Lipolytic Enzymes of the Gastrointestinal Tract

Abstract

Several important points seem to have been underestimated during gastrointestinal lipolysis studies. First, it is evident that only low mechanical forces are responsible for fat emulsification in vivo. It was reported that the fraction of dietary triacylglycerols hydrolyzed and adsorbed in vivo was higher following the ingestion of an emulsified meal than after ingesting a similar quantity of unemulsified fat. The existence of a lingual lipase suggests that triacylglycerol hydrolysis occurs to a certain extent in the stomach. It was proposed that this reaction is the first step in dietary fat digestion and that the amphiphilic lipids resulting therefrom facilitate triacylglycerol emulsification (1). This was directly confirmed by Linthorst et al. (2), who showed that the combination of bile salts and lipolytic products present in the intestine participated in the emulsification of triacylglycerols with low shear forces. Another important consequence of the significant prehydrolysis of alimentary triglycerides by a pregastric esterase is that diglycerides are probably more appropriate physiological substrates than triglycerides for pancreatic lipase.