Inhibition of Pancreatic and Microbial Lipases by Proteins: Kinetic and Binding Studies

Abstract

It has been established by many authors that bile salts are strong inhibitors of pancreatic (1,2) and microbial (3) lipases activity. Kinetic studies performed with emulsions of triacylglycerol as lipase substrate have shown that other amphiphiles such as synthetic detergents (4,5) or proteins (6–10) are also inhibitors of pancreatic lipase. With emulsified systems, it is difficult to assess the distribution of soluble versus adsorbed amphiphiles molecules. This prompted us to use the mono—layer technique based on surface pressure decrease consecutive to lipid film hydrolysis (8,9). Dicaprin was selected as substrate firstly to evaluate the influence of various proteins (β—lactoglobulin A, melittin, BSA, protein inhibiting lipase isolated from soybean (PIL) and ovalbumin) on the activity of pancreatic and microbial lipases, secondly to determine the amounts of radiolabeled enzyme and inhibitory protein bound to the lipid monolayer during lipolysis.