Pulse radiolysis studies of ortho-quinone chemistry relevant to melanogenesis.

2.50
Hdl Handle:
http://hdl.handle.net/10541/85735
Title:
Pulse radiolysis studies of ortho-quinone chemistry relevant to melanogenesis.
Authors:
Land, Edward J; Ramsden, Christopher A; Riley, Patrick A
Abstract:
The 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.
Affiliation:
CRC Drug Development Group, Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Manchester M20 4BX, UK. eland@mighty-micro.co.uk
Citation:
Pulse radiolysis studies of ortho-quinone chemistry relevant to melanogenesis. 2001, 64 (2-3):123-35 J. Photochem. Photobiol. B, Biol.
Journal:
Journal of Photochemistry and Photobiology. B, Biology
Issue Date:
15-Nov-2001
URI:
http://hdl.handle.net/10541/85735
PubMed ID:
11744399
Type:
Article
Language:
en
ISSN:
1011-1344
Appears in Collections:
All Paterson Institute for Cancer Research

Full metadata record

DC FieldValue Language
dc.contributor.authorLand, Edward Jen
dc.contributor.authorRamsden, Christopher Aen
dc.contributor.authorRiley, Patrick Aen
dc.date.accessioned2009-11-10T09:29:32Z-
dc.date.available2009-11-10T09:29:32Z-
dc.date.issued2001-11-15-
dc.identifier.citationPulse radiolysis studies of ortho-quinone chemistry relevant to melanogenesis. 2001, 64 (2-3):123-35 J. Photochem. Photobiol. B, Biol.en
dc.identifier.issn1011-1344-
dc.identifier.pmid11744399-
dc.identifier.urihttp://hdl.handle.net/10541/85735-
dc.description.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.en
dc.language.isoenen
dc.subject.meshBenzoquinones-
dc.subject.meshCatechols-
dc.subject.meshCysteine-
dc.subject.meshCysteinyldopa-
dc.subject.meshDihydroxyphenylalanine-
dc.subject.meshEnzyme Activation-
dc.subject.meshHumans-
dc.subject.meshMelanins-
dc.subject.meshMolecular Structure-
dc.subject.meshMonophenol Monooxygenase-
dc.subject.meshOxidation-Reduction-
dc.subject.meshPhloroglucinol-
dc.subject.meshPulse Radiolysis-
dc.subject.meshQuinones-
dc.titlePulse radiolysis studies of ortho-quinone chemistry relevant to melanogenesis.en
dc.typeArticleen
dc.contributor.departmentCRC Drug Development Group, Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Manchester M20 4BX, UK. eland@mighty-micro.co.uken
dc.identifier.journalJournal of Photochemistry and Photobiology. B, Biologyen

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