Journal
MARINE DRUGS
Volume 12, Issue 3, Pages 1317-1334Publisher
MDPI AG
DOI: 10.3390/md12031317
Keywords
Phaeodactylum Delta 5-elongase; diatom fatty acids metabolites; functional stacking of ELO5 and FAD4
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Funding
- National 863 High Tech Project of China [2011AA100904]
- National Natural Science Foundation of China [31270346]
- Oil Crops Research Institute [2013HT005]
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The diatom Phaeodactylum tricornutum can accumulate eicosapentaenoic acid (EPA) up to 30% of the total fatty acids. This species has been targeted for isolating gene encoding desaturases and elongases for long-chain polyunsaturated fatty acid (LC-PUFA) metabolic engineering. Here we first report the cloning and characterization of Delta 5-elongase gene in P. tricornutum. A full-length cDNA sequence, designated PhtELO5, was shown to contain a 1110 bp open reading frame encoding a 369 amino acid polypeptide. The putative protein contains seven transmembrane regions and two elongase characteristic motifs of FLHXYHH and MYSYY, the latter being typical for microalgal Delta 5-elongases. Phylogenetic analysis indicated that PhtELO5 belongs to the ELO5 group, tightly clustered with the counterpart of Thalassiosira pseudonana. Heterologous expression of PhtELO5 in Pichia pastoris confirmed that it encodes a specific Delta 5-elongase capable of elongating arachidonic acid and eicosapentaenoic acid. Co-expression of PhtELO5 and IsFAD4 (a increment 4-desaturase from Isochrysis sphaerica) demonstrated that the high-efficiency biosynthetic pathway of docosahexaenoic acid was assembled in the transgenic yeast. Substrate competition revealed that PhtELO5 exhibited higher activity towards n-3 PUFA than n-6 PUFA. It is hypothesized that Phaeodactylum ELO5 may preferentially participate in biosynthesis of transgenic LC-PUFA via a n-3 pathway in the yeast host.
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