Investigation of highly unsaturated fatty acid metabolism in the Asian sea bass, Lates calcarifer

• Published in: Fish physiology and biochemistry Vol. 36; no. 4; pp. 827 - 843
• Main Authors: Mohd-Yusof, N. Y, Monroig, O, Mohd-Adnan, A, Wan, K.-L, Tocher, D. R
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01-12-2010; Springer Netherlands; Springer Nature B.V
• Subjects: Acetyltransferases - genetics; Acetyltransferases - metabolism; Animal Anatomy; Animal Biochemistry; Animal Physiology; Animals; Aquaculture; Aquaculture - methods; Bass - metabolism; Biomedical and Life Sciences; Biosynthesis; Brain - metabolism; cDNA; Cloning; Cloning, Molecular; Computational Biology; Desaturase; Dicentrarchus labrax; DNA Primers - genetics; Docosahexaenoic Acids - metabolism; Elongase; Enterocytes - metabolism; Enzymes; Fatty acid; Fatty Acid Desaturases - genetics; Fatty Acid Desaturases - metabolism; Fatty acids; Fatty Acids, Unsaturated - biosynthesis; Fatty Acids, Unsaturated - metabolism; Freshwater & Marine Ecology; Functional characterization; Gene Expression Profiling; Hepatocytes - metabolism; Histology; Lates calcarifer; Life Sciences; Marine; Marine fish; Metabolism; Morphology; Nutrition; Reverse Transcriptase Polymerase Chain Reaction; Saccharomyces cerevisiae; Trout; Vegetable oils; Zoology; Selangor Malaysia; Malaysia; INW, Asia; ISEW, Malaysia; Australia; Elongase; cDNA; Metabolism; Desaturase; Functional characterization; Fatty acid
• ISSN: 0920-1742; 1573-5168
• DOI: 10.1007/s10695-010-9409-4

Lates calcarifer, commonly known as the Asian sea bass or barramundi, is an interesting species that has great aquaculture potential in Asia including Malaysia and also Australia. We have investigated essential fatty acid metabolism in this species, focusing on the endogenous highly unsaturated fatty acid (HUFA) synthesis pathway using both biochemical and molecular biological approaches. Fatty acyl desaturase (Fad) and elongase (Elovl) cDNAs were cloned and functional characterization identified them as ∆6 Fad and Elovl5 elongase enzymes, respectively. The ∆6 Fad was equally active toward 18:3n-3 and 18:2n-6, and Elovl5 exhibited elongation activity for C₁₈₋₂₀ and C₂₀₋₂₂ elongation and a trace of C₂₂₋₂₄ activity. The tissue profile of gene expression for ∆6 fad and elovl5 genes, showed brain to have the highest expression of both genes compared to all other tissues. The results of tissue fatty acid analysis showed that the brain contained more docosahexaenoic acid (DHA, 22:6n-3) than flesh, liver and intestine. The HUFA synthesis activity in isolated hepatocytes and enterocytes using [1-¹⁴C]18:3n-3 as substrate was very low with the only desaturated product detected being 18:4n-3. These findings indicate that L. calcarifer display an essential fatty acid pattern similar to other marine fish in that they appear unable to synthesize HUFA from C₁₈ substrates. High expression of ∆6 fad and elovl5 genes in brain may indicate a role for these enzymes in maintaining high DHA levels in neural tissues through conversion of 20:5n-3.