Pigmentation in dogs and other mammals (including you) is caused by the relative amounts and types of two classes of pigment: eumelanin and phaeomelanin. The eumelanins are the black and brown pigments, and the phaeomelanins are red and yellow. Both eumelanins and phaeomelanins are synthesized in pigment-producing cells called melanocytes. First, the enzyme tyrosinase converts the amino acid tyrosine to a chemical called dopaquinone. If the enzyme called tyrosinase-related protein 2 (TRP-2) is present, it converts the dopaquinone to a version of eumelanin that has a brown color, Cocoa's pigment. If the enzyme called tyrosinase-related protein 1 (TRP-1) is present, it converts the brown version of eumelanin into the final, black pigment.
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