Glycinin

Glycinin, also called 11S globulin, is a major seed storage protein in soybeans (Glycine max). It comprises a substantial portion of the total seed protein and serves as a nitrogen reserve that supports germination and early growth.

Structure and composition: Glycinin belongs to the 11S globulin family. It is produced as a single precursor polypeptide that is post-translationally cleaved into an acidic subunit and a basic subunit, which remain linked by disulfide bonds. The mature protein assembles into a hexamer containing three acidic and three basic subunits, forming a compact, globular complex.

Genetics and biosynthesis: The glycinin family is encoded by a multi-gene set in the soybean genome. Expression is seed-specific and coordinated with other storage proteins during maturation. Assembly occurs within protein bodies in the cotyledons as the seed dries.

Nutrition and health aspects: Glycinin provides essential amino acids and contributes to the overall nutritional quality and digestibility of soybean proteins. It is a recognized allergen in soy products, with IgE-mediated responses in a subset of individuals. Processing methods such as heat treatment, fermentation, and enzymatic hydrolysis can reduce, but not always eliminate, allergenicity.

Applications and occurrence: While most abundant in soybeans, glycinin is also present in related legume seeds as part of the 11S globulin class. In food systems, glycinin contributes functional properties of soy proteins, including emulsification and foaming, and is a major component of commercial soy protein isolates and concentrates.