Inhibition of lipases by ∊-polylysine

Takahiro Tsujita,Maho Sumiyoshi,Takeshi Takaku,William E Momsen,Mark E Lowe,Howard L Brockman

doi:10.1194/jlr.m300151-jlr200

Abstract

Oral administration of epsilon-polylysine to rats reduced the peak plasma triacylglycerol concentration. In vitro, epsilon-polylysine and polylysine strongly inhibited the hydrolysis, by either pancreatic lipase or carboxylester lipase, of trioleoylglycerol (TO) emulsified with phosphatidylcholine (PC) and taurocholate. The epsilon-polylysine concentration required for complete inhibition of pancreatic lipase, 10 microg/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, epsilon-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, epsilon-polylysine becomes surface active and adsorbs to TO-PC monomolecular films. These results are consistent with epsilon-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.

Highlights

Oral administration of ␧-polylysine to rats reduced the peak plasma triacylglycerol concentration
Two hours after ␧-polylysine administration, the plasma triacylglycerol concentration was decreased as compared with controls, but values were comparable after 4 h, 6 h, and 8 h
To determine if the effect on triglyceride levels in the serum could be due to impaired triglyceride hydrolysis in the intestine, the hydrolytic activity of rat pancreatic lipase toward TO emulsified with taurocholate (0.265 ␮M) and soybean PC was determined in the presence of increasing concentrations of ␧-polylysine (Fig. 2). ␧-Polylysine inhibited TO hydrolysis strongly; activity fell by Ͼ90% between 0.2 and 0.4 ␮M (1–2 ␮g/ml), and hydrolysis was completely inhibited at 2 ␮M (10 ␮g/ml)

Summary

Introduction

Oral administration of ␧-polylysine to rats reduced the peak plasma triacylglycerol concentration. 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.—Tsujita, T., M. It is well known that bile salts and synthetic detergents behave as inhibitors of lipolysis [3, 4] Amphiphilic proteins, such as BSA and ␤-lactoglobulin, have been shown to inhibit lipase activity toward its triglyceride substrate [5, 6]. We demonstrated that a basic protein, protamine, strongly inhibited the hydrolysis of trioleoylglycerol (TO) emulsified with phosphatidylcholine (PC) [7]. The experiments presented in this report were undertaken to evaluate this possibility and elucidate its mode of action

Methods

Results

Conclusion