Effects of piperonylic acid on tyrosinase: Mixed-type inhibition kinetics and computational simulations

• Integrating study of enzymology and computational simulations.
• The detailed mechanism of piperonylic acid to affect activity and conformation on tyrosinase.
• The potential usage of piperonylic acid as an alternative to synthetic insecticides via inhibiting tyrosinase.

Piperonylic acid is a natural molecule with a benzoic acid group and high antioxidant capacity. Based on its aromatic acid structure and antioxidant properties, we studied the effects of piperonylic acid on tyrosinase by the analysis of its inhibitory kinetics and computational simulations. Piperonylic acid reversibly inhibited tyrosinase through a mixed-type inhibitory mechanism. The time courses of the tyrosinase inhibition showed that piperonylic acid binds to tyrosinase very quickly and the inactivation processes follow first-order kinetics. The continuous substrate reactions indicated that piperonylic acid induced a tight-binding inhibition and the substrate can promote the inactivation process. The ANS-binding fluorescence of tyrosinase suggested that piperonylic acid did not detectably disrupt the tertiary structure of the enzyme. The results of the computational docking and molecular dynamics simulations showed that piperonylic acid closely interacts with three residues and it might block the active site of tyrosinase.