Comparative study of enzymatic hydrolysis of α/β- and γ-gliadins

Enzymatic hydrolysis of proteins and fractionation of hydrolysates is a route of diversifying their functional properties. Chymotryptic hydrolysis of different sulphur-rich gliadins (α/β- and γ-types), major wheat storage proteins, was studied. The peptides formed in the course of digestion were characterised by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate (SDS-PAGE) and reversed-phase high performance liquid chromatography (RP-HPLC). With reference to previous work, a general scheme of degradation was assessed for γ-gliadins. Limited hydrolysis released two types of polypeptides, comprising respectively the repetitive and the non-repetitive moieties of the protein. In spite of strong sequence homologies between the two groups of sulphur-rich gliadins, it was not possible to prepare similar peptide fractions from α/β-gliadins. They were more resistant to hydrolysis and the region where the two domains merge appeared inaccessible to chymotrypsin. Restricted accessibility of cleavage sites was attributed to the less expanded conformation of α/β-type than γ-type gliadins. A first step of scaling-up was performed. This offers opportunities to prepare functional peptides from wheat storage proteins.