Effect of Saccharide Structure and Size on the Degree of Substitution and Product Dispersity of α-Lactalbumin Glycated via the Maillard Reaction

The course of the Mallard reaction between a-lactalbumin and various mono- and oligosaccharides in the solid state was studied using UPLC-ESI-TOF-MS. Individual reaction products were monitored for their degree of substitution per protein molecule (DSP). The Mallard reaction rate depended on the saccharide type and when the saccharide size increased. Conjugation with charged saccharides was hindered when a specific average DSP was reached, probably resulting from electrostatic repulsion. The DSP varied between 0 and 15, and the standard deviation of average DSP, which is a measure for product dispersity, increased to 1.9. Similar experiments were performed with a dipeptide. Relative reaction rates in these experiments were 1 for glucose, 0.28 for maltose, and 0.16 for maltotriose. Comparison of the results Obtained using a-lactalbumin and the dipeptide made clear that the Mallard reaction rate is determined by a number of factors, including saccharide reactivity and lysine accessibility.