Liver glycerylphosphorylcholine diesterase

Abstract

A method was developed for the rapid chemical preparation of L-[alpha]-glycerylphosphorylcholine (GPC) from ovolecithin. An enzyme was found in extracts prepared from acetone-dried rat liver which catalyzes the hydrolysis: L-[alpha]-GPC + H2O[long dash]>[alpha]-glycerophosphoric acid + choline. Similar extracts also attacked L-[alpha]-glycerylphosphorylethanolamine, and this diester was a competitive inhibitor of GPC hydrolysis. The GPC-splitting activity of such extracts was maximal at pH 7.5 and was stimulated by the addition of Mg2+(10-3 [image]). Similar concentrations of Mn2+ and Ca2+ were inhibitory, and this also applied to higher concentration of Mg2+. The enzyme was not sensitive to fluoride, iodoacetate, eserine or diiso-propylphosphorofluoridate. However, ethylenediaminetetraacetic acid (EDTA) and Zn2+ were strong inhibitors. Evidence was obtained for the presence of the enzyme in other tissues of the rat, but it is virtually absent from the liver of the sheep. Activity was not seen in rat plasma, but it was found in the blood corpuscles.