ASPERGILLUS HAS DISTINCT FATTY-ACID SYNTHASES FOR PRIMARY AND SECONDARY METABOLISM

Aspergillus nidulans contains two functionally distinct fatty acid syn thases (FASs): one required for primary fatty acid metabolism (FAS) an d the other required for secondary metabolism (sFAS). FAS mutants requ ire long-chain fatty acids for growth, whereas sFAS mutants grow norma lly but cannot synthesize sterigmatocystin (ST), a carcinogenic second ary metabolite structurally and biosynthetically related to aflatoxin. sFAS mutants regain the ability to synthesize ST when provided with h exanoic acid, supporting the model that the ST polyketide synthase use s this short-chain fatty acid as a starter unit, The characterization of both the polyketide synthase and FAS may provide novel means for mo difying secondary metabolites.