Novel fatty acid elongases and their use for the reconstitution of docosahexaenoic acid biosynthesis.
In algae, the biosynthesis of docosahexaenoic acid (22:6omega3; DHA) proceeds via the elongation of eicosapentaenoic acid (20:5omega3; EPA) to 22:5omega3, which is required as a substrate for the final Delta4 desaturation. To isolate the elongase specific for this step, we searched expressed sequence tag and genomic databases from the algae Ostreococcus tauri and Thalassiosira pseudonana, from the fish Oncorhynchus mykiss, from the frog Xenopus laevis, and from the sea squirt Ciona intestinalis using as a query the elongase sequence PpPSE1 from the moss Physcomitrella patens. The open reading frames of the identified elongase candidates were expressed in yeast for functional characterization. By this, we identified two types of elongases from O. tauri and T. pseudonana: one specific for the elongation of (Delta6-)C18-PUFAs and one specific for (Delta5-)C20-PUFAs, showing highest activity with EPA. The clones isolated from O. mykiss, X. laevis, and C. intestinalis accepted both C18- and C20-PUFAs. By coexpression of the Delta6- and Delta5-elongases from T. pseudonana and O. tauri, respectively, with the Delta5- and Delta4-desaturases from two other algae we successfully implemented DHA synthesis in stearidonic acid-fed yeast. This may be considered an encouraging first step in future efforts to implement this biosynthetic sequence into transgenic oilseed crops.
Meyer
Astrid
A
Biozentrum Klein Flottbek, Universität Hamburg, D-22609 Hamburg, Germany.
Kirsch
Helene
H
Domergue
Frédéric
F
Abbadi
Amine
A
Sperling
Petra
P
Bauer
Jörg
J
Cirpus
Petra
P
Zank
Thorsten K
TK
Moreau
Hervé
H
Roscoe
Thomas J
TJ
Zähringer
Ulrich
U
Heinz
Ernst
E
D000123:Acetyltransferases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D019068:Bryopsida / Q000201:enzymology; D002938:Ciona intestinalis / Q000201:enzymology; D003001:Cloning, Molecular; D004281:Docosahexaenoic Acids / Q000737:chemistry / Q000378:metabolism*; D056890:Eukaryota / Q000201:enzymology; D019143:Evolution, Molecular; D000081031:Fatty Acid Elongases; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D008722:Methods; D017686:Oncorhynchus mykiss / Q000378:metabolism; D010802:Phylogeny; D016415:Sequence Alignment; D013379:Substrate Specificity; D014982:Xenopus laevis / Q000378:metabolism; D015003:Yeasts / Q000235:genetics
D005231:Fatty Acids, Unsaturated; D004281:Docosahexaenoic Acids; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases