State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, Jiangxi, 330047, P. R. China.
Food Funct. 2018 Jan 24;9(1):417-425. doi: 10.1039/c7fo01082f.
Bovine β-lactoglobulin (β-Lg) is a major allergen existing in milk and causes about 90% of IgE-mediated cow's milk allergies. Previous studies showed that pulsed electric field (PEF) treatment could partially unfold the protein, which may contribute to the improvement of protein glycation. In this study, the effect of PEF pretreatment combined with glycation on the IgG/IgE-binding ability and the structure of β-Lg was investigated. The result showed that PEF pretreatment combined with glycation significantly reduced the IgG and IgE binding abilities, which was attributed to the changes of secondary and tertiary structure and the increase in glycation sites and degree of substitution per peptide (DSP) value determined by electron capture dissociation Fourier transform ion cyclotron resonance mass spectrometry (ECD/FTICR-MS). Unexpectedly, glycation sites (K47, K91 and K135) added by two mannose molecules were identified in glycated β-Lg with PEF pretreatment. Moreover, the results indicated that PEF pretreatment at 25 kV cm for 60 μs promoted the reduction of IgG/IgE-binding capacity by increasing the glycation degree of β-Lg, whereas single PEF treatment under the same conditions markedly enhanced the IgG/IgE-binding ability by partially unfolding the structure of β-Lg. The results suggested that ECD/FTICR-MS could help us to understand the mechanism of reduction in the IgG/IgE-binding of β-Lg by structural characterization at the molecular level. Therefore, PEF pretreatment combined with glycation may provide an alternative method for β-Lg desensitization.
牛β-乳球蛋白（β-Lg）是牛奶中的主要过敏原，约占 IgE 介导的牛奶过敏的 90%。先前的研究表明，脉冲电场（PEF）处理可以部分展开蛋白质，这可能有助于改善蛋白质糖化。在这项研究中，研究了 PEF 预处理与糖化结合对β-Lg 的 IgG/IgE 结合能力和结构的影响。结果表明，PEF 预处理与糖化结合显著降低了 IgG 和 IgE 的结合能力，这归因于二级和三级结构的变化以及电子俘获解离傅里叶变换离子回旋共振质谱（ECD/FTICR-MS）测定的糖化位点和取代度（DSP）值的增加。出乎意料的是，在经过 PEF 预处理的糖化β-Lg 中鉴定出了两个甘露糖分子添加的糖化位点（K47、K91 和 K135）。此外，结果表明，在 25 kV cm 下进行 60 μs 的 PEF 预处理通过增加β-Lg 的糖化程度促进了 IgG/IgE 结合能力的降低，而在相同条件下进行单次 PEF 处理则通过部分展开β-Lg 的结构显著增强了 IgG/IgE 结合能力。结果表明，ECD/FTICR-MS 可以通过在分子水平上进行结构表征来帮助我们了解降低β-Lg 的 IgG/IgE 结合能力的机制。因此，PEF 预处理与糖化结合可能为β-Lg 脱敏提供一种替代方法。
