Melanin is the term used for multiple pigments found in many organisms, and specifically our skin, hair and iris tissues. There are three types of melanin, eumelanin, pheomelanin and neuromelanin. Eumelanin is the most common, and can be brown or black. Melanin is produced by melanocytes, and is a polymer made of smaller components, so there are many types with different polymerization patterns and proportions of components. To begin, this pathway takes L-dopachrome from the L-dopa and L-dopachrome biosynthesis pathways and, in the melanosome, it can either spontaneously form 5,6-dihydroxyindole, or can form 5,6-dihydroxyindole-2-carboxylic acid using L-dopachrome tautomerase as the catalyst. Both 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid use tyrosinase as a catalyst to form indole-5,6-quinone and indole-5,6-quinone-2-carboxylate respectively. Finally, some combination of 5,6-hydroxyindole, indole-5,6-quinone, 5,6-dihydroxyindole-2-carboxylic acid and indole-5,6-quinone-2-carboxylate combine to form melanochrome, an intermediate in the formation of eumelanin, and finally forms eumelanin, the final product of this pathway.

Eumelanin Biosynthesis References