On the interpretation of tyrosinase inhibition kinetics

Abstract

Tyrosinases (monophenol monooxygenases, EC 1.14.18.1) utilize a reaction mechanism that involves two intertwined catalytic cycles and at least three different ligand-binding enzyme forms. Therefore a variety of different inhibition types may arise in inhibition experiments, depending on the binding mode of the compound studied. Here we discuss a steady-state equation that describes inhibition of the diphenolase cycle of tyrosinase catalysis in a general way. In addition, we employ numerical simulations to explore the kinetic outcome of various binding schemes. As the full equation is far too complex to be applicable for data evaluation by curve fitting, we propose to use the general modifier scheme of Botts-Morales for fitting and demonstrate that especially the value of parameter α of the equation allows conclusions about the binding mode of the inhibitor. The approach is exemplified by selected data describing the inhibition of human tyrosinase by typical inhibitors. © 2014 Informa UK Ltd.