title: β-Lactoglobulin as nanotransporter--Part II: Characterization of the covalent protein modification by allicin and diallyl disulfide.
abstract: The whey protein β-lactoglobulin has been proposed as a transporter for covalent bound bioactive compounds in order to enhance their stability and reduce their sensory perception. The garlic derived compounds allicin and diallyl disulfide were bound covalently to the native and heat denatured protein. The binding site and the influence of the modification on the digestibility were determined by mass spectrometric analysis of the modified β-lactoglobulin. Further, the conformation of the modified protein was assessed by circular dichroism and dynamic light scattering. The free thiol group of Cys(121) turned out to be the major binding site. After proteolysis with trypsin at pH 7 but not with pepsin at pH 2, a limited transfer to other cysteinyl residues was observed. The covalently bound ligands did not mask any proteolytic cleavage sites of pepsin, trypsin or chymotrypsin. The modified β-lactoglobulin showed a native like conformation, besides a moderate loosening of protein folding. The covalent binding of organosulfur compounds to β-lactoglobulin provides a bioactive ingredient without impairing the digestibility and functional properties of the protein.
authors.affiliation: Institute of Human Nutrition and Food Science, Food Technology, Christian-Albrechts-Universität zu Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany. Electronic address: swilde@foodtech.uni-kiel.de.
authors.forename: Sandra Catharina
authors.initials: SC
authors.lastname: Wilde
authors.affiliation: Institute for Experimental Medicine, Division of Systematic Proteome Research, Christian-Albrechts-Universität zu Kiel, Niemannsweg 11, 24105 Kiel, Germany. Electronic address: c.treitz@iem.uni-kiel.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Treitz
authors.affiliation: Institute of Human Nutrition and Food Science, Food Technology, Christian-Albrechts-Universität zu Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany.
authors.forename: Julia Katharina
authors.initials: JK
authors.lastname: Keppler
authors.affiliation: Institute for Experimental Medicine, Division of Systematic Proteome Research, Christian-Albrechts-Universität zu Kiel, Niemannsweg 11, 24105 Kiel, Germany.
authors.forename: Tomas
authors.initials: T
authors.lastname: Koudelka
authors.affiliation: Institute of Human Nutrition and Food Science, Food Technology, Christian-Albrechts-Universität zu Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany.
authors.forename: Kalpana
authors.initials: K
authors.lastname: Palani
authors.affiliation: Institute for Experimental Medicine, Division of Systematic Proteome Research, Christian-Albrechts-Universität zu Kiel, Niemannsweg 11, 24105 Kiel, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Tholey
authors.affiliation: Institute of Nutritional Science, University of Potsdam, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany.
authors.forename: Harshadrai M
authors.initials: HM
authors.lastname: Rawel
authors.affiliation: Institute of Human Nutrition and Food Science, Food Technology, Christian-Albrechts-Universität zu Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Schwarz
mesh_terms: D000498:Allyl Compounds / Q000737:chemistry*; D002918:Chymotrypsin / Q000378:metabolism; D002942:Circular Dichroism; D004220:Disulfides / Q000737:chemistry*; D005737:Garlic; D007782:Lactoglobulins / Q000737:chemistry*; D008968:Molecular Conformation; D010434:Pepsin A / Q000378:metabolism; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013441:Sulfinic Acids / Q000737:chemistry*; D014357:Trypsin / Q000378:metabolism
chemical_list: D000498:Allyl Compounds; D004220:Disulfides; D007782:Lactoglobulins; D013438:Sulfhydryl Compounds; D013441:Sulfinic Acids; C006452:allicin; C028009:diallyl disulfide; D002918:Chymotrypsin; D014357:Trypsin; D010434:Pepsin A
keywords: Allicin; Beta-lactoglobulin; CD, DLS; Covalent modification; Diallyl disulfide; Garlic; LC–MS; Thiol