Peñafiel R, Galindo J D, Solano F, Pedreño E, Iborra J L, Lozano J A
Biochim Biophys Acta. 1984 Aug 14;788(3):327-32. doi: 10.1016/0167-4838(84)90045-1.
The effect of halide ions on frog epidermis tyrosinase has been characterized with the trypsin-activated enzyme. At pH 7, the order of inhibition is I- greater than Br- greater than Cl- greater than F-. Chloride, the most extensively studied halide, shows a competitive pattern with respect to the substrate, L-DOPA. Inhibition is strongly pH-dependent, with a pKa of 6.12 for the responsible protonatable group. Other kinetic constants are also calculated using a novel approach. The mechanism of interaction between chloride and the enzyme is discussed, and a model is proposed in which chloride interferes the tyrosinase activity by displacing a catalytically important ligand, probably a histidine residue of the side-chain, from the copper at the enzyme-active site.
