Teleost fatty acyl desaturase genes : a comparative study.

• Main Author: Hastings, Nicola
• Other Authors: Aquaculture
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stirling 2003
• Subjects: Osteichthyes; Fatty acids Metabolism Regulatio; Fishes Genetics; Atlantic salmon; Turbot
• Online Access: http://hdl.handle.net/1893/30778; http://dspace.stir.ac.uk/bitstream/1893/30778/1/13916327.pdf

Marine teleosts, unlike their freshwater counterparts, have a repressed ability to synthesise long chain highly unsaturated fatty acids (HUPA). In competent species, the A6 and A5 fatty acid desaturases are critical in the biosynthetic pathway that produces the HUFA’s arachidonic acid (20:4/z-6; AA), eicosapentaenoic acid (20:5n3; EPA) and docosahexaenoic acid (22:6/z-3; DHA) from the Ci8 polyunsaturated fatty acids (PUFA), linoleic acid (18:2/2-6) and a-linolenic acid (18:3/2-3). The deficiency in HUFA biosynthesis in marine fish is of considerable practical significance because, in consequence, farmed marine species require a dietary source of presynthesised HUFA. This is provided by processed products from “industrial” species of marine fish such as sand eel, sardine, capelin and anchovies which themselves obtain HUFA through the food chain. Indicators suggest that the wild fishery supporting the aquaculture feed industry is unsustainable at current levels of exploitation. This has consequential effects on human health as fish, especially marine fish, are the predominant dietary source of HUFA that are crucial for maintaining cell membrane integrity as well as being central to eicosanoid metabolism. Therefore, the primary aims of this project were to further our understanding of the molecular differences in HUFA biosynthesis between marine and freshwater teleosts. This was achieved by comparing the fatty acid desaturase genes of representative marine and freshwater fish. The desaturases are enzymes involved in the biosynthesis of HUFA from PUFA and have been considered as one of the steps that may be compromised in marine fish. The desaturase genes were studied with a view to relating structural, and potential functional differences with different HUFA synthesis phenotypes. During the course of this project sequences of putative desaturase genes were cloned from two freshwater (zebrafish and carp), two marine (turbot and cod) and one anadromous fish species (Atlantic salmon). Once translated, the protein ...