title: Characterization of both polyunsaturated fatty acid biosynthetic pathways in Schizochytrium sp.
abstract: Schizochytrium produces long chain polyunsaturated fatty acids (PUFAs) via a PUFA synthase. Targeted mutagenesis of one gene of this synthase was conducted to confirm PUFA synthase function and determine its metabolic necessity. The resulting mutants were auxotrophic and required supplementation with PUFAs. In vivo labeling experiments with radioactive fatty acids demonstrated the presence of several elongase and desaturase activities associated with the standard pathway of PUFA synthesis. However, this system was missing a critical Delta12 desaturase activity and was therefore not capable of synthesizing PUFAs from the 16- or 18-carbon saturated fatty acid products of the fatty acid synthase. Because Schizochytrium uses a PUFA synthase system for the production of PUFAs, the existence of a partial desaturase-elongase system (if not a simple vestige) is suggested to be either a scavenging mechanism for intermediate fatty acids prematurely released by the PUFA synthase or for PUFAs found in the organism's native environment.
authors.affiliation: Martek Biosciences Corporation, 6480 Dobbin Rd, Columbia, MD 21045-5825, USA. clippmeier@martek.com
authors.forename: J Casey
authors.initials: JC
authors.lastname: Lippmeier
authors.forename: Kristine S
authors.initials: KS
authors.lastname: Crawford
authors.forename: Carole B
authors.initials: CB
authors.lastname: Owen
authors.forename: Angie A
authors.initials: AA
authors.lastname: Rivas
authors.forename: James G
authors.initials: JG
authors.lastname: Metz
authors.forename: Kirk E
authors.initials: KE
authors.lastname: Apt
mesh_terms: D002478:Cells, Cultured; D003001:Cloning, Molecular; D017377:Diatoms / Q000235:genetics / Q000378:metabolism*; D054889:Fatty Acid Synthase, Type II / Q000235:genetics; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis*; D050356:Lipid Metabolism / Q000235:genetics*; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D030781:Organisms, Genetically Modified; D010084:Oxidation-Reduction
chemical_list: D005231:Fatty Acids, Unsaturated; D054889:Fatty Acid Synthase, Type II