Melanization of flavonoids by fungal and bacterial laccases

Laccase activity in plants results in the formation of a number of brown pigments, often referred to as tannins. Laccase-dependent pigment production is also catalogued in numerous fungal and bacterial species. The laccase of the haploid yeast Cryptococcus neoformans forms melanin-like pigmentation...

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Bibliographic Details
Published in:Yeast (Chichester, England) England), 2011-03, Vol.28 (3), p.181-188
Main Authors: Fowler, Zachary L, Baron, Christopher M, Panepinto, John C, Koffas, Mattheos A.G
Format: Article
Language:English
Subjects:
Antimicrobial agents
Bacillus subtilis
Bacillus subtilis - enzymology
Cell walls
Conformation
Cryptococcus neoformans
Cryptococcus neoformans - enzymology
Enzyme Inhibitors - metabolism
Evolution
Flavonoids
Flavonoids - metabolism
Laccase
Laccase - metabolism
Melanins - metabolism
Melanization
Monomers
Pigmentation
Pigments
Polyphenols
Resveratrol
Stilbenes - metabolism
Tannic acid
Virulence
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Summary:Laccase activity in plants results in the formation of a number of brown pigments, often referred to as tannins. Laccase-dependent pigment production is also catalogued in numerous fungal and bacterial species. The laccase of the haploid yeast Cryptococcus neoformans forms melanin-like pigmentation outside the cell wall in the presence of exogenous substrates. While this process is a contributing factor to its virulence in humans, the evolutionary intent for the laccase function remains a mystery. We show here that C. neoformans and Bacillus subtilis have the ability to create melanin-like pigments from a variety of flavonoid molecules across a range of conformations, preferring those with 3′,4′-dihydroxylations. Since flavonoids are ubiquitous plant molecules and often-considered antimicrobial agents, we postulate that they are the intended natural targets of laccase activity and result in the formation of a defensive melanin-like coat. These results suggests a new mechanism by which flavonoid-melanin formation may occur, using not only A- and C-ring linkages, but also monomer links through the B-ring of the flavonoid structure. We also show that resveratrol and other non- and mono-hydroxylated polyphenol substrates have the ability to restrict pigment formation and may be potent inhibitors of laccase activity. Copyright © 2010 John Wiley & Sons, Ltd.
ISSN:0749-503X
1097-0061
1097-0061
DOI:10.1002/yea.1829