As a complex reaction, biological
consequences of the Maillard
reaction (MR) on dietary proteins need to be deciphered. Despite previous
studies on the structural and antigenic properties of ovalbumin (OVA)
by MR, associated changes induced by specific MR intermediates and
their downstream products are largely unknown. This study focused
on the impacts of glycation by α-dicarbonyl compounds (α-DCs),
intermediates of MR and precursors of advanced glycation end-products
(AGEs), on the structural and IgE-binding properties of ovalbumin
(OVA) under simulated heating. Methylglyoxal (MGO), glyoxal (GO),
and butanedione (BU) were selected as typical α-DCs to generate
glycated OVA with different AGE-modifications (AGE-Ms). The results
showed that reactions between OVA and α-DCs generated OVA-AGE
with various degrees of modification and conformational unfolding,
and the reactivity of α-DCs followed the order GO > MGO >
BU.
Depending on the precursor type, the levels of 10 specific AGEs were
verified, and the amounts of total AGEs increased with heating temperature
and α-DC dosage. Compared to native OVA, glycated OVA showed
reduced IgE-binding levels but with sRAGE-binding ligands, the extent
of which was associated with the contents of total AGEs and Nε-carboxymethyllysine, and changes in certain protein
conformational structures. High-resolution mass spectrometry further
identified different AGE-Ms on the Lys and Arg residues of OVA, confirming
variations in the glycation sites and their associations with the
immunoreactive epitopes of OVA under different conditions.
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