4 research outputs found
The influence of ortho- and para-diphenoloxidase substrates on pigment formation in black yeast-like fungi
The influence of ortho- and para-diphenoloxidase substrates on pigment formation in black yeast-like fungi
Dothideaceous black yeast-like fungi (BYF) are known to synthesise
DHN-melanin that is inhibited by the systemic fungicide tricyclazole. The
final step of the DHN melanin pathway is the conjoining of 1,8-DHN molecules
to form the melanin polymer. There are several candidate enzymes for this
step, including phenoloxidases such as tyrosinase and laccases, peroxidases,
and perhaps also catalases. We analysed the type polyphenoloxidases that are
involved in biosynthesis of BYF melanins. For that purpose we used substrates
of o-diphenoloxidases (EC 1.10.3.1.): 4-hydroxyphenyl-pyruvic acid,
L-β-phenyllactic acid, tyrosine, pyrocatechol, 3,4-dihydroxyphenylalanine
and homogentisic acid, as well as substrates of p-diphenoloxidases (EC
1.10.3.2.): syringaldazine, resorcinol, p-phenylenediamine, phloroglucinol,
guaiacol and pyrogallic acid. Fourteen strains of black yeasts originating
from different natural biotopes were investigated. The tested strains could be
divided into four groups based on their ability to produce dark pigments when
cultivated on aromatic substrates of o- and on p-diphenoloxidases. It was
established that syringaldazine, pyrogallic acid and 4-hydrophenyl-pyruvic
acid, β-phenyllactic acid optimally promote melanin biosynthesis. Average
intensity of pigmentation of all strains studied was minimal when guaiacol was
used as a substrate. The present investigation indicates that the melanisation
process may involve more enzymes and more substrates than those commonly
recognised. Black yeasts are likely to contain a multipotent
polyphenoloxidase