| Summary: | fish oil; HUFA, highly unsaturated fatty acids (carbon chain length ≥ C20 with ≥ 3 double bonds); LO, linseed oil; ORF, open reading frame; PUFA, polyunsaturated fatty acids; Q-PCR, quantitative (real-time) polymerase chain reaction; RACE, rapid amplification of cDNA ends; RO, rapeseed oil; SO, soybean oil; UTR, untranslated region; VO, vegetable oil. 2 Abstract Fish species vary in their capacity to biosynthesize the n-3 long-chain polyunsaturated fatty acids (LC-PUFA) eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids that are crucial to the health of higher vertebrates. The synthesis of LC-PUFA involves enzyme-mediated fatty acyl desaturation and elongation. Previously, a cDNA for an elongase, now termed elovl5a, had been cloned from Atlantic salmon. Here we report on the cloning of two new elongase cDNAs: a second elovl5b elongase, corresponding to a 294 aa protein, and an elovl2-like elongase, coding for a 287 aa protein, characterized for the first time in a non-mammalian vertebrate. Heterologous expression in yeast showed that the salmon Elovl5b elongated C18 and C20 PUFA, with low activity towards C22, while Elovl2 elongated C20 and C22 PUFA with lower activity towards C18 PUFA. All three transcripts showed
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