The possible role of some enzymes in sclerotia formation in Aspergillus ochraceus

Abstract

The role of some enzymes in sclerotia production by Aspergillus ochraceus was studied using a sclerotia-producing strain grown under conditions in which sclerotia production was either favoured or inhibited. In addition, a mutant strain incapable of producing sclerotia was used. No significant differences in patterns of soluble proteins, polyphenol oxidase, and esterases could be detected electrophoretically by gel electrophoresis, while the peroxidase pattern of both the sclerotia-producing strain and the mutant showed three bands as compared with two bands that appeared when sclerotia formation was inhibited. The activities of the tricarboxylic acid cycle enzymes, malate dehydrogenase and succinate dehydrogenase, and those of the pentose-phosphate pathway, glucose-6 phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, were almost identical in sclerotia- and nonsclerotia-producing mycelia. The activities of isocitrate lyase and malate synthetase, key enzymes of the glyoxylate cycle, and that of glyoxylate dehydrogenase which is related to this cycle were significantly reduced when sclerotia formation was inhibited either by methionine or by high levels of CO2. It is suggested that the glyoxylate cycle plays an important role in sclerotia formation in the fungus.