Abstract
Aflastatin A (AsA) and blasticidin A (BcA), metabolites of Streptomyces with similar structures, are inhibitors of aflatoxin production by Aspergillus parasiticus and they can inhibit production of other fungal polyketide metabolites such as melanin produced by Colletotrichum lagenarium. We have clarified that they inhibit a very early step involved in aflatoxin and melanin production, which may be present in primary metabolism of the fungi. In this study, to elucidate the mode of action of AsA and BcA, we examined their effects on pH control and carbon metabolism in A. parasiticus. As a result, they did not affect pH of culture broth and phosphatase expression pattern in the mycelia, but they drastically changed carbon metabolism in the fungus by elevating glucose consumption and ethanol accumulation. We also prepared a photoaffinity probe of BcA to identify its target molecule. A specific binding protein of the probe has not been obtained, but we found that biotinylated proteins endogenously present in the fungus became undetectable when BcA was added to the culture. This suggested that BcA affected metabolism of biotinylated proteins of the fungus.
