Barramundi (Lates calcarifer) desaturase with Δ6/Δ8 dual activities
Barramundi is a commercially farmed fish in Australia. To examine the potential for barramundi to metabolise dietary α-linolenic acid (ALA, 18:3 n-3), the existence of barramundi desaturase enzymes was examined. A putative fatty acid Δ6 desaturase was cloned from barramundi liver and expressed in yeast. Functional expression revealed Δ6 desaturase activity with both the 18 carbon (C18) and C24 n-3 fatty acids, ALA and 24:5 n-3 as well as the C18 n-6 fatty, linoleic acid (LA, 18:2 n-6). Metabolism of ALA was favoured over LA. The enzyme also had Δ8 desaturase activity which raises the potential for synthesis in barramundi of omega-3 (n-3) long chain polyunsaturated fatty acids from ALA via a pathway that bypasses the initial Δ6 desaturase step. Our findings not only provide molecular evidence for the fatty acid desaturation pathway in the barramundi but also highlight the importance of taking extracellular fatty acid levels into account when assessing enzyme activity expressed in Saccharomyces cerevisiae.
KeywordsBarramundi Δ6 desaturase Extracellular fatty acids α-Linolenic acid Lipid metabolism n-3 LCPUFA
- Hastings N, Agaba MK, Tocher DR, Zheng X, Dickson CA, Dick JR, Teale AJ (2004) Molecular cloning and functional characterization of fatty acyl desaturase and elongase cDNAs involved in the production of eicosapentaenoic and docosahexaenoic acids from α-linolenic acid in Atlantic salmon (Salmo salar). Mar Biotechnol 6:463–474PubMedCrossRefGoogle Scholar
- Tocher DR, Carr J, Sargent JR (1989) Polyunsaturated fatty acid metabolism in fish cells: differential metabolism of (n-3) and (n-6) series acids by cultured cells originating from a freshwater teleost fish and from a marine teleost fish. Comp Biochem Physiol 94:367–374Google Scholar
- Tocher D, Zheng X, Schlechtriem C, Hastings N, Dick J, Teale A (2006) Highly unsaturated fatty acid synthesis in marine fish: Cloning, functional characterization, and nutritional regulation of fatty acyl delta 6 desaturase of Atlantic cod (Gadus morhua L.). Lipids 41:1003–1016PubMedCrossRefGoogle Scholar