BIOSYNTHESIS OF THE TRICHOTHECENE 3-ACETYLDEOXYNIVALENOL - CELL-FREE HYDROXYLATIONS OF ISOTRICHODERMIN

3-Acetyldeoxynivalenol is the major trichothecene produced by the fung us Fusarium culmorum. Studies in vivo with F. culmorum have establishe d the following biosynthetic precursors of 3-acetyldeoxynivalenol: iso trichool --> isotrichodiol --> isotrichodermin --> 15-deacetylcalonect rin, 7 alpha-hydroxyisotrichodermin, 8 alpha-hydroxyisotrichodermin -- > calonectrin --> deoxynivalenol. In this paper, we describe in vitro investigations of one of these metabolic steps. The cell-free system o f F. culmorum that converts isotrichodermin into 15-deacetylcalonectri n, 7 alpha-hydroxyisotrichodermin, and 8 alpha-hydroxyisotrichodermin is described here. This preparation requires NADPH but not NADH for ac tivity and is not inhibited by carbon monoxide, cyanide, or known oxyg enase inhibitors, such as SKF-525-A or ancymidol.