PMID- 24807014
OWN - NLM
STAT- MEDLINE
DCOM- 20160516
LR  - 20140901
IS  - 1755-148X (Electronic)
IS  - 1755-1471 (Linking)
VI  - 27
IP  - 5
DP  - 2014 Sep
TI  - Effect of pH on elementary steps of dopachrome conversion from first-principles 
      calculation.
PG  - 734-43
LID - 10.1111/pcmr.12256 [doi]
AB  - Dopachrome conversion, in which dopachrome is converted into 5,6-dihydroxyindole 
      (DHI) or 5,6-dihydroxyindole-2-carboxylic acid (DHICA) upstream of 
      eumelanogenesis, is a key step in determining the DHI/DHICA monomer ratio in 
      eumelanin, which affects the antioxidant activity. Although the ratio of 
      DHI/DHICA formed and the conversion rate can be regulated depending on pH, the 
      mechanism is still unclear. To clarify the mechanism, we carried out 
      first-principles calculations. The results showed the kinetic preference of 
      proton rearrangement to form quinone methide intermediate via beta-deprotonation. We 
      also identified possible pathways to DHI/DHICA from the quinone methide. The DHI 
      formation can be achieved by spontaneous decarboxylation after proton 
      rearrangement from carboxyl group to 6-oxygen. alpha-Deprotonation, which leads to 
      DHICA formation, can also proceed with a significantly reduced activation barrier 
      compared with that of the initial dopachrome. Considering the rate of the proton 
      rearrangements in a given pH, we conclude that the conversion is suppressed at 
      acidic pH.
CI  - (c) 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
FAU - Kishida, Ryo
AU  - Kishida R
AD  - Department of Applied Physics, Osaka University, Suita, Osaka, Japan.
FAU - Ushijima, Yohei
AU  - Ushijima Y
FAU - Saputro, Adhitya G
AU  - Saputro AG
FAU - Kasai, Hideaki
AU  - Kasai H
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20140606
PL  - England
TA  - Pigment Cell Melanoma Res
JT  - Pigment cell & melanoma research
JID - 101318927
RN  - 0 (Indolequinones)
RN  - 0 (Indoles)
RN  - 0 (Protons)
RN  - 0 (Solvents)
RN  - 138230-21-4 (quinone methide)
RN  - 3571-34-4 (dopachrome)
RN  - 4790-08-3 (5,6-dihydroxy-2-indolylcarboxylic acid)
RN  - 7YNJ3PO35Z (Hydrogen)
RN  - EC 5.3.- (Intramolecular Oxidoreductases)
RN  - Z3OC8499KG (5,6-dihydroxyindole)
SB  - IM
MH  - Humans
MH  - Hydrogen/chemistry
MH  - Hydrogen-Ion Concentration
MH  - Indolequinones/*chemistry
MH  - Indoles/chemistry
MH  - Intramolecular Oxidoreductases/metabolism
MH  - Kinetics
MH  - Models, Chemical
MH  - Pigmentation
MH  - Protons
MH  - Software
MH  - Solvents/chemistry
OTO - NOTNLM
OT  - DHI
OT  - DHICA
OT  - dopachrome
OT  - eumelanin
OT  - first-principles calculation
OT  - pH effect
EDAT- 2014/05/09 06:00
MHDA- 2016/05/18 06:00
CRDT- 2014/05/09 06:00
PHST- 2014/03/11 00:00 [received]
PHST- 2014/05/01 00:00 [accepted]
PHST- 2014/05/09 06:00 [entrez]
PHST- 2014/05/09 06:00 [pubmed]
PHST- 2016/05/18 06:00 [medline]
AID - 10.1111/pcmr.12256 [doi]
PST - ppublish
SO  - Pigment Cell Melanoma Res. 2014 Sep;27(5):734-43. doi: 10.1111/pcmr.12256. Epub 
      2014 Jun 6.