title: Identification of a Delta 4 fatty acid desaturase from Thraustochytrium sp. involved in the biosynthesis of docosahexanoic acid by heterologous expression in Saccharomyces cerevisiae and Brassica juncea.
abstract: The existence of Delta 4 fatty acid desaturation in the biosynthesis of docosahexanoic acid (DHA) has been questioned over the years. In this report we describe the identification from Thraustochytrium sp. of two cDNAs, Fad4 and Fad5, coding for Delta 4 and Delta 5 fatty acid desaturases, respectively. The Delta 4 desaturase, when expressed in Saccharomyces cerevisiae, introduced a double bond at position 4 of 22:5(n-3) and 22:4(n-6) resulting in the production of DHA and docosapentanoic acid. The enzyme, when expressed in Brassica juncea under the control of a constitutive promoter, desaturated the exogenously supplied substrate 22:5(n-3), resulting in the production of DHA in vegetative tissues. These results support the notion that DHA can be synthesized via Delta 4 desaturation and suggest the possibility that DHA can be produced in oilseed crops on a large scale.
authors.affiliation: Department of Research and Development, Bioriginal Food and Science Corporation, Saskatoon, Saskatchewan, S7J 0R1, Canada. xqui@pbi.nrc.ca
authors.forename: X
authors.initials: X
authors.lastname: Qiu
authors.forename: H
authors.initials: H
authors.lastname: Hong
authors.forename: S L
authors.initials: SL
authors.lastname: MacKenzie
mesh_terms: D000595:Amino Acid Sequence; D001937:Brassica / Q000235:genetics*; D003001:Cloning, Molecular; D000090943:Delta-5 Fatty Acid Desaturase; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D005057:Eukaryotic Cells / Q000201:enzymology*; D044943:Fatty Acid Desaturases / Q000737:chemistry / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000235:genetics*
chemical_list: D000090943:Delta-5 Fatty Acid Desaturase; D004281:Docosahexaenoic Acids; D044943:Fatty Acid Desaturases; C434953:delta-4 fatty acid desaturase