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Inactivation of Soybean Bowman–Birk Inhibitor by Stevioside: Interaction Studies and Application to Soymilk
- Liu, Chun, Luo, Lijuan, Wu, Ying, Yang, Xiaoquan, Dong, Jie, Luo, Feijun, Zou, Yuan, Shen, Yingbin, Lin, Qinlu
- Journal of agricultural and food chemistry 2019 v.67 no.8 pp. 2255-2264
- Bowman-Birk inhibitor, computer simulation, hydrogen bonding, moieties, sensory properties, soybeans, soymilk, stevioside, sucrose, trypsin
- In this work, the interaction of the soybean Bowman–Birk inhibitor (BBI) with stevioside (STE) was studied by stopped-flow–fluorescence and molecular docking. STE’s inactivation of protease-inhibitor activities in soymilk and the influence of STE addition on the sensory character of soymilk were also evaluated. The results indicate that STE binds BBI with a binding constant (Kₐ) of 3.38 × 10⁵ L mol–¹ to form a 1:1 complex. The docking study reveals that two hydrogen bonds are formed between the side-chain of Lys16 (reactive site 1) of BBI and the glucose-ring hydroxyl groups of STE, which may block BBI from contacting trypsin and thus deactivate the trypsin-inhibitor activity (TIA) of BBI. Moreover, the residual TIA in soymilk could also be inactivated by STE. A mixture of 159 mg/L STE and 60 g/L sucrose could be used for sweetening soymilk without affecting the sensory characteristics when compared to a reference product sweetened with 9% sucrose.