A pathway for biosynthesis of divinyl ether fatty acids in green leaves

[1‐ 14 C]α‐Linolenic acid was incubated with a particulate fraction of homogenate of leaves of the meadow buttercup ( Ranunculus acris L.). The main product was a divinyl ether fatty acid, which was identified as 12‐[1′( Z ),3′( Z )‐hexadienyloxy]‐9( Z ), 11( E )‐dodecadienoic acid. Addition of glutathione peroxidase and reduced glutathione to incubations of α‐linolenic acid almost completely suppressed formation of the divinyl ether acid and resulted in the appearance of 13( S )‐hydroxy‐9( Z ), 11( E ), 15( Z )‐octadecatrienoic acid as the main product. This result, together with the finding that 13( S )‐hydroperoxy‐9( Z ), 11( E ), 15( Z )‐octadecatrienoic acid served as an efficient precursor of the divinyl ether fatty acid, indicated that divinyl ether biosynthesis in leaves of R. acris occurred by a two‐step pathway involving an ω6‐lipoxygenase and a divinyl ether synthase. Incubations of isomeric hydroperoxides derived from α‐linolenic and linoleic acids with the enzyme preparation from R. acris showed that 13( S )‐hydroperoxy‐9( Z ), 11( E )‐octadecadienoic acid was transformed into the divinyl ether 12‐[1′( Z )‐hexenyloxy]‐9( Z ), 11( E )‐dodecadienoic acid. In contrast, neither the 9( S )‐hydroperoxides of linoleic or α‐linolenic acids nor the 13( R )‐hydroperoxide of α‐linolenic acid served as precursors of divinyl ethers.