alpha-Linolenic acid is a poly-unsaturated fatty acid with an 18-carbon chain and three cis double bonds. Its primary role in Arabidopsis thaliana is in being a precursor of the phytohormone jasmonic acid. Being a precursor for jasmonic acid, it plays a role in gene responses to feeding from insects. It is also a precursor to other molecules involved in defense signalling such as cis-3-hexenyl acetate. alpha-Linolenic acid itself modulates gene transcription in response to hyperosmotic salinity, heat acclimation, and oxidative stress. alpha-Linolenic acid is released from the hydrolysis of a phosphatidylcholine membrane lipid. It then has a hydroperoxy group added by a dioxygenase in either the 2, 9, or 13 position to form 2(R)-HPOT, 9(S)-HPOT, or 13(S)-HPOT respectively. The oxidation of alpha-linolenic acid to 13(S)-HPOT is the first step in the jasmonic acid synthesis and leads to that separate pathway. 2(R)-HPOT is formed in an oil body and undergoes a spontaneous decarboxylation to form a heptadecatrienal. 9(S)-HPOT, or 13(S)-HPOT are both formed in a chloroplast and cleaved by probable inactive linolenate hydroperoxide lyase to form an aldehyde and an oxo-carboxylic acid. The hexenal from 13(S)-HPOT is reduced by alcohol dehydrogenase class-P to form a hexenol, which undergoes an esterification with acetyl-CoA to form 3-hexenyl acetate.

alpha-Linolenic Acid Metabolism References