Kinetic characterisation of the reaction mechanism of mushroom tyrosinase on tyramine/dopamine and L-tyrosine methyl esther/L-dopa methyl esther.

Tyrosinase or polyphenol oxidase is the key enzyme in melanin biosynthesis and for the enzymatic browning of fruits and vegetables. Our research group previously proposed a kinetic reaction mechanism for tyrosinase acting on some phenolic substrates, whose reliability was demonstrated for tyrosinases from several fruits and vegetables. A kinetic analysis and an experimental design for testing the reliability of the kinetic reaction mechanism of tyrosinase are reported. The applicability of the mechanism to the oxidation of tyramine/dopamine and L-tyrosine methyl esther/L-dopa methyl esther has been checked. Some structure/activity topics are discussed. A complete kinetic characterisation of the oxidation of these phenolic substrates has been made. This will be useful for further studies about the control of depigmenting agents, antimelanome drugs and antibrowning reagents acting on tyrosinase.