Étude des interactions β-Lactoglobuline bovine : peptides bioactifs et digestibilité in vitro des complexes

Authors: Roufik, Samira
Advisor: Gauthier, SylvieTurgeon, Sylvie
Other Title(s): Étude des interactions [bêta]-Lactoglobuline bovine
Abstract: Bovine β-lactoglobulin (β-Lg) contains numerous peptide sequences with biological activities, which have a high potential as nutraceutical ingredients. However, studies have demonstrated that some of these peptides, which are active during in vitro tests, loose their activity in animal models following oral ingestion, suggesting their enzymatic degradation during gastrointestinal transit. The aim of this work was to study β-Lg:bioactive peptide interactions and to investigate the in vitro digestibility of the resulting complexes. Firstly, it was shown that pepsic and chymotryptic digestions of some bioactive peptides varied according to the peptide chain length, the nature of the peptide and the presence of other peptides in the reaction medium. Using an ultrafiltration method, it was demonstrated that peptides β-Lg f102-105, f142-148 and f69-83 bind to β-Lg A in significant amounts corresponding to 1.5, 1.1 and 0.7 moles of peptides per mole of protein respectively. These results were validated by front-face fluorescence spectroscopy, which also provided evidences that the binding of the three peptides to β-Lg A modified the polarity of tryptophan environment in the protein structure. In addition, binding isotherms obtained by isothermal titration calorimetry showed that the binding of the antihypertensive peptide β-Lg f142-148 to β-Lg A followed a sequential three-site binding model with constants of associations of 2 X 103, 1 X 103 and 0.4 X 103 M-1 for the 1st, 2nd, and 3rd binding sites respectively. The enthalpy of binding was exothermic for the 1st and 2nd binding sites and endothermic for the 3rd binding site. Lastly, the in vitro digestibility of the protein and the complexes with pepsin, trypsin, chymotrypsin, and pancreatin showed that the complexes were hydrolyzed more slowly than the native protein by chymotrypsin or pepsin/chymotrypsin. The overall results support the hypothesis that the binding of bioactive peptides to β-Lg A could improve their resistance to proteolysis, and thus could contribute to maintain their structural integrity and bioactivity during gastrointestinal transit.
Document Type: Thèse de doctorat
Issue Date: 2005
Open Access Date: 11 April 2018
Permalink: http://hdl.handle.net/20.500.11794/18110
Grantor: Université Laval
Collection:Thèses et mémoires

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