The enzymic conversion of linoleic acid into 9-(nona-1′,3′-dienoxy)non-8-enoic acid, a novel unsaturated ether derivative isolated from homogenates of Solanum tuberosum tubers

Abstract

1. A major component of the lipids in aqueous (pH7.5) homogenates of tuber tissue from Solanum tuberosum was isolated and characterized as 9-(nona-1',3'-dienoxy)non-8-enoic acid. 2. This novel unsaturated ether fatty acid derivative, which contains a butadienylvinyl ether function, has the structure: [Formula: see text] and is formed from linoleic acid by a sequence of enzymic reactions. 3. A precursor of the unsaturated ether derivative is 9-d-hydroperoxyoctadeca-10,12-dienoic acid, formed by the action of S. tuberosum lipoxygenase on linoleic acid. 4. An enzyme that converts the fatty acid hydroperoxide into the unsaturated ether derivative was isolated from S. tuberosum. The pH optimum of this enzyme is approx. 9, although the overall conversion of linoleic acid into the ether derivative is maximal at pH7.5. 5. An unusual feature of this pathway is the insertion of an oxygen atom into the alkyl chain of a fatty acid. 6. This novel mechanism may play a role in the breakdown of polyunsaturated fatty acids to volatile products in plants.

Lipid metabolism in arbuscular mycorrhizal roots of Medicago truncatula

“…This feature distinguishes this enzyme from other c loned DES enzymes from Solanaceae species. The conversion of LA into the divinyl ether CA was first reported in the early 1970s by Galliard and co-workers [20]. Related activities leading to formation of EA and EnA are known from garlic and different Ranunculaceae species and a number of algae [9][10][11].…”

“…The fixation was performed at 4 °C for 12 h. After three washes for 20 min each in PBS the specimens were dehydrated in a graded ethanol series (20, 30, 40, 50, 60, 70, 90, 97, 100 % ethanol), each step for 40 min. Embedding in Steedman's wax (Vitha et al, 1997) was done first for 1 h in 100 % ethanol, then in a graded wax/ethanol series (10,20,35,50,65, and 80 % v/v wax) at 37 -40 °C followed by three changes of pure wax, each for 1 -2 h. Ribbons of 8 µm thick sections were placed on silanized slides coated with egg white and stretched by addition of a small drop of distilled water to one end of the ribbon. The excess water was soaked away from the opposite end of the ribbon by filter paper.…”

Biosynthesis and function of polyacetylenes and allied natural products

“…Labeling studies with [1,2-13 C 2 ]acetate showed a contiguous series of nine intact acetate units terminated by a methyl-derived acetate carbon at C-1 of 9D. A Hock rearrangement similar to that involved in divinyl ether synthesis [168], has been proposed that is initiated from a 6-hydroperoxide species and followed by an allene-acetylene isomerization cumulatively attaching the oxygen atom to the acetylenic ether and fracturing the unsaturated chain.…”

The lipoxygenase pathway in garlic (Allium sativum L.) bulbs: detection of the novel divinyl ether oxylipins

“…1) is one of the non-common routes of the plant lipoxygenase pathway. This route was discovered by Galliard and his colleagues in potato tubers [3][4][5][6]. Divinyl ether synthase from potato utilises specifically 9-HPOD and 9-HPOT.…”