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.

Mechanism on the Allergenicity Changes of α-Lactalbumin Treated by Sonication-Assisted Glycation during In Vitro Gastroduodenal Digestion

“…After pepsin digestion, MS/MS with HCD was performed to identify the glycated peptides. In theory, if a peptide is covalently bound with one d -galactose molecule, the corresponding m / z peak of the peptides will increase to 162, 81, and 54 at charges of +1, + 2, and +3 after losing a molecule of water . Similarly, when a peptide is covalently bound with two molecules of d -galactose, the m / z peak of the peptide could be 324 Da.…”

Maillard Reaction Induced Changes in Allergenicity of Food

“…However, our literature review showed that the possibility of glycation reducing the IgE binding capacity of β-lactoglobulin compared with the heating process seems to be related to the sugar type, reaction condition, and detection sera used. For example, when ribose, fructose, maltose, or arabinose was present, glycation further reduced the IgE binding capacity of β-lactoglobulin compared to heating, but reaction with lactose did not cause much difference because lactose induced a much lower glycation degree, and those glycated sites were not on main epitopes [ 29 , 30 ]. Under some dry and wet heating conditions, individual difference in the sera used even determines the increase or decrease in the IgE binding capacity [ 31 ]; see Table 1 for more detailed reaction conditions.…”

Effects of Superheated Steam Treatment on the Allergenicity and Structure of Chicken Egg Ovomucoid

“…The IgG binding rate was markedly influenced by high temperatures and long periods of treatments, with a maximum decline to 28% when treated at 200 °C for 10 min. The reduction in the IgG-binding ability of OVM may be due to the structural changes derived from amino acid modification and denaturation [ 15 ]. The results implied that SS-created extreme high temperatures of up to 200 °C might influence the protein structure and destroy IgG allergenicity epitopes.…”

“…SS treatment, particularly at high temperatures and long processing times, could induce the OVM aggregation, increase surface hydrophobicity, modify the functional groups and amino acids in OVM. These phenomena disrupted and buried some allergen epitopes and made it difficult for the combination of antibodies and antigens [ 14 , 15 ]. Therefore, the allergenicity of OVM was decreased and the anaphylactic reaction in the KU812 cell was inhibited.…”

“…The basophil histamine release test was carried out according to the method of Wang et al [ 15 ]. KU812 cells were cultured in RPMI-1640 medium with 20% fetal bovine serum (FBS) and 105 U/L penicillin/streptomycin for 24 h. A total of 5 × 10 5 cells was in each well.…”