The oxidation of L-Tyrosine to L-DOPA is catalysed by the action of tyrosinase enzymes within the melanocyte's melanosome. In the next step L-DOPA is oxidized to DOPAquinone.
From DOPAquinone, the melanin synthesis pathways diverge to produce either eumelanin or pheomelanin.
Eumelanin: Firstly, DOPAquinone is converted to DOPAchrome through auto-oxidation, and subsequently in the presence of DOPAchrome tautomerase and dihydroxyindole-2-carboxylic acid oxidase, DOPAchrome is converted to 5,6-dihydroxyindole. Finally, the oxidation of 5,6-dihydroxyindole (DHI) to indole-5,6-quinone by tyrosinase leads to the formation of eumelanin (brown-black pigment).
Pheomelanin: In the presence of cysteine or glutathione, dopaquinone is converted to cysteinyl DOPA Subsequently, pheomelanin, a yellow-red pigment, is formed through the oxidative polymerization of cysteinyldopa via 1,4-benzothiazinylalanine intermediates.
From DOPAquinone, the melanin synthesis pathways diverge to produce either eumelanin or pheomelanin.
Eumelanin: Firstly, DOPAquinone is converted to DOPAchrome through auto-oxidation, and subsequently in the presence of DOPAchrome tautomerase and dihydroxyindole-2-carboxylic acid oxidase, DOPAchrome is converted to 5,6-dihydroxyindole. Finally, the oxidation of 5,6-dihydroxyindole (DHI) to indole-5,6-quinone by tyrosinase leads to the formation of eumelanin (brown-black pigment).
Pheomelanin: In the presence of cysteine or glutathione, dopaquinone is converted to cysteinyl DOPA Subsequently, pheomelanin, a yellow-red pigment, is formed through the oxidative polymerization of cysteinyldopa via 1,4-benzothiazinylalanine intermediates.
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