title: Identification and functional characterisation of genes encoding the omega-3 polyunsaturated fatty acid biosynthetic pathway from the coccolithophore Emiliania huxleyi.
abstract: 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.
authors.affiliation: Department of Biological Chemistry, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK.
authors.forename: Olga
authors.initials: O
authors.lastname: Sayanova
authors.forename: Richard P
authors.initials: RP
authors.lastname: Haslam
authors.forename: Monica Venegas
authors.initials: MV
authors.lastname: Calerón
authors.forename: Noemi Ruiz
authors.initials: NR
authors.lastname: López
authors.forename: Charlotte
authors.initials: C
authors.lastname: Worthy
authors.forename: Paul
authors.initials: P
authors.lastname: Rooks
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Allen
authors.forename: Johnathan A
authors.initials: JA
authors.lastname: Napier
mesh_terms: D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism; D000214:Acyl Coenzyme A / Q000378:metabolism; D053898:Biosynthetic Pathways / Q000235:genetics*; D019295:Computational Biology / Q000379:methods*; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism; D000081031:Fatty Acid Elongases; D015525:Fatty Acids, Omega-3 / Q000096:biosynthesis*; D058087:Haptophyta / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics
chemical_list: D000214:Acyl Coenzyme A; D015525:Fatty Acids, Omega-3; D044943:Fatty Acid Desaturases; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases