Abstract:

Purposes: To study the structural changes of β-lactoglobulin (β-lg) after glycation induced by reducing sugar or
dicarbonyl compounds. Methods: The content of dicarbonyl compounds produced from β-lg and lactose was determined by
gas chromatography. The structural changes of β-lg caused by glycation initiated by different active carbonyl groups were
evaluated by ultraviolet (UV)-visible spectrophotometry, circular dichroism and size exclusion chromatography. Results:
Dicarbonyl compounds were produced by β-lg glycation. The contents of methylglyoxal and glyoxalall reached the highest
levels at 207 μg/g and 180 μg/g respectively after heating for 30 minutes. Then, the quantity of dicarbonyl compounds
began to decline, and remained at approximately 150 μg/g. The UV-visible and circular dichroism spectra showed effective
transformation of β-sheet to α-helix induced by glycation. By Sephadex G-75 sizeexclusion chromatography, a new
absorption peak was detected between 120 and 190 min, indicating the occurrence of β-lg glycation. Conclusion: Reducing
sugar and dicarbonyl compounds have a very strong role in β-lg glycation reaction and consequently may change the
structure of β-lg significantly.

Key words: β-lactoglobulin, circular dichroism, dicarbonyl compounds, structure