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Trabajo presentado en el ISSFAL 14th International Congress, celebrado en modalidad virtual del 10 al 14 de mayo de 2021., Isolation and functional characterisation of methyl-end (ωx) desaturases from the common ragworm Hediste diversicolor

Table 1 (primer sequences and PCR conditions); Table 2 (desaturase conversions in yeast)

Amino acid alignment of methyl desaturases.

Trabajo presentado en el 18th International Symposium on Fish Nutrition and Feeding (ISFNF), celebrado en Las Palmas de Gran Canaria (España), del 3 al 07 de junio de 2018

Trabajo presentado en Aquaculture Europe 2016: Food for Thought, celebrado en Edimburgo (Escocia) del 21 al 23 de septiembre de 2016, Elongation of very-long chain fatty acid (Elovl) proteins are enzymes that catalyse the condensation reaction, the first and rate-limiting step out of four sequential reactions required for the elongation of fatty acids (FAs) (Jakobsson et al., 2006). Seven members (Elovl1-7) make up the elongase protein family in vertebrates, with Elovl4 having a major role in the biosynthesis of very long-chain (≥ C24) FAs of both saturated and polyunsaturated (VLC-PUFA) acyl chains (Agbaga et al., 2008). Recent studies have shown that fish possess two different forms of Elovl4, namely Elovl4a and Elovl4b, with different functions and spatial-temporal expression patterns during development (Monroig et al., 2010). We have recently initiated the investigation of Elovl and fatty acyl desaturase (Fads) genes that participate in the biosynthesis of essential FAs in Clarias gariepinus, a commercially important fish species in Africa (Oboh et al., 2016). In this study, we aimed to characterise both molecularly and functionally two elovl4 cDNAs from C. gariepinus, and investigate their tissue distribution, This work was also funded by the Spanish Government grant LONGFAQUA (AGL2013-40986-R).

Fish differ in their capacity for endogenous synthesis of long-chain (C20-24) polyunsaturated fatty acids (LC-PUFA) from dietary C18 precursors (α-linolenic and linoleic acids). Understanding this capacity is of benefit to fish feed formulation. This, together with the importance of fish as the primary source of omega-3 LC-PUFA in the human diet has necessitated the rigorous study of the biochemical and molecular mechanisms involved in the LC-PUFA biosynthesis pathway in fish species. Studies have shown the potential of a species for LC-PUFA biosynthesis is associated with the complement and function of fatty acyl desaturase (fads) and elongase of very long chain fatty acid (elovl) gene it possesses. The present study therefore aimed to investigate these genes in the African catfish (Clarias gariepinus), the most commercially important farmed fish species in Sub-Saharan Africa. A fads2 and an elovl2 cDNA were cloned containing open reading frames (ORF) of 1338 base pair (bp) and 864 bp specifying proteins of 445 and 287 amino acids, respectively. Functional characterisation by heterologous expression in yeast showed that the Fads2 was bifunctional with ∆5∆6 activities catalysing the desaturation of both 18:3n-3 and 20:4n-3 and their corresponding n-6 fatty acids, 18:2n-6 and 20:3n-6. The Elovl2 showed activity towards C18, C20 and C22 PUFA with highest activity towards C20 and C22 PUFA. Tissue expression analysis showed a typical freshwater species expression pattern; higher expression in the liver compared to brain and all other tissues with the exception of elovl5 which showed highest expression in the intestine. Consistent with feeding studies of typical freshwater fish species that show their essential fatty acid requirement can be satisfied by dietary C18 PUFA, the present study confirms that the LC-PUFA biosynthesis pathway is active in the African catfish C. gariepinus.