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.
Keywords: 1,8-dihydroxynaphthalene-melanin; Black yeast-like fungi; Dothideales; dothideaceous black yeasts; o-diphenoloxidases; p-diphenoloxidases; phenoloxidases
Document Type: Research Article
Publication date: 01 June 2008
- Studies in Mycology is an international journal which publishes systematic monographs of filamentous fungi and yeasts, and special topical issues related to all fields of mycology, biotechnology, ecology, molecular biology, pathology and systematics. The journal is Open-Access and contains monographs or topical issues (5–6 papers per issue). There are no restrictions of length, although it is generally expected that manuscripts should be at least 50 A4 pages in print.
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