Glycation of α-lactalbumin with different size saccharides: Effect on protein structure and antigenicity

The effect of the size of saccharides on protein structure and antigenicity after glycation was studied. α-Lactalbumin (α-LA) was incubated in a dry state with glucose, maltose or maltooligosaccharides (up to maltopentaose), at 55 °C and 65% relative humidity. The extent of glycation, aggregation processes, antigenicity, glycation sites and structural changes were investigated. Structural changes were observed when the protein was incubated with larger saccharides. Furthermore, the degree of glycation decreased with an increase in the size of the saccharide. The antigenicity of all samples significantly decreased when glycation increased, but the greatest reduction of antigenicity was observed with maltotriose-α-LA. By comparing the glycation sites of all the glycated samples, glycation of Lys58 was dominant in glucose-α-LA and maltotriose-α-LA, whose antigenicity reductions were the highest. These results suggest that when the main epitope was glycated, the degree of antigenicity reduction increased with the increase in the size of the saccharide.