Role of mycoferritin from Aspergillus parasiticus (255) in secondary metabolism (aflatoxin production)

Abstract

Aspergillus parasiticus (255), a non-toxigenic isolate showed the presence of secondary metabolites-aflatoxins (B 1, B 2, G 1, G 2) when grown in yeast extract sucrose media but not in basal media, thus demonstrating its toxigenic potential. Native PAGE of the crude protein isolated at different growth periods of A. parasiticus in yeast extract sucrose media containing iron showed prominent expression of mycoferritin from day four onwards. The production of aflatoxins was also maximal on day four, both in the presence and absence of iron. Indicators of oxidative stress metabolites such as reactive oxygen species, thiobarbituric acid reactive species, reduced and oxidized glutathione and antioxidant enzymes like superoxide dismutase and glutathione peroxidase were analyzed both in the presence and absence of iron and the experimental data suggest oxidative stress as a pre-requisite for aflatoxin production. The pro-oxidant role of iron was minimized by induction of mycoferritin and the concomitant alterations in oxidative stress parameters imply an antioxidant role to mycoferritin in secondary metabolism, a finding of significance that has not been reported previously in fungal systems.