ACTION OF TRANSGLUTAMINASE ON THE CONSTITUTIVE POLYPEPTIDES OF PEA LEGUMIN

Transglutaminase catalyzes the polymerization of the constitutive polypeptides of legumin. This reaction was studied with the polypeptides in three conformations: organized in the native legumin, dissociated subunits, and separated subunits. In the native globular conformation, only the alpha polypeptides were polymerized, indicating that the beta polypeptides were buried. Among the three types of alpha polypeptides, the two heavy alpha types were more involved in the polymerization reaction than the light type. This lesser reactivity was related to the small amount of Gln accessible and the absence of lysyl residues in the most flexible segments of this polypeptide. The dissociated forms were shown to be better substrates than the native form; however, polymers were obtained with both substrates. When native legumin was used as a substrate, only a few linkages were formed, mainly between the alpha polypeptides. In the case of separated polypeptides, a number of linkages were established between both alpha and beta polypeptides. Dissociation induced by pH did not improve polymerization.