Combined Effect of a Lecithin and a Bile Salt on Pancreatic Lipase Activity

Abstract

Lipolysis is regulated by the presence of amphiphilic compounds such as bile salts and lecithin, which are adsorbed at the triglyceride–water interface and therefore influence the approach of water-soluble pancreatic lipase to its insoluble substrate (emulsified triglycerides). The partition of bile salts between the lipid and the aqueous phase is of prime importance in the expression of lipase activity. Lipase activity was determined as a function of different combinations of concentrations of deoxycholate and dipalmitoylphosphatidyl choline. From ζ-potential measurements, it is evident that lecithin affects the partition of bile salts, most probably by displacing deoxycholate molecules. Our results indicate that lecithin cannot be classified a priori as inhibitor or activator of pancreatic lipase. As an amphiphilic compound, lecithin exerts a synergistic effect with bile salts via the formation of mixed micelles. The final effect on lipolysis depends on the ratio of lecithin to bile salt: low ratios enhance enzyme activity, whereas high ratios lead to inhibition.