Formation of conjugated Delta11Delta13-double bonds by Delta12-linoleic acid (1,4)-acyl-lipid-desaturase in pomegranate seeds.
For the biosynthesis of punicic acid (18:3Delta9Z,11E,13Z) a (11,14)-linoleoyl desaturase activity has been proposed. To isolate this acyl-lipid-desaturase, PCR-based cloning was used. This approach resulted in the isolation of two complete cDNAs. The first isolated full-length cDNA harbors a sequence of 1350 bp encoding a protein of 395 amino acids. The second cDNA was 1415 bp long encoding a protein of 387 amino acids. For functional identification proteins encoded by the cDNAs were expressed in Saccharomyces cerevisiae, and formation of newly formed fatty acids was analyzed by gas chromatography-free induction decay (GC-FID) and GC/MS. The expression of the heterologous enzymes resulted in the first case in a significant amount of linoleic acid and in the second case, after linoleic acid supplementation, in formation of punicic acid. The results presented here identify one cDNA coding for a classical Delta12-acyl-lipid-desaturase. The other one codes for a new type of (1,4)-acyl-lipid-desaturase that converts a cis double bond located in the Delta12-position of linoleic acid or gamma-linolenic acid, but not in alpha-linolenic acid, into a conjugated cis-trans double bond system.
D000595:Amino Acid Sequence; D001483:Base Sequence; D002849:Chromatography, Gas; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism*; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D019787:Linoleic Acid / Q000737:chemistry / Q000378:metabolism; D029561:Lythraceae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D012639:Seeds / Q000201:enzymology; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D018076:DNA, Complementary; D018744:DNA, Plant; D005227:Fatty Acids; D011994:Recombinant Proteins; D019787:Linoleic Acid; D044943:Fatty Acid Desaturases; C040448:delta-12 fatty acid desaturase