The Inhibition of Unsaturated Fatty Acid Biosynthesis in Plants by Sterculic Acid

Sterculic acid, 8‐(2‐octyl‐1‐cyclopropenyl)octanoic acid, is a potent inhibitor of the enzyme system converting stearic acid to oleic acid in Chlorella vulgaris. No inhibition of oleic acid for mation from acetate, is, however, observed. With the C 10 , C 12 or C 14 acids as precursor, inhibition increases with chain length. The enzyme system converting oleic acid to linoleic acid is also less sensitive than the stearate‐oleate system. Stearic acid generated internally in leaf preparations anaerobically from acetate is still converted to oleic acid on transference to air in the presence of sterculic acid. Desaturation of added palmitic acid is readily inhibited by sterculic acid, so far as formation of the Δ 7 and Δ 9 acids are concerned. Desaturation of palmitic acid to the 3‐ trans ‐hexadecenoic acid is unaffected by sterculic acid. Two possible schemes to account for the effects of sterculic acid on stearate desaturation are suggested.