Very-long-chain fatty acid biosynthesis is inhibited by cafenstrole, N,N-diethyl-3-mesitylsulfonyl-1H-1,2,4-triazole-1-carboxamide and its analogs

The rice herbicide cafenstrole and its analogs inhibited the incorporation of [1-C-14]-oleate and [2-C-14]-malonate into very-long-chain fatty acids ( VLCFAs), using Scenedesmus cells and leek microsomes from Allium porrum. Al though the precise mode of interaction of cafenstrole at the molecular leve l is not completely clarified by the present study, it is concluded that ca fenstrole acts as a specific inhibitor of the microsomal elongase enzyme in volved in the biosynthesis of fatty acids with alkyl chains longer than C-1 8. For a strong VLCFA biosynthesis inhibition an -SO2- linkage of the 1,2,4 -triazole-1-carboxamides was required. Furthermore, NN-dialkyl substitution of the carbamoyl nitrogen and electron-donating groups such as methyl at t he benzene ring of 1,2,4-triazole-1-carboxamides produced a strong inhibiti on of VLCFA formation. A correlation was found between the phytotoxic effec t against barnyardgrass (Echinochloa oryzicola) and impaired VLCFA formatio n.