Limited tryptic hydrolysis of legumin from faba bean (Vicia faba L.): formation of an [unequal] subunit pattern

One-dimensional and two-dimensional SDS-PAGE and Hydrophobic Cluster Analysis (HCA) were used for investigating the course of limited tryptic hydrolysis of faba bean legumin. SDS-PAGE revealed the formation of an “unequal” subunit pattern, characterized by 30 and 50 kDa subunits, which could be related to the A- and B-type subunits of legumin. These subunits followed different pathways during the non-cooperative part of the tryptic hydrolysis. HCA revealed structural differences between the subunit types and gave arguments to predicted potential splitting sites. A- and B-subunits differ in extension and composition of the flexible segments as well as in the interior of the C-terminal side, as in the C-termini of the α-chains which confirmed the observed non-uniform hydrolysis pattern. The HCA plot demonstrated that the number and exposition of flexible surface elements was changed by limited hydrolysis. This result was discussed with regard to the influence of tryptic modification on the emulsifying properties of legumin.