Inhibition of human pancreatic lipase by tetrahydrolipstatin: Further kinetic studies showing its reversibility

Ali Tiss, H. Lengsfeld, F. Carrière, R. Verger

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

Tetrahydrolipstatin (THL, Orlistat) is a potent inhibitor of gastrointestinal lipases. Using the pH-stat technique we report that, in the absence of substrate, THL (at a molar excess of 100) inhibits rapidly (after few minutes of incubation) human pancreatic lipase (HPL). Bile salts over their critical micellar concentration (CMC) were found to accelerate the inhibition process. At variance with the generally accepted model of a covalent and quasi-irreversible acyl-lipase complex, we showed here that the inhibition of HPL could be rapidly and partially reversed in the presence of an emulsion of short- or long-chain triacylglycerols, as indicated by a kinetic reactivation process. The presence of bile salts in the incubation medium, containing THL and HPL, was found to stabilise the covalent complex as reflected by a decrease in the reactivation rate. Paradoxically, the presence of bile salts in the lipase assay enhanced this reactivation process probably by forming mixed micelles between bile salts and THL, which accelerates the deacylation phenomenon. On the basis of this kinetic study, a general model is proposed to describe the inhibition of lipases by THL in the aqueous phase as well as its partial reactivation process at the lipid-water interface.

Original languageEnglish
Pages (from-to)41-47
Number of pages7
JournalJournal of Molecular Catalysis B: Enzymatic
Volume58
Issue number1-4
DOIs
Publication statusPublished - 1 Jun 2009

Keywords

  • Bile salt
  • Inhibition
  • Orlistat
  • Pancreatic lipase
  • Reactivation
  • Tetrahydrolipstatin

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