Structure-Activity Correlation of Very Long-Chain Fatty Acid Biosynthesis Inhibitors

Abstract

Plant lipid biosynthesis up to fatty acid (C18:0) occurs in plastids. Interference with this fatty acid biosynthesis by herbicidal phenoxy-phenoxy propionic acids or cyclohexanediones is due to the inhibition of acetyl-CoA carboxylase, which explains their herbicidal mechanism of action (Devine et al. 1993). It has been recently concluded that herbicidal chloroacetamides (e.g., alachlor), oxyacetamides (like mefenacet), carbamoylated five-membered nitrogen heterocycles (fentrazamide or cafenstrole), oxiranes (e.g., indanofan) and some miscellaneous compounds (ethofumesate or prosulfocarb) act as specific inhibitors of elongase(s) involved in the extraplastidic biosynthesis of very long-chain fatty acids (VLCFAs) with alkyl chains longer than C₁₈, although the precise mechanism of interaction of the compounds at the molecular level has not been clarified yet (Couderchet et al. 1998; Matthes et al. 1998; Böger et al. 2000; Takahashi et al. 2001a). The relationship between herbicidal action and elongase inhibition by the compounds mentioned above has been discussed in Chapter 6 (Böger and Matthes, Chap. 6, this Vol.). A lack of VLCFAs in the plant cell membranes will lead to death.