关键词: 大豆分离蛋白, 酶解, 抗原活性, 抗原表位, 肽

Abstract: The aim of this study was to investigate the changes in the molecular composition and antigenicity of soybean protein during its enzymatic hydrolysis and whether there could be antigenic epitope sequences in the hydrolysate. The enzyme used was alcalase. The changes in molecular composition and antigenicity were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and competitive enzyme-linked immunosorbent assay (ELISA), respectively. Some new peptides (i.e., 23 and 21 ku) were found in the hydrolysate and did not disappear even after 120 min of hydrolysis. Meanwhile the hydrolysate still retained 28% of the original antigenicity. In order to determine whether the new peptide chains were related to the antigenicity, the proteomic bands in the SDS-PAGE gel were hydrolyzed by trypsin and then analyzed by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). The amino acid sequences of the peptide fragments obtained were matched with the amino acid sequences in the antigen database and the soybean protein isolate database, respectively. The results showed that there were two complete sequence epitopes (LQRFNQRSPQLQNLR and SEDKPFNLRSRDPIYSNKLGKFFEITPEKN) in the 21 ku component, both of which came from the α subunit in β-conglycinin. The residual antigenicity of this peptide fragment was 15.7%. The amino acid sequences of the 23 ku peptide chain were matched partially with those of epitopes but no complete epitopes were found. However, its residual antigenicity was 2.1%. These findings may partially account for the antigenicity of soybean protein hydrolysates.

Key words: soybean protein isolate, hydrolysis, antigenicity, epitope, peptide