Enzymatic oligomerization of tyrosine by tyrosinase and peroxidase studied by matrix-assisted laser desorption/ionization mass spectrometry

✍ Scribed by Antonella Bertazzo; Carlo V.L. Costa; Graziella Allegri; Marta Schiavolin; Donata Favretto; Pietro Traldi

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 86 KB
• Volume: 13
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(19990330)13:6<542::aid-rcm521>3.0.co;2-h

✦ Synopsis

The role of tyrosinase in melanogenesis starting from tyrosine, considered the physiological melanin precursor, was compared with that of peroxidase /H 2 O 2 by matrix-assisted laser desorption/ionization mass spectrometry. Samples were prepared by ultrafiltering the tyrosine-enzyme solution at various reaction times, and were then immediately lyophilized. In parallel, samples obtained by the action of peroxidase or H 2 O 2 alone were analyzed and compared. Samples originating from the action of tyrosinase on tyrosine revealed the presence of oligomers of 5,6-dihydroxyindole (DHI), 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and DHI-DHICA, and their molecular masses increased with increasing reaction times up to octamer levels. When the reaction was carried out in the presence of the peroxidase/H 2 O 2 system, a completely different oligomeric pattern was revealed in the ultrafiltered samples. In fact, the species detected at various times were not due to DHI oligomers, but showed a tyrosine-based skeleton.