The effect of oxaloacetic acid on tyrosinase activity and structure: Integration of inhibition kinetics with docking simulation.

Oxaloacetic acid (OA) is naturally found in organisms and well known as an intermediate of citric acid cycle producing ATP. We evaluated the effects of OA on tyrosinase activity and structure via integrating methods of enzyme kinetics and computational simulations. OA was found to be a reversible inhibitor of tyrosinase and its induced mechanism was the parabolic non-competitive inhibition type (IC50=17.5±0.5mM and Ki=6.03±1.36mM). Kinetic measurements by real-time interval assay showed that OA induced multi-phasic inactivation process composing with fast (k1) and slow (k2) phases. Spectrofluorimetry studies showed that OA mainly induced regional changes in the active site of tyrosinase accompanying with hydrophobic disruption at high dose. The computational docking simulations further revealed that OA could interact with several residues near the tyrosinase active site pocket such as HIS61, HIS259, HIS263, and VAL283. Our study provides insight into the mechanism by which energy producing intermediate such as OA inhibit tyrosinase and OA is a potential natural anti-pigmentation agent.