C-13 labeling indicates that the epoxide-containing amino acid of HC-toxinis biosynthesized by head-to-tail condensation of acetate

HC-toxin, cyclo(D-Prb-L-Ala-D-Ala-L-Aeo), where Aeo stands for 2-amino-9,10 -epoxi-8-oxodecanoic acid, is a potent inhibitor of histone deacetylase. Pr evious molecular genetic studies indicated that HC-toxin biosynthesis requi res a dedicated fatty acid synthase. The incorporation of [C-13]acetate int o HC-toxin was studied using NMR. The pattern of incorporation of C-13 was consistent with the carbons of Aeo being derived from head-to-tail condensa tion of acetate.