title: Cross-linking proteins by laccase-catalyzed oxidation: importance relative to other modifications.
abstract: Laccase-catalyzed oxidation was able to induce intermolecular cross-links in beta-lactoglobulin, and ferulic acid-mediated laccase-catalyzed oxidation was able to induce intermolecular cross-links in alpha-casein, whereas transglutaminase cross-linked only alpha-casein. In addition, different patterns of laccase-induced oxidative modifications were detected, including dityrosine formation, formation of fluorescent tryptophan oxidation products, and carbonyls derived from histidine, tryptophan, and methionine. Laccase-catalyzed oxidation as well as transglutaminase induced only minor changes in surface tension of the proteins, and the changes could not be correlated to protein cross-linking. The presence of ferulic acid was found to influence the effect of laccase, allowing laccase to form irreducible intermolecular cross-links in beta-lactoglobulin and resulting in proteins exercising higher surface tensions due to cross-linking as well as other oxidative modifications. The outcome of using ferulic acid-mediated laccase-catalyzed oxidation to modify the functional properties of proteinaceous food components or other biosystems is expected to be highly dependent on the protein composition, resulting in different changes of the functional properties.
authors.affiliation: Department of Food Science, Faculty of Agricultural Sciences, Aarhus University, Foulum, Tjele, Denmark. charlotte.l.steffensen@agrsci.dk
authors.forename: Charlotte L
authors.initials: CL
authors.lastname: Steffensen
authors.forename: Mogens L
authors.initials: ML
authors.lastname: Andersen
authors.forename: Peter E
authors.initials: PE
authors.lastname: Degn
authors.forename: Jacob H
authors.initials: JH
authors.lastname: Nielsen
mesh_terms: D002384:Catalysis; D003373:Coumaric Acids / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D042845:Laccase / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D011506:Proteins / Q000737:chemistry*; D055454:Trametes / Q000201:enzymology
chemical_list: D003373:Coumaric Acids; D003432:Cross-Linking Reagents; D005656:Fungal Proteins; D011506:Proteins; C004999:ferulic acid; D042845:Laccase