Inhibition of lipases by ∊-polylysine

Abstract

Oral administration of ∊-polylysine to rats reduced the peak plasma triacylglycerol concentration. In vitro, ∊-polylysine and polylysine strongly inhibited the hydrolysis, by either pancreatic lipase or carboxylester lipase, of trioleoylglycerol (TO) emulsified with phosphatidylcholine (PC) and taurocholate. The ∊-polylysine concentration required for complete inhibition of pancreatic lipase, 10 μg/ml, is 1,000 times lower than that of BSA required for the same effect. Inhibition requires the presence of bile salt and, unlike inhibition of lipase by other proteins, is not reversed by supramicellar concentrations of bile salt. Inhibition increases with the degree of polylysine polymerization, is independent of lipase concentration, is independent of pH between 5.0 and 9.5, and is accompanied by an inhibition of lipase binding to TO-PC emulsion particles. However, ∊-polylysine did not inhibit the hydrolysis by pancreatic lipase of TO emulsions prepared using anionic surfactants, TO hydrolysis catalyzed by lingual lipase, or the hydrolysis of a water-soluble substrate. In the presence of taurocholate, ∊-polylysine becomes surface active and adsorbs to TO-PC monomolecular films.These results are consistent with ∊-polylysine and taurocholate forming a surface-active complex that binds to emulsion particles, thereby retarding lipase adsorption and triacylglycerol hydrolysis both in vivo and in vitro.

Keywords

• basic peptide
• complex
• lipid emulsion
• lipid monolayer