The inhibitory effect of pyrogallol on tyrosinase activity and structure: Integration study of inhibition kinetics with molecular dynamics simulation

Pyrogallol is naturally found in aquatic plant and has been proposed as a substrate of tyrosinase. In this study, we evaluated the dual effect of pyrogallol on tyrosinase as an inhibitor in the presence of L‑DOPA simultaneously via integrating methods of enzyme kinetics and computational molecular dynamics (MD) simulations. Pyrogallol was found to be a reversible inhibitor of tyrosinase in the presence of L‑DOPA and its induced mechanism was the parabolic non-competitive inhibition type (IC50 = 0.772 ± 0.003 mM and Ki = 0.529 ± 0.022 mM). Kinetic measurements by real-time interval assay showed that pyrogallol induced rapid inactivation process composing with slight activations at the low dose. Spectrofluorimetry studies showed that pyrogallol mainly induced regional changes in the active site of tyrosinase accompanying with hydrophobic disruption at high dose. The computational MD simulations further revealed that pyrogallol could interact with several residues near the tyrosinase active site pocket such as HIS61, HIS85, HIS259, ASN260, HIS263, VAL283, and ALA296. Our study provides insight into the mechanism by which hydroxyl group composing pyrogallol inhibit tyrosinase and pyrogallol is a potential natural anti-pigmentation agent.