Le Thao T, Deeth Hilton C, Bhandari Bhesh, Alewood Paul F, Holland John W
School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia.
Food Chem. 2012 May 1;132(1):655-62. doi: 10.1016/j.foodchem.2011.11.012. Epub 2011 Nov 12.
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.
在乳制品的加工和储存过程中，乳蛋白会发生化学变化，如乳糖基化、脱酰胺作用和蛋白质交联。采用二维凝胶电泳和质谱联用的蛋白质组学技术，研究了浓缩乳清蛋白（MPC80）在储存过程中蛋白质的化学修饰。在二维凝胶上观察到了乳糖基化、脱酰胺作用和蛋白质交联。它们与储存温度、湿度和时间有关。乳糖基化的乳清蛋白在二维凝胶上以垂直的斑点堆叠形式得到了很好的分离。斑点的质量以324的倍数变化，表明乳糖与蛋白质中的赖氨酸残基相连。通过基质辅助激光解吸电离飞行时间质谱对α-乳白蛋白经胰蛋白酶消化后的斑点进行分析，结果表明存在多个乳糖基化位点。通过图像分析对凝胶上的乳糖加合物进行定量，从而能够监测加合物随时间的变化情况。结果表明，蛋白质组学可用于检测和定量储存的MPC80中蛋白质的化学修饰。
