Cloning, tissue distribution and nutritional regulation of a Δ6-desaturase-like enzyme in rainbow trout

Characterization and comparison of fatty acyl Δ6 desaturase cDNAs from freshwater and marine teleost fish species

“…However, the cloning of the carp and turbot desaturases has given additional sequence information that has indicated that there are differences in fish desaturase sequences that may be considered as general trends. For instance, the data support the previously reported observation that salmonid desaturase genes appear to be different to the desaturases of other fish and mammalian desaturase genes in that they contain additional amino acids, having chain lengths of 454 aa (or 452 as in cherry salmon desaturase 2) compared to 444 for the cyprinid (carp and zebrafish) and human desaturases (Seiliez et al, 2001;Hastings et al, 2004). Furthermore, it was previously reported that the seabream desaturase clone encoded a protein of 445 amino acids which was one more residue than observed with the cyprinids and human desaturases (Seiliez et al, 2003).…”

“…that they included open reading frames (ORFs) of 1365 and 1338 bps (including stop codons) encoding peptides of 454 and 445 amino acids, respectively (Seiliez et al, 2001(Seiliez et al, ,2003. Sequencing of the carp and turbot desaturase cDNAs showed that they included ORFs of 1335 and 1338 bps (including stop codons), respectively, specifying proteins of 444 and 445 amino acids ( Phylogenetic analysis comparing all the putative desaturase sequences cloned from fish along with a variety of Δ5 and Δ6 desaturases from human, mouse, fungus and nematode, clustered all the 8 fish sequences together and showed they were more similar to the mammalian desaturase sequences than those of yeast and the nematode (Fig.3).…”

“…To this end, putative fatty acid cDNAs were isolated and cloned from common carp (Cyprinus carpio) and turbot (Psetta maximus). Along with cDNAs previously cloned from rainbow trout (Oncorhynchus mykiss) (Seiliez et al, 2001) and gilthead seabream (Sparus aurata) (Seiliez et al, 2003), the enzymic activities of all four clones were determined by heterologous expression in the yeast, Saccharomyces cerevisiae. The results showed that all the cDNAs encoded basically unifunctional Δ6 fatty acid desaturase enzymes responsible for the first and, reportedly, rate-limiting, step in the biosynthesis of HUFA from C 18 PUFA.…”

“…AF301910) and gilthead sea bream (Sparus aurata, GenBank, accession no. AY055749) based on sequence similarity to mammalian Δ6 fatty acid desaturases as described in detail previously (Seiliez et al, 2001(Seiliez et al, ,2003.…”

“…However, although further fatty acid desaturase genes are likely to be identified in these species, the desaturases already cloned from fish species including carp, trout, turbot, sea bream and salmon is important as these are species in which there is a relative wealth of data on the nutritional regulation of fatty acid desaturation and HUFA synthesis, and in which substantive differences occur between species Tocher, 2003). Gene expression studies have shown that transcriptional regulation of desaturase occurs in fish (Seiliez et al, 2001(Seiliez et al, ,2003Zheng et al, 2004), but further studies are in progress to characterise the factors such as SREBP-1c and PPARs that are likely to be important in controlling the regulation of these enzyme activities in fish Nara, 2002,2003).…”