Structure-function relationships of soybean proteins revealed by using recombinant systems

Glycinin and β-conglycinin are the major storage proteins of soybean and determine the functional properties of soybean proteins. Structure-function relationships of glycinin and β-conglycinin were investigated by using Escherichia coli expression systems. Examination of functional properties of various modified versions of proglycinin A1aB1b suggests that the hydrophobicity of the C-terminal region is probably important for a high emulsifying ability, that the topology of free SH residues is closely related to the heat-induced gel forming ability and that the structural factors suitable for gelation and emulsification properties are quite different. Mutual comparison of functional properties of β-conglycinin constituent subunits (α, α′ and β) and the core regions of α and α′ indicate that the core regions determine thermal stability and surface hydrophobicity, that the extension regions of α and α′ contribute to high solubility and emulsifying abilities and that the carbohydrate moieties inhibit the formation of heat-induced aggregates. Analyses by chimerization of glycinin and β-conglycinin suggest that structure-function relationships are different between glycinin and β-conglycinin.