Human skin pigmentation is caused by melanin synthesis in UV irradiated melanocytes. Tyrosinase
is a key enzyme in melanin synthesis that can catalyze three different reactions: the hydroxylation of
tyrosine to 3,4-dihydroxyphenylalanine (DOPA), the oxidation of DOPA to DOPAquinone and the
oxidation of 5,6-dihydroxyindole (DHI) to indole-quinone [1]. In the absence of thiols, DOPAquinone
changes to DOPAchrome and then to DHI or indole 5,6-quinone 2-carboxylic acid (DHICA). There