The conjugate prepared from (-)-epigallocatechin gallate (EGCG) and soy protein isolate (SPI) under alkaline and aerobic conditions was analyzed using a Nano-LC-Q-Orbitrap-MS/MS technique. The sulfhydryl and free amino groups of SPI were involved in covalent binding. Fifty-one peptides were conjugated with EGCG. Fifty-nine modified sites were identified, located on Cys, His, Arg, and Lys, respectively. It is the first time to confirm that each of the two phenolic rings of EGCG contained a reactive site that bound to an amino acid residue. The amino acid residue reactivity, amino acid sequence and composition affected the EGCG binding site in SPI. Lys and Arg residues are the most likely sites for modification, and modification appears to reduce IgE binding. This study is helpful to elucidate the pattern of covalent binding of polyphenols to proteins in food systems and provides a theoretical basis for the directional modification of soy proteins with polyphenols.

使用Nano-LC-Q-Orbitrap-MS / MS技术分析了在碱性和好氧条件下由（-）-表没食子儿茶素没食子酸酯（EGCG）和大豆分离蛋白（SPI）制备的结合物。SPI的巯基和游离氨基参与共价结合。51个肽与EGCG缀合。鉴定出59个修饰位点，分别位于Cys，His，Arg和Lys上。这是首次确认EGCG的两个酚环均含有一个与氨基酸残基结合的反应位点。氨基酸残基反应性，氨基酸序列和组成影响SPI中的EGCG结合位点。Lys和Arg残基是最可能的修饰位点，修饰似乎减少了IgE的结合。