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Abstract No.: TuP-004
Session: Biomolecular Assemblies
Presentation date: Tue, Aug 29, 2006
Presentation time: 14:30 – 16:00

An Investigation Based on MALDI/MS on the Possible Role of Tryptophan and 7-hydroxytryptophan in Melanogenesis

Antonella Bertazzo1, Anna Smaniotto2, Stefano Comai1, Carlo V. L. Costa1, Graziella Allegri1, Pietro Traldi2

1 University of Padova, Padova, Italy
2 CNR, ISTM, Padova, Italy

Correspondence address: Antonella Bertazzo, University of Padova, Pharmaceutical Sciences, Via Marzolo 5, Padova, 35131 Italy.

Keywords: Acids, Amino; MALDI; Natural Products; Oligomers.

Novel aspect: The present MALDI/MS investigation allows to establish the possible role of 7-hydroxytryptophan in melanin biosynthesis.

 

The activity of tyrosinase and peroxidase + H2O2 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 mainly due to reaction of anthranilic acid (AA) and TRP. However, looking at UV and fluorescence data, the oligomers cannot belong to the melanin pattern, but their possible role in melanogenesis is not to be excluded. Instead 7-hydroxytryptophan leads, once reacted with the two enzymes, to dark brown products, indicating its possible role in melanin production. On the contrary of what 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 deeply different behaviour of 7-HTP. In fact, in the case of 5-hydroxytryptophan, a oligomerization takes place through the formation of 5-hydroxytryptamine and 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 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 + H2O2.