Kinetic properties of light-dependent ascorbic acid oxidation by melanin

Randolph D. Glickman, Raymond Sowell, Kwok Wai Lam

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


The kinetic properties of ascorbic acid oxidation by light-activated melanin granules demonstrate the presence of a specific reactive site on the melanin granule saturable by ascorbic acid. Increased light intensity increased the Vmax and reduced the Km of this reaction, indicating increased affinity of the active site for ascorbic acid. The kinetics of this reaction are not markedly changed in a reduced-oxygen environment. Ascorbic acid oxidation is competitively inhibited by isoascorbic acid, an epimer of ascorbic acid, while other tested reducing agents are inactive. The Ki for isoascorbic acid is 1 mM, about the same as the Km of ascorbic acid.

Original languageEnglish (US)
Pages (from-to)453-457
Number of pages5
JournalFree Radical Biology and Medicine
Issue number4
StatePublished - Oct 1993


  • Ascorbic acid
  • Free radicals
  • Isoascorbic acid
  • Kinetics
  • Light
  • Melanin

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)


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