Affordable Access

Publisher Website

Peroxidase as an alternative to tyrosinase in the oxidative polymerization of 5,6-dihydroxyindoles to melanin(s)

Authors
Journal
Biochimica et Biophysica Acta (BBA) - General Subjects
0304-4165
Publisher
Elsevier
Publication Date
Volume
1073
Issue
2
Identifiers
DOI: 10.1016/0304-4165(91)90152-7
Keywords
  • Melanogenesis
  • Tyrosinase
  • Peroxidase
  • 5
  • 6-Dihydroxyindole
  • 5
  • 6-Dihydroxyindole Oligomer
Disciplines
  • Biology

Abstract

Abstract The ability of the peroxidase/H 2O 2 system to promote the oxidative polymerization of 5,6-dihydroxyindole (DI) and 5,6-dihydroxyindole-2-car☐ylic acid (DICA) to melanin pigments was investigated in comparison with tyrosinase, commonly regarded as the sole enzyme involved in melanogenesis. In 0.025 M phosphate buffer at pH 6.8, tyrosinase (2.7·10 −3 U/ml) induced a smooth oxidation of 3.0·10 −5 M DI (initial rate = 4.4·10 −5M/s) to give a complex mixture of products with the 2,4′-dimer I as the main component, whereas, under the same conditions, peroxidase (0.44 U/ml) and 1.2·10 −4 M H 2O 2 caused the instantaneous conversion of the substrate to a well-defined pattern of products, comprising the 2,4′-and 2,7′-DI dimers I and II, and the related trimers III and IV. When 3.0·10 −5 M DICA was used as the substrate, the difference in the effectiveness of the enzymes was much more pronounced. Thus, while peroxidase accomplished the fast oxidation of the indole, yielding the dimer V and the trimer VI as the main products, tyrosinase proved unable to induce more than a poor and sluggish reaction with an initial rate of 5.6·10 −6 M/s. These results raise the possibility that peroxidase, rather than, or in addition to, tyrosinase, may play a critical role in the later stages of the biosynthesis of melanins.

There are no comments yet on this publication. Be the first to share your thoughts.