Fig. 1

Fig. 1

Fig. 1. The biosynthesis of eumelanin and pheomelanin in the melanogenesis process. Tyrosinase is the key enzyme involved in the oxidation of tyrosine to dopaquinone while TRYP-1 and TYRP-2 catalyze the final stages of eumelanin formation. The presence of ROS acts as an accelerator to the polymerization of indole units in eumelanogenesis. As for pheomelanogenesis, dopaquinone can react with thiol-containing products like glutathione (GSH) and cysteine to produce both benzothiazine and cysteinyl-dopa, leading to the formation of pheomelanin.