Identification and functional characterisation of genes encoding the omega-3 polyunsaturated fatty acid biosynthetic pathway from the coccolithophore Emiliania huxleyi

• Published in: Phytochemistry (Oxford) Vol. 72; no. 7; pp. 594 - 600
• Main Authors: Sayanova, Olga, Haslam, Richard P., Calerón, Monica Venegas, López, Noemi Ruiz, Worthy, Charlotte, Rooks, Paul, Allen, Michael J., Napier, Johnathan A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.05.2011; Elsevier
• Subjects: Acetyltransferases - genetics; Acetyltransferases - metabolism; Acyl Coenzyme A - metabolism; Biological and medical sciences; Biosynthetic Pathways - genetics; Chemical constitution; Coccolithophore; Coccolithus huxleyi; Computational Biology - methods; Desaturases; Emiliania huxleyi; Fatty Acid Desaturases - genetics; Fatty Acid Desaturases - metabolism; Fatty Acid Elongases; Fatty Acids, Omega-3 - biosynthesis; Fundamental and applied biological sciences. Psychology; Haptophyta - enzymology; Haptophyta - genetics; Haptophyta - metabolism; Omega-3 long chain polyunsaturated fatty acids; Plant physiology and development; Prymnesiophyceae; Saccharomyces cerevisiae - genetics; Emiliania huxleyi; Desaturases; Coccolithophore; Omega-3 long chain polyunsaturated fatty acids; Gene; Plant origin; Chemical structure; Polyunsaturated fatty acid; Genetics; Identification
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2011.01.022

The coccolithophore Emiliania huxleyi is an abundant marine alga and plays a key role in marine foodwebs, synthesising high levels of omega-3 long chain polyunsaturated fatty acids. Here we describe the functional characterisation of the genes for this pathway from this alga. [Display omitted] ► Emiliania huxleyi synthesises eicosapentaenoic acid via the alternative pathway. ► E. huxleyi Δ5-desaturase is an acyl-CoA-dependent enzyme. ► Although octadecapentaenoic acid is the most abundant fatty acid in E. huxleyi, it is absent from the acyl-CoA pool. The Prymnesiophyceae coccolithophore Emiliania huxleyi is one of the most abundant alga in our oceans and therefore plays a central role in marine foodwebs. E. huxleyi is notable for the synthesis and accumulation of the omega-3 long chain polyunsaturated fatty acid docosahexaenoic acid (DHA; 22:6Δ 4,7,10,13,16,19, n − 3) which is accumulated in fish oils and known to have health-beneficial properties to humans, preventing cardiovascular disease and related pathologies. Here we describe the identification and functional characterisation of the five E. huxleyi genes which direct the synthesis of docosahexaenoic acid in this alga. Surprisingly, E. huxleyi does not use the conventional Δ6-pathway, instead using the alternative Δ8-desaturation route which has previously only been observed in a few unrelated microorganisms. Given that E. huxleyi accumulates significant levels of the Δ6-desaturated fatty acid stearidonic acid (18:4Δ 6,9,12,15, n − 3), we infer that the biosynthesis of DHA is likely to be metabolically compartmentalised from the synthesis of stearidonic acid.