The octadecanoid pathway is a reasonably well-characterized biosynthetic

Biosynthesis

Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...

 pathway for the production of the phytohormone jasmonic acid

Jasmonic acid

Jasmonic acid is derived from the fatty acid linolenic acid. It is a member of the jasmonate class of plant hormones. It is biosynthesized from linolenic acid by the octadecanoid pathway....

 (JA), an important hormone for induction of defense genes. JA is synthesized from alpha-linolenic acid

Alpha-linolenic acid

α-Linolenic acid is an organic compound found in many common vegetable oils. In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid. In physiological literature, it is given the name 18:3 ....

, which can be released from the plasma membrane by certain lipase

Lipase

A lipase is an enzyme that catalyzes the formation or cleavage of fats . Lipases are a subclass of the esterases.Lipases perform essential roles in the digestion, transport and processing of dietary lipids in most, if not all, living organisms...

 enzymes. For example, in the wound defense response, phospholipase C

Phospholipase C

Phosphoinositide phospholipase C is a family of eukaryotic intracellular enzymes that play an important role in signal transduction processes. In general, this enzyme is denoted as Phospholipase C, although three other families of phospholipase C enzymes have been identified in bacteria and in...

 will cause the release of alpha-linolenic acid for JA synthesis.

In the first step, alpha-linolenic acid is oxidized

Redox

Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 by the enzyme lipoxygenase

Lipoxygenase

Lipoxygenases are a family of iron-containing enzymes that catalyse the dioxygenation of polyunsaturated fatty acids in lipids containing a cis,cis-1,4- pentadiene structure. It catalyses the following reaction:...

. This forms 13-hydroperoxylinolenic acid, which is then modified by a dehydrase and undergoes cyclization by allene oxide cyclase to form 12-oxo-phytodienoic acid. This undergoes reduction and three rounds of beta oxidation to form jasmonic acid.