Malondialdehyde treatment reduced immunoreactivity of amandin and delayed its digestion

Objectives: The secondary products of lipid oxidation are one of the main factors inducing protein oxidation. The effects of oxidation treatment with malondialdehyde (MDA) on the immunoreactivity of amandin and its digestion were studied.Materials and Methods: The rabbit IgG binding ability of amandin was analyzed by western blotting, and the changes in amandin oxidation and immunoreactivity during digestion of amandin with different degrees of oxidation were investigated in combination with an almond allergen enzyme-linked immunosorbent assay kit. Alteration of linear epitopes of amandin by oxidation was investigated by liquid chromatography-tandem mass spectrometry (LC-MS/MS).Results: The results showed that the immunoreactivity of amandin was significantly reduced after 1 mmol/L MDA and 100 mmol/L MDA treatment. However, the 1 mmol/L MDA treatment was owing to cleavage of linear epitope peptide in amandin and oxidation of the active amino acid. The 100 mmol/L MDA treatment was due to aggregation of amandin and significant decrease in its solubility. Oxidation also reduced digestibility of amandin and significantly affected immunoreactivity during digestion. LC-MS/MS also identified four oxidation-prone methionine sites (aa 264-274, 298-308, 220-240, and 275-297) in gamma conglutinin 1.Conclusions: MDA treatment reduced the immunoreactivity of amandin. MDA treatment also led to protein aggregation, which slowed down the digestion of amandin and altered the immunoreactivity of amandin during digestion.