title: Isolation and Functional Characterisation of a fads2 in Rainbow Trout (Oncorhynchus mykiss) with Δ5 Desaturase Activity.
abstract: Rainbow trout, Oncorhynchus mykiss, are intensively cultured globally. Understanding their requirement for long-chain polyunsaturated fatty acids (LC-PUFA) and the biochemistry of the enzymes and biosynthetic pathways required for fatty acid synthesis is important and highly relevant in current aquaculture. Most gnathostome vertebrates have two fatty acid desaturase (fads) genes with known functions in LC-PUFA biosynthesis and termed fads1 and fads2. However, teleost fish have exclusively fads2 genes. In rainbow trout, a fads2 cDNA had been previously cloned and found to encode an enzyme with Δ6 desaturase activity. In the present study, a second fads2 cDNA was cloned from the liver of rainbow trout and termed fads2b. The full-length mRNA contained 1578 nucleotides with an open reading frame of 1365 nucleotides that encoded a 454 amino acid protein with a predicted molecular weight of 52.48 kDa. The predicted Fads2b protein had the characteristic traits of the microsomal Fads family, including an N-terminal cytochrome b5 domain containing the heme-binding motif (HPPG), histidine boxes (HDXGH, HFQHH and QIEHH) and three transmembrane regions. The fads2b was expressed predominantly in the brain, liver, intestine and pyloric caeca. Expression of the fasd2b in yeast generated a protein that was found to specifically convert eicosatetraenoic acid (20:4n-3) to eicosapentaenoic acid (20:5n-3), and therefore functioned as a Δ5 desaturase. Therefore, rainbow trout have two fads2 genes that encode proteins with Δ5 and Δ6 desaturase activities, respectively, which enable this species to perform all the desaturation steps required for the biosynthesis of LC-PUFA from C18 precursors.
authors.affiliation: Deakin University, School of Life and Environmental Sciences, Waurn Ponds, Geelong, Victoria, Australia.|Universiti Sains Malaysia, School of Biological Sciences, Penang, Malaysia.
authors.forename: Noor Khalidah
authors.initials: NK
authors.lastname: Abdul Hamid
authors.affiliation: University of Stirling, Institute of Aquaculture, School of Natural Sciences, Stirling, Scotland, United Kingdom.
authors.forename: Greta
authors.initials: G
authors.lastname: Carmona-Antoñanzas
authors.affiliation: University of Stirling, Institute of Aquaculture, School of Natural Sciences, Stirling, Scotland, United Kingdom.
authors.forename: Óscar
authors.initials: Ó
authors.lastname: Monroig
authors.affiliation: University of Stirling, Institute of Aquaculture, School of Natural Sciences, Stirling, Scotland, United Kingdom.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Tocher
authors.affiliation: Deakin University, School of Life and Environmental Sciences, Waurn Ponds, Geelong, Victoria, Australia.
authors.forename: Giovanni M
authors.initials: GM
authors.lastname: Turchini
authors.affiliation: Deakin University, School of Life and Environmental Sciences, Waurn Ponds, Geelong, Victoria, Australia.
authors.forename: John A
authors.initials: JA
authors.lastname: Donald
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D044943:Fatty Acid Desaturases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D020869:Gene Expression Profiling; D008969:Molecular Sequence Data; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D010802:Phylogeny; D060888:Real-Time Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D016415:Sequence Alignment; D017423:Sequence Analysis, RNA
chemical_list: D018076:DNA, Complementary; D044943:Fatty Acid Desaturases