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Highly unsaturated fatty acid synthesis in vertebrates: New insights with the cloning and characterization of a Δ6 desaturase of Atlantic salmon

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Lipids

Abstract

Fish are an important source of the n−3 highly unsaturated fatty acids (HUFA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids that are crucial to the health of higher vertebrates. The synthesis of HUFA involves enzyme-mediated desaturation, and a Δ5 fatty acyl desaturase cDNA has been cloned from Atlantic salmon (Salmo salar) and functionally characterization of a Δ6 fatty acyl desaturase of Atlantic salmon and describe its genomic structure, tissue expression, and nutritional regulation. A salmon genomic library was screened with a salmon Δ5 desaturase cDNA and positive recombinant phage isolated and subcloned. The full-length cDNA for the putative fatty acyl desaturase was shown to comprise 2106 bp containing an open reading frame of 1365 bp specifying a protein of 454 amino acids (GenBank accession no. AY458652). The protein sequence included three histidine boxes, two transmembrane regions, and an N-terminal cytochrome b5 domain containing the heme-binding motif HPGG, all of which are characteristic of microsomal fatty acid desaturases. Functional expression showed that this gene possessed predominantly Δ6 desaturase activity. Screening and sequence analysis of the genomic DNA of a single fish revealed that the Δ6 desaturase gene constituted 13 exons in 7965 bp of genomic DNA. Quantitative real-time PCR assay of gene expression in Atlantic salmon showed that both Δ6 and Δ5 fatty acyl desaturase genes, and a fatty acyl elongase gene, were highly expressed in intestine, liver, and brain, and less so in kidney, heart, gill, adipose tissue, muscle, and spleen. Furthermore, expression of both Δ6 and Δ5 fatty acyl desaturase genes in intestine, liver, red muscle, and adipose tissue was higher in salmon fed a diet containing vegetable oil than in fish fed a diet containing fish oil.

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Abbreviations

FO:

fish oil

HUFA:

highly unsaturated fatty acids (carbon chain length ≥20 with ≥3 double bonds)

MMLV:

Moloney murine leukemia virus

ORF:

open reading frame

qrtPCR:

quantitative (real-time) polymerase chain reaction

RACE:

rapid amplification of cDNA ends

SCMM:

Saccharomyces cerevisiae minimal medium

UTR:

untranslated region

VO:

vegetable oil

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Authors and Affiliations

  1. Institute of Aquaculture, University of Stirling, FK9 4LA, Stirling, Scotland, UK

    Xiaozhong Zheng, Douglas R. Tocher, Cathryn A. Dickson, J. Gordon Bell & Alan J. Teale

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  1. Xiaozhong Zheng
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  2. Douglas R. Tocher
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  3. Cathryn A. Dickson
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  4. J. Gordon Bell
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  5. Alan J. Teale
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Correspondence to Douglas R. Tocher.

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Zheng, X., Tocher, D.R., Dickson, C.A. et al. Highly unsaturated fatty acid synthesis in vertebrates: New insights with the cloning and characterization of a Δ6 desaturase of Atlantic salmon. Lipids 40, 13–24 (2005). https://doi.org/10.1007/s11745-005-1355-7

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  • DOI: https://doi.org/10.1007/s11745-005-1355-7

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