Fogliano V, Monti S M, Visconti A, Randazzo G, Facchiano A M, Colonna G, Ritieni A
Dipartimento di Scienza degli Alimenti, Università di Napoli 'Federico II', Parco Gussone, 80055 Portici, Naples, Italy.
Biochim Biophys Acta. 1998 Nov 10;1388(2):295-304. doi: 10.1016/s0167-4838(98)00177-0.
Thermal treatment of milk leads to non-enzymatic glycosylation of proteins through Maillard reaction. Free NH2 groups of basic amino acids react with the reducing carbonyl group of lactose forming the so-called Amadori products. Electrospray mass spectrometry analysis shows that beta-lactoglobulin (beta-LG), the major whey protein, undergoes lactosylation under industrial thermal treatment. In order to investigate the specificity of reactive sites for lactose binding the analysis of trypsin hydrolysates of beta-LG isolated from different industrial milks was performed. Results demonstrate that Lys-100 is a preferential lactosylation site of beta-LG during industrial milk treatment. These results were confirmed by an analysis of the three-dimensional model of the protein which showed that Lys-100 had the highest solvent accessibility and proximity to another amino group making Lys-100 the best candidate to lactosylation. Lys-47, previously identified by other authors, showed a good proximity to another Lys residue, but an intermediate level of exposition to solvent.
牛奶的热处理会通过美拉德反应导致蛋白质的非酶糖基化。碱性氨基酸的游离氨基与乳糖的还原性羰基反应，形成所谓的阿马多里产物。电喷雾质谱分析表明，主要的乳清蛋白β-乳球蛋白（β-LG）在工业热处理下会发生乳糖基化。为了研究乳糖结合反应位点的特异性，对从不同工业牛奶中分离出的β-LG的胰蛋白酶水解产物进行了分析。结果表明，在工业牛奶处理过程中，Lys-100是β-LG优先发生乳糖基化的位点。对该蛋白质三维模型的分析证实了这些结果，该分析表明Lys-100具有最高的溶剂可及性，并且靠近另一个氨基，这使得Lys-100成为乳糖基化的最佳候选位点。其他作者先前鉴定出的Lys-47显示出与另一个Lys残基的良好接近性，但暴露于溶剂中的水平处于中等。
