Characterization of Both Polyunsaturated Fatty Acid Biosynthetic Pathways in Schizochytrium sp.
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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 Δ12 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.
KeywordsFatty acid metabolism Metabolism Polyunsaturated fatty acids (PUFA) Specific lipids Radiotracer Analytical techniques Marine lipid biochemistry General area Molecular biology Miscellaneous
We would like to acknowledge Jerry Kuner, Brad Rosenzweig, Craig Weaver, and Dan Doherty for helpful discussions and for supplying vectors without which this work would not have been possible. We would also like to acknowledge Paul Roesseler’s development of the Schizochytrium transformation system and his observations of homologous recombination with it. Colin Ratledge is thanked for review of portions of the manuscript.
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