Glutathione Levels and γ-Glutamyl Transpeptidase Activities in Aflatoxigenic and Non-Aflatoxigenic Strains of Aspergillus Flavus

Abstract

Glutathione (GSH) levels and activity of the enzyme γ-glutamyl transpeptidase (γ-GT) was assessed in aflatoxigenic and non-aflatoxigenic strains of Aspergillus flavus. The aflatoxigenic strains (NRRL 3240 and NRRL 2999) generally contained enhanced levels of glutathione while it was low in non-aflatoxigenic strains (NRRL 3537 and NRRL 5565) although considerable strain to strain difference existed. In order to examine factors controlling glutathione levels in this organism, all the strains were grown in sucrose low salt (SLS) medium and glucose ammonium nitrate (GAN) medium supporting high and low aflatoxin production respectively. The glutathione level varied for each strain with respect to the medium, suggesting a possible role of media related factors in controlling the formation of glutathione. Aflatoxigenic and non-aflatoxigenic strains were also compared for the activity of γ-GT. Significantly higher activity of γ-GT was associated with aflatoxigenic strains compared to non-aflatoxigenic strains. Factors influencing aflatoxin formation such as growth period and medium, proportionately altered γ-GT activity in the aflatoxigenic strains. These observations point out positive correlation between aflatoxin formation and the inducing effect of endogenous aflatoxin and certain pathways of glutathione metabolism in Aspergillus flavus.