Deciphering Changes in the Structure and IgE-Binding Ability of Ovalbumin Glycated by α-Dicarbonyl Compounds under...

Area of Science:

• Food Chemistry
• Protein Chemistry
• Allergenicity Studies

Background:

• The Maillard reaction (MR) significantly alters dietary proteins, but specific impacts of its intermediates and products on protein structure and allergenicity remain unclear.
• Ovalbumin (OVA), a common dietary protein, undergoes structural and antigenic changes via MR, necessitating investigation into specific modifications.
• Understanding these changes is crucial for assessing food safety and allergenicity, particularly concerning advanced glycation end-products (AGEs).

Purpose of the Study:

• To investigate the structural and IgE-binding property changes in ovalbumin (OVA) upon glycation by α-dicarbonyl compounds (α-DCs), key Maillard reaction intermediates.
• To analyze the impact of specific AGEs formed from different α-DCs (glyoxal, methylglyoxal, butanedione) on OVA structure and immunoreactivity.
• To correlate AGE formation with structural unfolding and reduced IgE-binding capacity of glycated ovalbumin (OVA-AGE).

Main Methods:

• Ovalbumin (OVA) was reacted with methylglyoxal (MGO), glyoxal (GO), and butanedione (BU) under simulated heating to generate glycated OVA (OVA-AGE).
• Quantification of 10 specific AGEs and total AGEs was performed, alongside analysis of protein conformational changes.
• IgE-binding and soluble form of Receptor for Advanced Glycation End-products (sRAGE) binding were assessed, with high-resolution mass spectrometry used to identify glycation sites on OVA.

Main Results:

• Glycation by α-DCs induced conformational unfolding in OVA, with reactivity order GO > MGO > BU.
• Total AGEs and specific AGEs like Nε-carboxymethyllysine increased with heating and α-DC concentration.
• Glycated OVA exhibited reduced IgE-binding but increased sRAGE-binding, correlating with AGE content and structural alterations.
• Mass spectrometry confirmed varied glycation sites (Lys, Arg residues) and their association with altered immunoreactive epitopes.

Conclusions:

• Glycation of ovalbumin by α-dicarbonyl compounds significantly alters its structure and reduces IgE-binding capacity, suggesting a modulation of its allergenic potential.
• The type and extent of AGE modification are dependent on the specific α-DC, temperature, and dosage, influencing the resulting structural and immunological properties.
• These findings provide critical insights into the biological consequences of Maillard reaction intermediates on dietary protein allergenicity and safety.