α-乳白蛋白(α-LA)是牛乳中最主要的过敏原之一。该研究将不同糖链长度的糖(葡萄糖、麦芽糖、麦芽三糖、麦芽四糖、麦芽五糖)通过糖基化反应与α-LA结合,以评价糖链长度对α-LA糖基化产物抗原性的影响。结果表明,随糖链长度的增加,糖基化反应程度降低;同时α-LA的抗原性随糖基化反应时间的增长而降低,说明糖基化程度对于降低蛋白质抗原性起着十分重要的作用。然而在5种糖中麦芽三糖降低抗原性的效果最好,抗原抑制率达到51.67%,说明糖基化蛋白抗原性的降低,不仅受到糖基化程度的影响,而且与糖基化位点密切相关。对比5种还原糖的糖基化位点及其糖基化产物的抗原性,发现Lys58位点仅存在于抗原性降低最多的葡萄糖-α-LA和麦芽三糖-α-LA中。研究结果表明糖链长度可以影响糖基化位点,从而影响糖基化蛋白的抗原性,当主要的抗原表位被糖基化后,糖链长度越大,蛋白的抗原性降低效果越显著。

α-Lactalbumin(α-LA) is one of the main allergens in cow milk.In this study,α-LA was glycated with different size saccharides(glucose,maltose,maltotriose,maltotetraose and maltopentaose) to study the effect of the size of the saccharide on protein antigenicity.The results showed that,with an increase in the size of the saccharide,the degree of glycation decreased.The antigenicity of all glycated samples significantly decreased with an increase in incubation time,suggesting that the extent of glycation might be an important factor to decrease antigenicity.However,the largest reduction of antigenicity was observed after incubation with maltotriose,whose antigenicity declined by 51.67%.This could be related to the difference in binding specificity of the saccharides to the allergenic sites of the protein.Through comparing the glycation sites and the reduction of the antigenicity by incubating with the five saccharides,we found Lys58 may play an important role in the reduction of the antigenicity of α-LA.The results suggested that the glycation size could affect the glycation site,and eventually impact the antigenicity of the glycated protein.When the main epitope was glycated,the degree of antigenicity reduction increased with the increase in the size of the saccharide.