Regulation and metabolic background of polyketide formation. I. Effects of (-)-hydroxycitrate and metabolic roles of citrate and malate in fatty acid and polyketide formations.

The effects of (-)-hydroxycitrate on fatty acid and alternariol syntheses from glucose and acetate in Alternaria alternata were investigated. Fatty acid synthesis from glucose and acetate was inhibited by (-)-hydroxycitrate. The inhibition could partly be removed by the addition of malate or isocitrate. Alternariol synthesis from glucose was also inhibited by (-)-hydroxycitrate. This inhibition was not influenced to the same extent by malate addition as was that of fatty acid synthesis. It is shown that ATP -citrate lyase is essential not only for the production of cytoplasmic acetyl-CoA but also for the production of NADPH by supplying malate via oxaloacetate.