Mechanism of the Reduced IgG/IgE Binding Abilities of Glycated β-Lactoglobulin and Its Digests through High-Resolution Mass Spectrometry.

Abstract

Glycation between proteins and reducing sugars is the common chemical modification in food protein, and many studies have focused on the allergenicity of the glycated protein. However, a systemic study on the allergenicity change of its digests is lacking. In this work, we explored the change rule of the digestibility and allergenicity of glycated β-Lg during in vitro gastrointestinal digestion and interpreted the mechanism using high-resolution mass spectrometry. Glycation with arabinose increased the resistance of β-Lg to digestive enzyme, with a low hydrolysis value. Indirect competitive ELISA showed that the IgG/IgE binding rates of β-Lg were reduced after glycation and further reduced after digestion, in comparison with the digests of unglycated β-Lg. There are two reasons for this phenomenon. On the one hand, 11 glycated sites were determined in the lowest allergenicity arabinose-β-Lg conjugation (Ara-β-Lg), which was distributed in the IgG and IgE linear allergic epitopes of β-Lg. On the other hand, glycation masking linear allergenic epitopes had a more significant effect on reducing allergenicity in comparison to digestive enzyme hydrolysis. These results indicated that the allergenicity of Ara-β-Lg in the human body might be lower than that of unglycated β-Lg.