Abstract:Using soybean as the raw material, the acidic and basic polypeptides of glycinin were isolated, and the differences between their effects in microbial transglutaminase (MTG)-mediated cross-linking were explored. Glycinin was obtained with a purity of more than 94% from soybean protein by isoelectric precipitation, gel filtration chromatography, and affinity chromatography. The acidic and basic polypeptides were isolated by isoelectric precipitation after heat denaturation and reduction with β-mercaptoethanol, and then characterized by electrophoresis and amino acid analysis. Furthermore, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and dissolution experiments were performed to determine the effects of acidic and basic polypeptides on enzymatic cross-linking and the solubility of the cross-linked products. The results suggested that both the acidic and basic polypeptides were effective substrates for MTG and could participate in the cross-linking reaction to form polymers with high molecular weight; however, the reaction rate of basic polypeptides was lower than that of acidic polypeptides. The differences between the acidic and basic polypeptides in the cross-linking reaction were slightly affected by the glutamine and lysine residue content, and were significantly affected by the hydrophobic amino acid content.
