1. A simple new assay for glycerylphosphorylcholine phosphodiesterase is described, in which radioactive glycerylphosphorylcholine is used as substrate and the reaction products are separated by adsorption on an anion-exchange resin. 2. Rat liver subcellular fractions contained both particulate (58%) and soluble (42%) glycerylphosphorylcholine phosphodiesterase. Both activities released free choline from glycerylphosphorylcholine. 3. The particulate glycerylphosphorylcholine phosphodiesterase was recovered mainly in the nuclear and microsomal fractions and showed a distribution similar to those of 5′-nucleotidase and alkaline phosphodiesterase I, both of which are constituents of the liver plasma membrane. 4. During purification of plasma membranes glycerylphosphorylcholine phosphodiesterase, 5′-nucleotidase and alkaline phosphodiesterase I showed largely similar behaviour, indicating that glycerylphosphorylcholine phosphodiesterase is also localized in liver plasma membranes. Slight differences in the distributions of these three enzymes in density-gradient separations are discussed in relation to the possibility that they are unevenly distributed on different areas of the cell surface. 5. The differences between glycerylphosphorylcholine phosphodiesterase and alkaline phosphodiesterase I indicate that these two activities are not functions of a single enzyme. 6. The glycerylphosphorylcholine phosphodiesterase of liver plasma membranes has a pH optimum of 8.5 and a Km for glycerylphosphorylcholine of 0.95mm. It is inhibited by EDTA and fully reactivated by a variety of bivalent cations (and Fe3+).
Glycerylphosphorylcholine phosphodiesterase in rat liver. Subcellular distribution and localization in plasma membranes
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Katherine A. Lloyd-Davies, Robert H. Michell, Roger Coleman; Glycerylphosphorylcholine phosphodiesterase in rat liver. Subcellular distribution and localization in plasma membranes. Biochem J 1 April 1972; 127 (2): 357–368. doi: https://doi.org/10.1042/bj1270357
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