Microbial transglutaminase-induced polymerization of β-conglycinin and glycinin in soymilk: A proteomics approach

This study investigated the microbial transglutaminase (MTGase)-induced polymerization of β-conglycinin (7S) and glycinin (11S) in soymilk at 30 °C. SDS-PAGE analysis showed that the 7S acidic proteins, 11S acidic proteins and a portion of the 11S basic proteins were polymerized by MTGase (2.0 units mL−1) during 2 h of incubation. The intensities of the protein bands corresponding to the 7S α′, 7S α, 7S β, and 11S A3 acidic subunits and the 11S basic proteins decreased from 34.4 ± 3.6, 86.8 ± 15.6, 68.4 ± 6.3, 27.3 ± 3.7, 224.9 ± 27.2, and 239.8 ± 26.8 arbitrary units (A.U.) to 7.7 ± 1.5, 3.5 ± 2.7, 13.1 ± 0.9, 3.8 ± 0.7, 15.2 ± 3.5, and 110.0 ± 18.9 A.U., respectively, during that period. Components with higher molecular weights were observed after 2 h of incubation, indicating that inter- or intramolecular crosslinking occurred among the 7S and 11S proteins in the MTGase-treated soymilk. SDS-PAGE and two-dimensional electrophoretic analysis indicated that a portion of the 7S (α′, α, and β), 11S acidic (A1a, A1b, A2, A3, and A4), and 11S basic (B1a, B1b, and B3) proteins in the soymilk were polymerized during incubation with MTGase (1.0 units mL−1). The MTGase-induced polymerization occurred more rapidly for the 7S (α′, α, and β) and 11S acidic (A1a, A1b, A2, A3, and A4) proteins than for the 11S basic (B1a, B1b, and B3) proteins.