Synthesis of Melanin

Introduction:

• Melanin is produced by the oxidation of the amino acid  tyrosine, followed by polymerization.
• The melanin pigments are produced in a specialized group of cells known as melanocytes.

There are three basic types of melanin: eumelanin, pheomelanin, and neuromelanin. The most common type is eumelanin.

• Pheomelanin is a cysteine-derivative that contains polybenzothiazine portions that are largely responsible for the color of red hair.
• Neuromelanin is found in the brain, though its function remains obscure.

• Melanin is derived from tyrosine, and more directly from DOPA.
• Differently from tyrosine hydroxylase, tyrosinase, a copper enzyme, uses molecular oxygen directly to form DOPA from tyrosine.
• The synthesis of melanin occurs in the melanocyte, and the reactions starting with tyrosine.
• After the formation of DOPA from tyrosine, the further conversion of DOPA to DOPAquinone follows. 
• Number of intermediates are formed ending in  indolequinone that polymerizes to form melanin.
• The more common product is eumelanin (brown) but in the presence of cysteine.
• Pheomelanin can be formed (red to yellow). 
• Absence of melanin causes Albinism.

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