Metabolic Differentiation of Saccharomyces cerevisiae by Ketoconazole Treatment

Abstract Azole fungicides are one of the most wide-spreadantifungal compounds in agriculture and pharmaceutical applications.Their major mode of action is the inhibition of ergosterolbiosynthesis, giving depletion of ergosterol, precursors andabnormal steroids. However, metabolic consequences of suchinhibition, other than steroidal metabolitesare not well established.Comprehensive metabolic profiles of Saccharomyces cerevisiaehas been presented in this study. Wild type yeast was treated eitherwith glucose as control or azole fungicide (ketoconazole). Bothpolar metabolites and lipids were analyzed with gas chromatography-mass spectrometry. Approximately over 180 metabolites werecharacterized, among which 18 of them were accumulated ordepleted by fungicide treatment. Steroid profile gives the mostprominent differences, including the accumulation of lanosteroland the depletion of zymosterol and ergosterol. However, thepolar metabolite profile was also highly different in pesticidetreatment. The concentration of proline and its precursors,glutamate and ornithine were markedly reduced by ketoconazole.Lysine and glycine level was also decreased while the concentrationsof serine and homoserine were increased. The overall metabolicprofile indicates that azole fungicide treatment induces thedepletion of many polar metabolites, which are important in stressresponse.Keywords azole · metabolomics · mode of action · pesticide toxicity · proline · Saccharomyces cerevisiaeIntroductionAzole-type fungicides (e.g., ketoconazole) are widely used inmany agricultural and medicinal applications. Their major modeof action is the inhibition of steroid biosynthesis, being one of themost important primary metabolites in fungal cell membrane(Schwinn, 1984; Zarn et al, 2003). The primary target of thesefungicides is C-14 demethylase, which catalyze the consecutivedemethylation at 14