PubMed · 4529875
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D T DeVore. 1974. Melanin: visualization and quantification.. https://pubmed.ncbi.nlm.nih.gov/4529875/
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Melanin biosynthesis in the human pathogen Wangiella dermatitidis was inhibited by tricyclazole, causing pentaketide melanin metabolites to accumulate in the cultures. One of these metabolites, scytalone, was racemic and thus different than the (+)-enantiomer from Verticillium dahliae. An albino mutant of W. dermatitidis metabolized scytalone to a pigment ultrastructurally identical to wild-type melanin. Cell-free homogenates of the wild type carried out typical reductive and dehydrative reactions with known melanin intermediates and the reductive reactions were inhibited by tricyclazole. Other reductive and dehydrative reactions that utilize flaviolin and 2-hydroxyjuglone were studied anaerobically with homogenates from both the wild type and the albino mutant. The homogenates converted flaviolin to 5-hydroxyscytalone and products identical to those obtained from 2-hydroxyjuglone. The albino, in culture, carried out the same reactions with 2-hydroxyjuglone but metabolized flaviolin to a number of unknown colored products apparently through oxidative reactions. Similarities between the melanin pathway and the flaviolin and 2-hydroxyjuglone branch pathways are discussed and tricyclazole is shown to inhibit reductive reactions with naphthols in the three pathways.
Melanin synthesis in the dematiaceous, polymorphic hyphomycete Wangiella dermatitidis, a human pathogen, was investigated by biochemical and physiological techniques. Mutants with a decrease or loss in melanin synthesis were induced and isolated. Melanin precursors were obtained from the mutants, purified, and then identified by comparison with authentic compounds from Verticillium dahliae . Isolation of scytalone , vermelone , flaviolin , and 1,8- dihydroxynaphthalene from the mutants of Wangiella dermatitidis, and cross-feeding of the mutants with those of Verticillium dahliae indicated that melanin synthesis in this organism took place by the pentaketide pathway. Melanin that formed in cell walls of an albino mutant treated with scytalone was identified in appearance to that in cell walls of the wild-type strain. This also suggested that pentaketide synthesis of melanin occurred in the fungus.
Melanin synthetized by Pseudomonas aeruginosa has been found to protect these bacteria from hyper- and hypoxia, as well as from the lethal action of ultraviolet radiation. The author believes that melanin-synthetizing P. aeruginosa strains are more dangerous in hospitals than P. aeruginosa strains incapable of synthesizing this pigment.