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

Abstract BACKGROUND α‐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 α‐dicarbonyl compounds on amyloid‐like aggregation of β‐lactoglobulin (β‐LG), both fibrillation kinetics and conformation of aggregates were studied. RESULTS Compared with glycation by glucose, the glycation by α‐dicarbonyl compounds resulted in faster reduction of free amino group, sulfydryl group, and the relative content of β‐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 α‐dicarbonyls were more efficient in suppressing the growth of fibrillar aggregates. In addition, glycation by α‐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 α‐dicarbonyl compounds induced larger decline in the β‐sheet structure of β‐LG than glycation by glucose, and thus largely suppressed the amyloid‐like aggregation of β‐LG and changed the morphology of aggregates. © 2019 Society of Chemical Industry