Food and Drug Department, University of Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy.
Centro Interdipartimentale Misure (CIM), University of Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy.
Molecules. 2020 Mar 12;25(6):1294. doi: 10.3390/molecules25061294.
The high temperatures used in the production of milk may induce modifications in proteins structure. Due to occurrence of the Maillard reaction, lactose binds lysine residues in proteins, affecting the nutritional value. Milk is also an important source of allergenic proteins (i.e., caseins, β-lactoglobulin and α-lactalbumin). Thus, this modification may also affect the allergenicity of these proteins. Focusing on milk whey proteins, a screening on different Ultra High Temperatures (UHT) and pasteurized milk samples was performed to identify lactosylation sites, in particular in protein known epitopes, and to verify the correlation between lactosylation and the harshness of the treatment. Whey proteins were extracted from milk samples after caseins precipitations at pH 4.6 and, after chymotryptic and tryptic in solution digestion, peptides were analysed by UPLC-MS and LTQ-Orbitrap. Results show the presence of lactosylated lysine residues in several known epitopes. Then, a β-lactoglobulin epitope was selected and synthesized by solid phase synthesis followed by in solution lactosylation, obtaining high reaction yields and purities. The synthesis of lactosylated allergenic epitopes, described here for the first time, is a useful tool for further studies on the technological impacts on food allergenicity.
高温生产牛奶可能会导致蛋白质结构发生变化。由于美拉德反应的发生，乳糖会与蛋白质中的赖氨酸结合，从而影响其营养价值。牛奶也是过敏原蛋白（如酪蛋白、β-乳球蛋白和α-乳白蛋白）的重要来源。因此，这种修饰也可能影响这些蛋白质的致敏性。本文专注于乳清蛋白，对不同的超高温（UHT）和巴氏杀菌乳样品进行了筛选，以鉴定乳糖基化位点，特别是在蛋白质已知表位中，并验证乳糖基化与处理强度之间的相关性。在 pH 4.6 下沉淀酪蛋白后，从乳样中提取乳清蛋白，然后在溶液中进行糜蛋白酶和胰蛋白酶消化，通过 UPLC-MS 和 LTQ-Orbitrap 分析肽段。结果表明，在几个已知表位中存在乳糖化赖氨酸残基。然后，选择β-乳球蛋白表位进行固相合成，然后进行溶液内乳糖基化，得到高反应产率和纯度。本文首次描述了过敏原性表位的合成，这是进一步研究技术对食物致敏性影响的有用工具。
