Phosphorylcholine: a specific promoter of reparin and serum -lipoprotein interaction

The mechanism of formation of heparin-β-lipoprotein complex was studied. Precipitation of fatty acid labelled β-lipoproteins and optical density changes of the reaction were used as measures for the formation of insoluble complex. Equimolar amounts of Ca-phosphorylcholine were found to be more effective than CaCl₂ to form the insoluble complex. In presence of 10 mM CaCl₂, minute amounts (2–16 μM) of Ca or Na-phosphorylcholine increased the interaction between heparin and serum β-lipoprotein. Equimolar amounts of choline, ethanolamine, acetylcholine, phosphoserine, phosphothreonine, α-glycerophosphate, α-glycerophosphate plus choline, NaH₂PO₄, galactose, glucosamine and N-acetylglucosamine had no effect on the reaction. The results suggested that phosphorylated quaternary nitrogen groups play a role in the interaction of β-lipoprotein with heparin and divalent cation.