title: Transglutaminase-mediated modification of glutamine and lysine residues in native bovine beta-lactoglobulin.
abstract: Bovine beta-lactoglobulin (BLG) is a major component in whey and its physical properties are important for the texture of many dairy-based foods. Modification of proteins with transglutaminase from Streptoverticillium mobaraense (MTGase) can be used to alter their physical properties. MTGase-mediated modification of native BLG was until now, however, not effective. Here we report a method that allows for the enzymatic modification of native BLG with MTGase. Lysines 8, 77, and 141 were modified with alpha-N-carbobenzyloxy-glutamine-glycine and glutamines 35, 59, 68,and 155 were modified with 6-aminohexanoic acid under nonreducing and nondenaturing conditions. MTGase-mediated BLG crosslinking is hampered by the low reactivity of the lysines and enzymatic deamidation of the glutamines prevails. Modification of BLG with poly-lysine yields a BLG derivative with increased affinity for the water-air interface and stronger surface tension lowering capacities than normal BLG. Hence, this modification method offers the opportunity to change the functional properties of BLG and to prepare novel protein foods.
authors.affiliation: TNO Nutrition and Food Research, Innovative Ingredients and Products, PO Box 360, NL-3700 AJ Zeist, The Netherlands. nieuwenhuizen@voeding.tno.nl
authors.forename: Willem F
authors.initials: WF
authors.lastname: Nieuwenhuizen
authors.forename: Henk L
authors.initials: HL
authors.lastname: Dekker
authors.forename: Toos
authors.initials: T
authors.lastname: Gröneveld
authors.forename: Chris G
authors.initials: CG
authors.lastname: de Koster
authors.forename: Govardus A H
authors.initials: GA
authors.lastname: de Jong
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D005973:Glutamine / Q000737:chemistry*; D007782:Lactoglobulins / Q000737:chemistry*; D008239:Lysine / Q000737:chemistry*; D008892:Milk / Q000737:chemistry*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013302:Streptomyces / Q000201:enzymology*; D013500:Surface Tension; D011503:Transglutaminases / Q000737:chemistry*
chemical_list: D007782:Lactoglobulins; D005973:Glutamine; D011503:Transglutaminases; D008239:Lysine