Heat-induced amyloid-like aggregation of β-lactoglobulin affected by glycation by α-dicarbonyl compounds in a model study

摘要

BACKGROUND alpha-Dicarbonyl compounds are widely generated in the Maillard reaction, caramelization and oil oxidation during heat treatment. These compounds can readily react with lysine and arginine residues of a protein, whereas the influence of these compounds on protein structure and quality has seldom been revealed. This study compared influence of glycation by glucose and alpha-dicarbonyl compounds on amyloid-like aggregation of beta-lactoglobulin (beta-LG), both fibrillation kinetics and conformation of aggregates were studied. RESULTS Compared with glycation by glucose, the glycation by alpha-dicarbonyl compounds resulted in faster reduction of free amino group, sulfydryl group, and the relative content of beta-sheet secondary structure, according to the ultraviolet (UV) spectra or circular dichroism (CD) spectra results. Based on the analysis of fibrillation kinetics using thioflavin T (ThT) binding assay, the glycation by alpha-dicarbonyls were more efficient in suppressing the growth of fibrillar aggregates. In addition, glycation by alpha-dicarbonyl resulted in amorphous oligomers, which were compared with the amyloid-like aggregates in control and glucose-glycated samples, based on the transmission electron microscopy (TEM) observation. CONCLUSIONS Glycation by alpha-dicarbonyl compounds induced larger decline in the beta-sheet structure of beta-LG than glycation by glucose, and thus largely suppressed the amyloid-like aggregation of beta-LG and changed the morphology of aggregates.

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