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Melanogenesis by tyrosinase action on 3,4‐dihydroxyphenylalanine (DOPA) in the presence of polyethylene glycol: a matrix‐assisted laser desorption/ionization mass spectrometric investigation
Author(s) -
Bertazzo Antonella,
Vogliardi Susanna,
Favretto Donata,
Costa Carlo V. L.,
Allegri Graziella,
Traldi Pietro
Publication year - 2001
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.339
Subject(s) - chemistry , tyrosinase , polyethylene glycol , desorption , peg ratio , matrix assisted laser desorption/ionization , melanin , polymer , mass spectrometry , photochemistry , enzyme , organic chemistry , chromatography , biochemistry , adsorption , finance , economics
The enzymatic reaction between DOPA and tyrosinase, the enzyme considered to be responsible for melanogenesis, was carried out in the presence of polyethylene glycol (PEG). This choice was made in order to increase the solubility of melanins, since these polymers are highly insoluble. The reaction mixtures were sampled at different times, immediately ultrafiltered to remove the enzyme, lyophilized, and analyzed by matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. The results were very different from those obtained in the absence of PEG. Only a few oligomers of dihydroxyindole (DHI) and dihydroxyindole‐2‐carboxylic acid (DHICA) were detected in low abundances, whereas new species originating from reaction of PEG with species belonging to the Raper‐Mason pattern appeared. The results show that, in the presence of PEG, tyrosinase‐catalyzed oligomerization of DOPA exhibits kinetics slower than those observed in the absence of the polymer. However, melanogenesis still takes place in the presence of PEG, as indicated by the formation of black pigments and by the detection of DHI and DHICA oligomers, considered to be the first intermediates in melanin formation. Copyright © 2001 John Wiley & Sons, Ltd.