J. Biol. Chem., Vol. 265, Issue 12, 6713-6725, 04, 1990
Biosynthesis of Fusarium culmorum trichothecenes. The roles of isotrichodermin and 12,13-epoxytrichothec-9-ene [published erratum appears in J Biol Chem 1990 Sep 5;265(25):15347]
LO Zamir, KA Devor, A Nikolakakis and F Sauriol
Centre de Microbiologie Appliquee, Universite du Quebec, Institut Armand-Frappier, Laval, Canada.
Two different approaches enabled us to unambiguously establish the
intermediacy of isotrichodermin and 12,13-epoxytrichothec-9-ene in the
biosynthesis of the trichothecenes 3-acetyldeoxynivalenol and sambucinol,
respectively. The kinetic pulse-labeling method enabled us to detect a
plausible precursor to 3-acetyldeoxynivalenol biosynthesis. Feeding
experiments using the pure 14C-labeled intermediate established that it was
incorporated 27% into 3-acetyldeoxynivalenol but not to sambucinol. The
14C-precursor was subsequently used as a marker to purify the unlabeled
intermediate which was shown to be isotrichodermin by spectroscopic
techniques. In order to trace the enriched carbons incorporated into
3-acetylde-oxynivalenol, specifically deuteriated isotrichodermin was
synthesized and fed to Fusarium culmorum. The 2H NMR spectrum of the
derived 3-acetyldeoxynivalenol proved conclusively the position of the
deuteriums and that isotrichodermin is a major biosynthetic precursor. The
proof that isotrichodermin is converted in vivo to 3-acetyldeoxynivalenol
but not to sambucinol led us to postulate that 12,13-epoxytrichothec-9-ene
might have an important role in the biosynthesis of trichothecenes. We
synthesized 12,13- epoxytrichothec-9-ene with tritium at C-15 or with two
deuteriums at C- 4 and two deuteriums at C-15. These labeled compounds
enabled us to prove that 12,13-epoxytrichothec-9-ene is a major precursor
to sambucinol biosynthesis but is neither converted to isotrichodermin nor
to 3-acetyldeoxynivalenol. We also succeeded in isolating a biosynthetic
intermediate between 12,13-epoxytrichothec-9-ene and sambucinol and
characterized its structure as 3-deoxysambucinol by spectroscopic
techniques (1H NMR, 2H NMR, 13C NMR, correlation spectroscopy,
two-dimensional heteronuclear correlation experiments, and mass
spectroscopy).