Alanine is a precursor in the biosynthesis of fumonisin B₁ byFusarium moniliforme

Abstract

The biosynthesis of fumonisin B₁ byFusarium moniliforme was studied in liquid culture. Stable isotope labeled alanine was added as a precursor to static and shaken cultures ofF. moniliforme. Incorporation of¹³C and²H labeled L-alanine into fumonisin B₁ was measured by GC-MS. Under static culture conditions, 20.8 µg ml⁻¹ of FB₁ were produced with a 5.5% level of incorporation of intact, labeled alanine into fumonisin B₁. Under shake culture conditions, much higher levels of fumonisin B₁ were produced with levels reaching 159–240 µg ml⁻¹ by 21 days after culture initiation. A lower level of alanine incorporation, from 1.1–1.4%, was observed under these conditions. Under shake conditions, incorporation of labeled alanine was reduced because of the rapid metabolism of these cultures combined with the high level of fumonisin B₁ production resulted in rapid turnover of the added, labeled alanine and reduced percentage of incorporation. The evidence presented indicates that alanine is incorporated intact into fumonisin B₁.