Molecular Basis of the Reinforced Effect of Berberine against Cutinase from by Supplying Sodium Stearate as Dispersant.

Berberine (BBR) is a promising botanical pesticide that can reduce the enzyme activity of secreted cutinase from fungal pathogens. However, only less than 15% of total activity was prohibited. Herein we researched BBR's self-aggregation in water via molecular dynamics simulations, and further investigated the effect of dispersant on blocking the aggregation together with the impact on cutinase. Strong hydrophobic interactions were found between adjacent BBR molecules, and these molecules formed clustered conformations at different BBR concentrations. Interestingly, one of the tested dispersants, sodium stearate (ST), is able to insert into BBR clusters and form stable interaction until the end of simulation, resulting in decreased hydrophobic strength in the BBR-ST cluster. More importantly, supply of ST with BBR resulted in BBR's reinforced hydrophobic interactions between BBR and the catalytic center of cutinase, which led to the inactivated mode of cutinase. Finally, wet experiments demonstrated that combined application of BBR and ST indeed resulted in a synergy-like effect on reducing the activity of cutinase. Overall, our findings revealed the mechanism of the reinforced effect of BBR against cutinase when supplying ST as dispersant, suggesting an undiscovered role of ST in enhancing the efficiency of this botanical pesticide.