title: A proteomic approach to detect lactosylation and other chemical changes in stored milk protein concentrate.
abstract: Milk proteins undergo chemical changes such as lactosylation, deamidation and protein cross-linking during processing and storage of milk products. A proteomic technique combining two-dimensional gel electrophoresis and mass spectrometry was used to investigate chemical modifications to proteins, in milk protein concentrate (MPC80), during storage. Lactosylation, deamidation and protein cross-linking were observed on 2-DE gels. They were storage temperature-, humidity- and time-dependent. Lactosylated whey proteins were well separated on 2-DE in vertical stacks of spots. The masses of the spots varied by multiples of 324, indicating the attachment of lactose to lysine residues in the proteins. The trypsin-digested spots of α-lactalbumin were analysed by MALDI-TOF mass spectrometry, which indicated multiple lactosylation sites. The lactose adducts on gels were quantified by image analysis, allowing development of adducts over time to be monitored. The results show that proteomics can be used for the detection and quantification of chemical modifications to proteins in stored MPC80.
authors.affiliation: School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Thao T
authors.initials: TT
authors.lastname: Le
authors.affiliation: School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Hilton C
authors.initials: HC
authors.lastname: Deeth
authors.affiliation: School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Bhesh
authors.initials: B
authors.lastname: Bhandari
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Paul F
authors.initials: PF
authors.lastname: Alewood
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia. Electronic address: j.holland@imb.uq.edu.au.
authors.forename: John W
authors.initials: JW
authors.lastname: Holland
mesh_terms: D000818:Animals; D002417:Cattle; D003432:Cross-Linking Reagents / Q000737:chemistry*; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods*; D007785:Lactose / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry*; D040901:Proteomics / Q000379:methods*
chemical_list: D003432:Cross-Linking Reagents; D008894:Milk Proteins; D007785:Lactose
keywords: Lactosylation; Milk protein concentrate (MPC80); Protein cross-linking; Two dimensional gel electrophoresis