Stereoselectivity of lipases. II. Stereoselective hydrolysis of triglycerides by gastric and pancreatic lipases

E Rogalska,S Ransac,R Verger

doi:10.1016/s0021-9258(17)30500-8

Abstract

In the present study, porcine pancreatic lipase, rabbit gastric lipase, and human gastric lipase stereospecificity toward chemically alike, but sterically nonequivalent ester groups within one single triglyceride molecule was investigated. Lipolysis reactions were carried out on synthetic trioctanoin or triolein, which are homogenous, prochiral triglycerides, chosen as models for physiological lipase substrates. Diglyceride mixtures resulting from lipolysis were derivatized with optically active R-(+)-1-phenylethylisocyanate, to give diastereomeric carbamate mixtures, which were further separated by high performance liquid chromatography. Resolution of diastereomeric carbamates gave enantiomeric excess values, which reflect the lipases stereobias and clearly demonstrate the existence of a stereopreference by both gastric lipases for the sn-3 position. The stereoselectivity of human and rabbit gastric lipases, expressed as the enantiomeric excess percentage, was 54% and 70% for trioctanoin and 74% and 47% for triolein, respectively. The corresponding values with porcine pancreatic lipase were 3% in the case of trioctanoin and 8% in that of triolein. It is worth noting that rabbit gastric lipase, unlike human gastric lipase, became more stereoselective for the triglyceride with shorter acyl chains (trioctanoin). This is one of the most striking catalytic differences observed between these two gastric lipases.

Highlights

In the present study, porcine pancreatic lipase, rabbit gastric lipase, and human gastric lipase stereospecificity toward chemically alike, but sterically nonequivalent ester groups within one single triglyceride molecule was investigated
Diglyceride mixtures resulting from lipolysis were derivatized with optically active R-(+)-1-phenylethylisocyanate, to give diastereomeric carbamate mixtures, which were further separated by high performance liquid chromatography
The stereoselectivity of PPL, RGL, and HGL was tested in trioctanoin and triolein lipolysis reactions by derivatizing the resulting diglycerides, according to the principle depicted in and the mixtures of enantiomeric diglycerides obtained were reacted with R-(+)-1-phenylethylisocyanate, to produce diastereomeric carbamates with a 100% yield

Summary

STEREOSELECTIVE HYDROLYSIS OF TRIGLYCERIDES BY GASTRIC AND PANCREATIC LIPASES*

From the Centre de Biochimie et de Biologic Moliculaire du Centre National de la Recherche Scientifique 31, Chemin Joseph Aiguier, 13402 Marseille Cedex 09, France. The reported [23, 24] preferential release of short chain and medium chain fatty acids by gastric lipase may be partly attributable to its stereoselectivity and to a lesser extent to a short chain fatty acid specificity The latter point of view was recently reinforced by Gargouri et al [25], who reported that purified human gastric lipase was able to hydrolyze both short and long chain triglycerides at comparable rates under acidic conditions. Diglycerides, generated in a partial enzymatic hydrolysis of synthetic triacylglycerols with three identical acyl chains, were reacted with R-(+)-1-phenylethylisocyanate, to give diastereomeric carbamate mixtures, resolved by Stereoselective Hydrolysis of Triglycerides by Digestive Lipases. This prompted us to use purified gastric and pancreatic lipases, which are the main lipases of the mammalian digestive tract, as biocatalysts

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