ALANINE IS A PRECURSOR IN THE BIOSYNTHESIS OF FUMONISIN B-1 BY FUSARIUM-MONILIFORME

The biosynthesis of fumonisin B-1 by Fusarium moniliforme was studied in liquid culture. Stable isotope labeled alanine was added as a precursor to static and shaken cultures of F. moniliforme. Incorporation of C-13 and H-2 labeled L-alanine into fumonisin B-1 was measured by GC-MS. Under static culture conditions, 20.8 mu g ml(-1) of FB1 were produced with a 5.5% level of incorporation of intact, labeled alanine into fumonisin B-1. Under shake culture conditions, much higher levels of fumonisin B-1 were produced with levels reaching 159-240 mu g 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 B-1 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 B-1.