Serum cholinesterase: Function in lipoprotein metabolism

Summary Human serum beta-lipoproteins, isolated by percipitation with heparin-calcium mixture, showed cholinesterase activity. The enzyme activity was almost proportional to the lipoprotein concentration. Rats, treated with neostigmine, a cholinesterase inhibitor, showed a significant decrease in serum beta-lipoprotein and in the incorporation of H³-lysine into the lipoprotein compared to untreated controls. The decreased incorporation of H³-lysine into beta-lipoprotein was associated with increased labelling of alpha-lipoprotein. There was no significant difference in the labelling of pre-beta-lipoprotein. We propose that LDL is formed from VLDL in the presence of cholinesterase.We thank Dr C. J. Hutton for helpful discussions, Miss Patricia Fontaine for technical assistance, and Miss Patricia Candow and Mrs Barbara English for secretarial work. Supported by the Canadian Heart Foundation.