PMID- 1409448
OWN - NLM
STAT- MEDLINE
DCOM- 19921112
LR  - 20191021
IS  - 0893-5785 (Print)
IS  - 0893-5785 (Linking)
VI  - 5
IP  - 3
DP  - 1992 Sep
TI  - Synthesis and characterization of melanins from dihydroxyindole-2-carboxylic acid 
      and dihydroxyindole.
PG  - 113-21
AB  - Several studies have confirmed that a melanocyte-specific enzyme, dopachrome 
      tautomerase (EC 5.3.2.3), catalyzes the isomerization of dopachrome to 
      5,6-dihydroxyindole-2-carboxylic acid (DHICA) (Pawelek, 1991). Here we report 
      that DHICA, produced either enzymatically with dopachrome tautomerase or through 
      chemical synthesis, spontaneously polymerized to form brown melanin that was 
      soluble in aqueous solutions above pH 5. Under the same reaction conditions, 
      solutions of either DOPA, DOPAchrome, or 5,6-dihydroxyindole (DHI) formed black, 
      insoluble melanin precipitates. When DHICA and DHI were mixed together, with 
      DHICA in molar excess, little or no precipitation of DHI-melanin occurred and the 
      rate and extent of soluble melanin formation was markedly enhanced over that 
      achieved with DHICA alone, suggesting co-polymerization of DHICA and DHI. With or 
      without DHI, DHICA-melanins absorbed throughout the ultraviolet and visible 
      spectra (200-600 nm). The DHICA-melanins precipitated below pH 5, at least in 
      part because of protonation of the carboxyl groups. DHICA-melanins could be 
      passed through 0.22 micron filters but could not be dialyzed through 
      semi-permeable membranes with exclusion limits of 12,000-14,000 daltons. 
      HPLC/molecular sieve analyses revealed apparent molecular weights ranging from 
      20,000 to 200,000 daltons, corresponding to 100-1,000 DHICA monomers per molecule 
      of melanin. DHICA-melanins were stable to boiling, lyophilization, freezing and 
      thawing, and incubation at room temperature for more than 1 year. The natural 
      occurrence of oligomers of DHICA was first reported by Ito and Nichol (1974) in 
      their studies of the brown tapetal pigment in the eye of the sea catfish (Arius 
      felis L.).(ABSTRACT TRUNCATED AT 250 WORDS)
FAU - Orlow, S J
AU  - Orlow SJ
AD  - Department of Dermatology, New York University Medical Center, New York 10016.
FAU - Osber, M P
AU  - Osber MP
FAU - Pawelek, J M
AU  - Pawelek JM
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  - Denmark
TA  - Pigment Cell Res
JT  - Pigment cell research
JID - 8800247
RN  - 0 (Indoles)
RN  - 0 (Melanins)
RN  - 0 (Polymers)
RN  - 4790-08-3 (5,6-dihydroxy-2-indolylcarboxylic acid)
RN  - EC 5.- (Isomerases)
RN  - EC 5.3.- (Intramolecular Oxidoreductases)
RN  - EC 5.3.3.12 (dopachrome isomerase)
RN  - Z3OC8499KG (5,6-dihydroxyindole)
SB  - IM
MH  - Animals
MH  - Humans
MH  - Indoles/*chemistry
MH  - *Intramolecular Oxidoreductases
MH  - Isomerases/chemistry
MH  - Melanins/*chemical synthesis/chemistry
MH  - Mice
MH  - Polymers
MH  - Solubility
MH  - Tumor Cells, Cultured
EDAT- 1992/09/01 00:00
MHDA- 1992/09/01 00:01
CRDT- 1992/09/01 00:00
PHST- 1992/09/01 00:00 [pubmed]
PHST- 1992/09/01 00:01 [medline]
PHST- 1992/09/01 00:00 [entrez]
AID - 10.1111/j.1600-0749.1992.tb00007.x [doi]
PST - ppublish
SO  - Pigment Cell Res. 1992 Sep;5(3):113-21. doi: 10.1111/j.1600-0749.1992.tb00007.x.