Glycation between ovalbumin (OVA)
and different monoses under mild dry heating at 37 °C was studied.
The content of free amino groups decreased dramatically, and the conformational
changes based on fluorescence and circular dichroism spectra were
evident in glycated OVA. The glycated sites and the average degree
of substitution per peptide molecule per site were determined using
liquid chromatography high-resolution mass spectrometry. Lysine and
arginine were the predominant glyaction sites, in which Lys207 was
a relatively reactive site for glycation in all of the conjugates.
In general, the extent of glycation of aldose was higher, and its
alterations on the steric layouts of protein were more drastic than
those of ketose. The configuration of hydroxyl groups at C-4 in sugar
epimers might be important for the glycation reactivity and conformational
modification in the glycated proteins. These insights would have important
implications for the creation of sweetened food products with desirable
structures and excellent quality control.
Ovalbumin (OVA) is one of the major
food allergens in hen eggs.
In this work, it was demonstrated that glycation with d-glucose
and its epimers, including d-mannose, d-allose, d-galactose, and l-idose, could effectively attenuate
the IgG/IgE binding of OVA, which was attributed to the covalent masking
by sugars and to its structural changes. The glycation sites were
determined, and their average degree of substitution was found using
liquid chromatography coupled with high-resolution mass spectrometry.
Fluctuations in OVA conformation were monitored by conventional spectrometry.
Compared to those of OVA-Man and OVA-Glu, OVA-All, OVA-Gal, and OVA-Ido
showed a higher glycation extent, and the alterations on their steric
layouts were more drastic, suggesting that the configuration of hydroxyl
groups at positions C-3, C-4, and C-5 in sugars might be important
for the glycation reactivity; as such, their capabilities in binding
with IgG/IgE decreased more significantly. Attempts were made to provide
valuable information for in-depth understanding of the differences
in biochemical functionality among epimeric sugars. These insights
would be helpful for designing sweetened food products with a desirable
level of safety.
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