased to about 2·10−5 units. 6. 6. It is suggested that the mobility-pH curve might be of value in the differentiation between closely related types of cholinesterases.