title: Comprehensive analysis of nonenzymatic post-translational β-lactoglobulin modifications in processed milk by ultrahigh-performance liquid chromatography-tandem mass spectrometry.
abstract: Nonenzymatic post-translational protein modifications (nePTMs) result in changes of the protein structure that may severely influence physiological and technological protein functions. In the present study, ultrahigh-performance liquid chromatography-electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) was applied for the systematic identification and site-specific analysis of nePTMs of β-lactoglobulin in processed milk. For this purpose, β-lactoglobulin, which had been heated with lactose under conditions to force nePTM formation (7 d/60 °C), was screened for predicted modifications by using full scans and enhanced resolution scan experiments combined with enhanced product ion scans. Thus, the main glycation, glycoxidation, oxidation, and deamidation products of lysine, arginine, methionine, cysteine, tryptophan, and asparagine, as well as the N-terminus, were identified. Using these MS data, a very sensitive scheduled multiple reaction monitoring method suitable for the analysis of milk products was developed. Consequently, 14 different PTM structures on 25 binding sites of β-lactoglobulin were detected in different milk products.
authors.affiliation: Department of Chemistry and Pharmacy, Chair of Food Chemistry, Emil Fischer Center, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Jasmin
authors.initials: J
authors.lastname: Meltretter
authors.forename: Johannes
authors.initials: J
authors.lastname: Wüst
authors.forename: Monika
authors.initials: M
authors.lastname: Pischetsrieder
mesh_terms: D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005511:Food Handling; D006358:Hot Temperature; D007782:Lactoglobulins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D007785:Lactose / Q000378:metabolism; D008892:Milk / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000596:Amino Acids; D007782:Lactoglobulins; D007785:Lactose