Dopaquinone (DQ)

Dopaquinone is a highly reactive ortho-quinone intermediate generated during the rate-limiting steps of melanogenesis. It is produced by the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) by the enzyme tyrosinase (EC 1.14.18.1) [PubChem CID 160505]. As a potent electrophile, dopaquinone serves as a pivotal branch point in melanin synthesis; it can spontaneously cyclize to form dopachrome, leading to eumelanin, or react with thiol-containing compounds like glutathione and cysteine to produce cysteinyldopas, leading to pheomelanin [PMID: 17417017]. In pathological states, the high reactivity of dopaquinone contributes to cellular damage. In melanoma, it is a precursor to pigment-related oxidative stress, while in Parkinson's disease, its formation from dopamine oxidation is linked to the degeneration of dopaminergic neurons through protein adduct formation and mitochondrial dysfunction [PMID: 15183511]. Although dopaquinone is a metabolite rather than a protein target, it is central to the development of tyrosinase inhibitors and antioxidant therapies designed to mitigate its cytotoxic effects. Monitoring levels of its derivatives, such as 5-S-cysteinyldopa, serves as a biomarker for melanoma progression and therapeutic efficacy [PMID: 24555142].

Other names

o-DopaquinoneL-Dopaquinone2-amino-3-(3,4-dioxocyclohexa-1,5-dien-1-yl)propanoic acid

Dopaquinone is a reactive metabolic intermediate; therapeutic intervention typically involves scavenging the molecule with antioxidants or inhibiting the upstream enzyme tyrosinase to prevent its synthesis.