The chemistry of melanin; mechanism of the oxidation of catechol by tyrosinase.

The accompanying diagram illustrates a mechanism proposed for the enzymic oxidation of catechol (l-5). In the present study the oxidations of catechol and hydroxyhydroquinone at varying concentrations of substrate, enzyme, and hydrogen ion have been followed spectrophotometrically. Step 1, first proposed by Raper on chemical grounds (6), has been confirmed. Further results indicate that the catechol melanin obtained under these conditions is not a polymer of hydroxy-p-quinone.