Effects of Emulsifier Charge and Concentration on Pancreatic Lipolysis. 1. In the Absence of Bile Salts

摘要

An in vitro study is performed with sunflowernoil-in-water emulsions to clarify the effects of type of usednemulsifier, its concentration, and reaction time on the degreenof oil lipolysis, α. Anionic, nonionic, and cationic surfactantsnare studied as emulsifiers. For all systems, three regions arenobserved when surfactant concentration is scaled with thencritical micelle concentration, CS/cmc: (1) At CS < cmc, α ≈n0.5 after 30 min and increases up to 0.9 after 4 h. (2) At CS ≈ 3n× cmc, α ≈ 0.15 after 30 min and increases steeply up to 0.9nafter 2 h for the cationic and nonionic surfactants, whereas itnremains around 0.2 for the anionic surfactants. (3) At CS abovencertain threshold value, α = 0 for all studied surfactants, fornreaction time up to 8 h. Additional experiments show that the lipase hydrolyzes molecularly soluble substrate (tributirin) at CS ≫ncmc, which is a proof that these surfactants do not denature or block the enzyme active center. Thus, we conclude that thenmechanism of enzyme inhibition by these surfactants is the formation of a dense adsorption layer on an oil drop surface, whichndisplaces the lipase from direct contact with the triglycerides.