PMID- 8908594
OWN - NLM
STAT- MEDLINE
DCOM- 19970121
LR  - 20191024
IS  - 0960-8931 (Print)
IS  - 0960-8931 (Linking)
VI  - 6
IP  - 5
DP  - 1996 Oct
TI  - Hydrogen peroxide generation associated with the oxidations of the eumelanin 
      precursors 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid.
PG  - 341-9
AB  - The ability of iron chelates to promote hydroxyl radical (.OH) formation from 
      hydrogen peroxide (H2O2) via Fenton chemistry was exploited to detect H2O2 
      produced during the oxidations of the eumelanin precursors 5,6-dihydroxyindole 
      (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). H2O2 generation during 
      the autooxidations of DHI and DHICA was confirmed on the basis of the 
      electrochemical detection of three hydroxylation products of salicylate [2,3 and 
      2,5-dihydroxybenzoic acid (DHBA) and catechol], which was used as an .OH 
      indicator. The oxidations of both 5,6-dihydroxyindoles were augmented by 
      tyrosinase and peroxidase without the addition of H2O2. The partial inhibitions 
      by catalase of the auto-oxidations and tyrosinase- and peroxidase-mediated 
      oxidations of DHI and DHICA provide additional evidence of an endogenous origin 
      of H2O2 during the final stages of eumelanogenesis. The mechanism proposed for 
      the formation of H2O2 involves the semiquinones of DHI and DHICA in the univalent 
      transfer of electrons to molecular oxygen. The observations described in this 
      study support previous reports suggesting that factors modulating the levels of 
      H2O2 in melanocytes and melanoma cells play critical roles in directing the 
      course of melanogenesis and influencing the potential cytotoxicity of the 
      biosynthetic pathways.
FAU - Nappi, A J
AU  - Nappi AJ
AD  - Department of Biology, Loyola University of Chicago, IL 60626, USA.
FAU - Vass, E
AU  - Vass E
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, Non-P.H.S.
PL  - England
TA  - Melanoma Res
JT  - Melanoma research
JID - 9109623
RN  - 0 (Enzyme Inhibitors)
RN  - 0 (Indoles)
RN  - 0 (Melanins)
RN  - 0 (Salicylates)
RN  - 12627-86-0 (eumelanin)
RN  - 4790-08-3 (5,6-dihydroxy-2-indolylcarboxylic acid)
RN  - BBX060AN9V (Hydrogen Peroxide)
RN  - E1UOL152H7 (Iron)
RN  - EC 1.11.1.6 (Catalase)
RN  - EC 1.11.1.7 (Peroxidase)
RN  - EC 1.14.18.1 (Monophenol Monooxygenase)
RN  - Z3OC8499KG (5,6-dihydroxyindole)
SB  - IM
MH  - Catalase/chemistry
MH  - Chromatography, High Pressure Liquid
MH  - Enzyme Inhibitors/*chemistry
MH  - Hydrogen Peroxide/*chemical synthesis
MH  - Indoles/*chemistry
MH  - Iron/chemistry
MH  - Kinetics
MH  - Melanins/*chemical synthesis
MH  - Monophenol Monooxygenase/chemistry
MH  - Oxidation-Reduction
MH  - Peroxidase/chemistry
MH  - Salicylates/chemistry
EDAT- 1996/10/01 00:00
MHDA- 1996/10/01 00:01
CRDT- 1996/10/01 00:00
PHST- 1996/10/01 00:00 [pubmed]
PHST- 1996/10/01 00:01 [medline]
PHST- 1996/10/01 00:00 [entrez]
AID - 10.1097/00008390-199610000-00001 [doi]
PST - ppublish
SO  - Melanoma Res. 1996 Oct;6(5):341-9. doi: 10.1097/00008390-199610000-00001.