Δ12-Oleate Desaturase-related Enzymes Associated with Formation of Conjugated trans-Δ11, cis-Δ13 Double Bonds

Abstract

Conjugated linolenic acids are present as major seed oils in several plant species. Punicic acid (or trichosanic acid) is a conjugated linolenic acid isomer containing cis-⌬9, trans-⌬11, cis-⌬13 double bonds in the C 18 carbon chain. Here we report cDNAs, TkFac and PgFac, isolated from Trichosanthes kirilowii and Punica granatum, that encode a class of conjugases associated with the formation of trans-⌬11, cis-⌬13 double bonds. Expression of TkFac and PgFac in Arabidopsis seeds under transcriptional control of the seed-specific napin promoter resulted in accumulation of punicic acid up to ϳ10% (w/w) of the total seed oils. In contrast, no punicic acid was found in lipids from leaves even when the conjugases were driven under control of the cauliflower mosaic virus 35S promoter. :3⌬ 9cis, 12cis, 15cis ) acids. These are typical fatty acids with all other fatty acids regarded as unusual. Typically, polyunsaturation of fatty acids is methylene (-CH 2 -)-interrupted and occurs in cis-configuration as found in linoleic and linolenic acids. In contrast, conjugated (non-methylene-interrupted) fatty acids contain double bonds in cis-or trans-configuration. The conjugated fatty acids occur as diene, triene, and tetraene in which the most common conjugated polyenoic acids are octadecatrienoic acids, termed CLNAs.

Involvement of a bifunctional fatty-acyl desaturase in the biosynthesis of the silkmoth, Bombyx mori , sex pheromone

“…It is known that some higher plants accumulate conjugated linolenic acids as major components of seed oils (22). In the biosynthesis of conjugated linolenic acids, enzymes termed conjugases catalyze the formation of conjugated double bonds; the Z12 double bond of linoleic acid, for instance, is converted into the two E11 and E13 double bonds found in ␣-eleostearic acid (23).…”

“…In the biosynthesis of conjugated linolenic acids, enzymes termed conjugases catalyze the formation of conjugated double bonds; the Z12 double bond of linoleic acid, for instance, is converted into the two E11 and E13 double bonds found in ␣-eleostearic acid (23). Recently, several plant seed cDNAs encoding conjugases have been characterized (22)(23)(24)(25). Interestingly, one such conjugase associated with the formation of the E11,Z13-diene in punicic acid (22) has been reported to exhibit both Z12 desaturation and E11,Z13-conjugation activities.…”

“…Recently, several plant seed cDNAs encoding conjugases have been characterized (22)(23)(24)(25). Interestingly, one such conjugase associated with the formation of the E11,Z13-diene in punicic acid (22) has been reported to exhibit both Z12 desaturation and E11,Z13-conjugation activities. This enzyme, however, shares only 28% amino acid identity with B. mori Desat1.…”

Isoetin 5'-Methyl Ether, A Cytotoxic Flavone from Trichosanthes kirilowii

“…Aqueous methanolic layer was concentrated to give brownish residue (98 g) that was partitioned between H 2 O (1.2 L) and CH 2 Cl 2 (1.2 L × 5). The CH 2 Cl 2 layer (30 g, IC 50 ~100 μg/mL against A549) was chromatographed on a flash column with elution of a mixture of CH 2 Cl 2 , MeOH, and H 2 O of increasing polarity to yield fourteen fractions (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Among these, fraction 4 (6.9 g) showed cytotoxicity with an IC 50 range of 20-40 μg/mL, was further subjected to silica column chromatography with gradient elution of a mixture of hexane, EtOAc, and MeOH to give ten subfractions.…”

“…Trichosanic acid (punicic acid) has been long known from this plant as conjugated linolenic acid with recent evidence showing cytotoxic effect on tumor cells and beneficial effect on lipid metabolism. [3][4][5][6] A ribosome-inactivating protein trichosanthin with 27 kDa consisting of 289 amino acids has been found to have abortifacient, antitumor, immunosuppressive, and anti-HIV activities. [7][8][9][10][11][12] Glycan trichosans isolated from the aqueous extract of this plant have been shown to reduce the plasma glucose level in mice.…”