The enhancement mechanisms of mucin and lactoferrin on α-amylase activity in saliva: Exploring the interactions using QCM-D and molecular docking

α-Amylase activity differs between individuals and is influenced by dietary behavior and salivary constituents, but limited information is available on the relationship between α-amylase activity and saliva components. This study investigated the impact of salivary proteins on α-amylase activity, their various correlations, the effect of mucin (MUC5B and MUC7) and lactoferrin on the enzymatic kinetics of α-amylase, and the mechanisms of these interactions using the quartz crystal microbalance with dissipation (QCM-D) technique and molecular docking. The results showed that α-amylase activity was significantly correlated with the concentrations of MUC5B (R2 = 0.42, p < 0.05), MUC7 (R2 = 0.35, p < 0.05), and lactoferrin (R2 = 0.35, p < 0.05). An in vitro study demonstrated that α-amylase activity could be significantly increased by mucins and lactoferrin by decreasing the Michaelis constant (Km) of α-amylase. Moreover, the results from the QCM-D and molecule docking suggested that mucin and lactoferrin could interact with α-amylase to form stable α-amylase-mucin and α-amylase-lactoferrin complexes through hydrophobic interactions, electrostatic interactions, Van der Waals forces, and hydrogen bonds. In conclusion, these findings indicated that the salivary α-amylase activity depended not only on the α-amylase content, but also could be enhanced by the interactions of mucin/lactoferrin with α-amylase.