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A mass spectrometric investigation on the possible role of tryptophan and 7‐hydroxytryptophan in melanogenesis
Author(s) -
Smaniotto Anna,
Comai Stefano,
Bertazzo Antonella,
Costa Carlo V. L.,
Allegri Graziella,
Seraglia Roberta,
Traldi Pietro
Publication year - 2006
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.1051
Subject(s) - chemistry , 5 hydroxytryptophan , tyrosinase , anthranilic acid , tryptophan , melanin , tryptophan hydroxylase , peroxidase , fluorescence , serotonin , stereochemistry , organic chemistry , enzyme , biochemistry , amino acid , serotonergic , physics , receptor , quantum mechanics
The activity of tyrosinase and peroxidase + H 2 O 2 in promoting melanogenesis from tryptophan (Trp) and 7‐hydroxytryptophan (7‐HTP) has been investigated. The reaction samples have been drawn at different reaction times and analysed by MALDI mass spectrometry. The data obtained showed that tryptophan undergoes, under tyrosinase and peroxidase action, an oligomerization process mainly due to the reaction of anthranilic acid (AA) and Trp. However, analysing the UV and fluorescence data, it is seen that the oligomers cannot belong to the melanin pattern, but their possible role in melanogenesis is not to be excluded. Once it reacts with the two enzymes, 7‐hydroxytryptophan leads to dark brown products, indicating its possible role in melanin production. In contrast to what was observed in the case of 5‐hydroxytryptophan, for which oligomers were constituted by 5‐hydroxytryptophan (5‐HTP) and 5‐hydroxytryptamine (5‐HT) units, the MALDI data indicate a sharply different behaviour for 7‐HTP. In fact, in the case of 5‐hydroxytryptophan, oligomerization takes place through the formation of 5‐hydroxytryptamine and the oligomerization products are due to mixed 5‐HTP—5‐HT oligomers. In the case of 7‐hydroxytryptophan, the formation of 7‐hydroxytryptamine (7‐HT) is also observed, but it does not seem to play any role; the only oligomerization products formed are due to the reaction of 7‐hydroxytryptophan and AA. The data so obtained indicate that 7‐hydroxytryptophan acts like an effective melanin precursor in the presence of both tyrosinase and peroxidase + H 2 O 2 . Copyright © 2006 John Wiley & Sons, Ltd.