dopachrome

Dopachrome is an intermediate in the biosynthesis of melanin, the pigment responsible for coloration in skin, hair, and eyes. It is produced in melanocytes during the enzymatic oxidation of L-DOPA to dopaquinone by tyrosinase, after which dopaquinone rearranges to form dopachrome.

Dopachrome is a short-lived intermediate that serves as a branching point in eumelanin synthesis. Dopachrome tautomerase (TYRP2) converts it to 5,6-dihydroxyindole-2-carboxylic acid (DHICA), whereas nonenzymatic decarboxylation can yield 5,6-dihydroxyindole (DHI). The subsequent oxidation and polymerization of DHICA and DHI give rise to the mature polymer that constitutes eumelanin. The relative activity of TYRP2 influences the ratio of DHICA- to DHI-derived units in the resulting pigment.

Chemically, dopachrome is relatively unstable and reactive, and it is difficult to isolate in pure form. Its color and instability reflect the transient nature of this stage in the melanogenic pathway.

In research contexts, dopachrome and its related enzymatic steps are used to study tyrosinase activity and melanogenesis. Abnormal regulation of this pathway can be involved in pigmentary disorders and has implications for understanding melanoma biology.