A comparative study of non-enzymatic glycation of Lysozyme by two glycating agents: methylglyoxal and glycolaldehyde

Non-enzymatic glycation of proteins is a post-translational modification process which plays an important role in diabetes mellitus [1]. It involves covalent bond formation between free amino groups of proteins and reducing sugars that affects the physical and functional properties of proteins [2]. The present study was aimed at the investigation of the effects of glycation of hen egg white lysozyme (HEWL) by methylglyoxal and glycolaldehyde. The objectives of this study were to evaluate the enzyme activity during the glycation process, to identify the structures of advanced glycation end products (AGEs) formed on glycated HEWL, to investigate the effect of glycation on the secondary structure of glycated HEWL, and to analyse the morphology of the resulting aggregates. By using interdisciplinary techniques, we have shown that the kinetic rate of enzymatic activity loss of HEWL by methylglyoxal is two times higher than that for glycolaldehyde. Nevertheless, no changes in the secondary structure of HEWL were detected by CD. Furthermore, AGEs formed in the glycated HEWL by methylglyoxal promotes cross-linking in the glycated enzyme. Finally, the resulting aggregates exhibit the same spherical morphology but with different size (glycolaldehyde induces formation of bigger aggregates).