Pulse radiolysis studies of ortho-quinone chemistry relevant to melanogenesis.
AffiliationCRC Drug Development Group, Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Manchester M20 4BX, UK. email@example.com
MetadataShow full item record
AbstractThe contributions of pulse radiolysis towards characterisation of unstable ortho-quinones relevant to melanogenesis are reviewed. The quinones discussed include dopaquinone, the precursor of both eumelanogenesis and phaeomelanogenesis, and 5-S-cysteinyldopaquinone, an early component of the phaeomelanogenic pathway. Redox exchange between dopaquinone and 5-S-cysteinyldopa is shown to be a determinant of the balance between eumelanogenesis and phaeomelanogenesis. Ortho-quinones resulting from the oxidation of tertiary N,N-dialkylcatecholamines cyclise to redox-inactive betaines which fail to autoactivate tyrosinase. This is consistent with the dopa detected during melanogenesis catalysed by tyrosinase being formed indirectly by a combination of dopaquinone intramolecular reductive addition to form leucodopachrome (cyclodopa), followed by redox exchange between remaining dopaquinone and leucodopachrome. Rapid tautomerism of the ortho-quinone of 4-cyanomethylcatechol to a redox-inactive quinomethane likewise inhibits tyrosinase autoactivation. The incorporation of trihydric phenol moieties in melanin is modelled by the reactions of several ortho-quinones with phloroglucinol, which itself is not directly oxidised by tyrosinase due to the meta-positioning of the hydroxyl groups. The importance of a susceptibility towards nucleophilic attack as well as a propensity to undergo redox-exchange, in the chemistry of melanogenic ortho-quinones, is emphasised.
CitationPulse radiolysis studies of ortho-quinone chemistry relevant to melanogenesis. 2001, 64 (2-3):123-35 J. Photochem. Photobiol. B, Biol.
JournalJournal of Photochemistry and Photobiology. B, Biology
- Spontaneous redox reactions of dopaquinone and the balance between the eumelanic and phaeomelanic pathways.
- Authors: Land EJ, Riley PA
- Issue date: 2000 Aug
- Chemistry of mixed melanogenesis--pivotal roles of dopaquinone.
- Authors: Ito S, Wakamatsu K
- Issue date: 2008 May-Jun
- Tyrosinase autoactivation and the chemistry of ortho-quinone amines.
- Authors: Land EJ, Ramsden CA, Riley PA
- Issue date: 2003 May
- Mechanistic studies of catechol generation from secondary quinone amines relevant to indole formation and tyrosinase activation.
- Authors: Land EJ, Ramsden CA, Riley PA, Yoganathan G
- Issue date: 2003 Aug
- A pulse radiolysis investigation of the oxidation of the melanin precursors 3,4-dihydroxyphenylalanine (dopa) and the cysteinyldopas.
- Authors: Thompson A, Land EJ, Chedekel MR, Subbarao KV, Truscott TG
- Issue date: 1985 Nov 22