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Polyunsaturated aldehydes (PUAs) are a group of allelopathic chemicals typically associated with diatom-copepod predator-prey interactions.〔Miller, Charles B. Biological Oceanography. Malden, MA: Blackwell Pub., 2004. Print.〕 These compounds are classified by an aldehyde group covalently bound to long carbon chains containing two or more carbon-carbon double bonds. Examples include isomers of heptadienal, octadienal, octatrienal, and decatrienal.〔Solomons, T. W. Graham., and Craig B. Fryhle. Organic Chemistry. Hoboken, NJ: John Wiley, 2008. Print.〕 ==Production by diatoms== Polyunsaturated aldehydes are oxylipins that are formed from lipids (specifically the fatty acid portion of lipids) when diatoms are exposed to environmental stresses. Stresses can include nutrient limitations, grazing by predators, and wounding.〔Schilmiller, Anthony L., and Gregg A. Howe. "Systemic Signaling in the Wound Response." Current Opinion in Plant Biology 8.4 (2005): 369-77. Web.〕 In particular, damage to diatom cells as a result of grazing by zooplankton invokes a chemical defense mechanism that produces PUA’s as secondary metabolites from fatty acids.〔Fontana, Angelo, Giuliana D'ippolito, Adele Cutignano, Antonio Miralto, Adrianna Ianora, Giovanna Romano, and Guido Cimino. "Chemistry of Oxylipin Pathways in Marine Diatoms." Pure and Applied Chemistry 79.4 (2007): n. pag. Web.〕 The production mechanism is as follows: # Grazing by predators results in diatom cell membrane disruption. # Enzymes (lipases) are produced in response to the damaged membranes. These enzymes make contact with newly freed phospholipids (from cell membranes) and catalyze the formation of polyunsaturated fatty acids.〔Ribalet, François, Mauro Bastianini, Charles Vidoudez, Francesco Acri, John Berges, Adrianna Ianora, Antonio Miralto, Georg Pohnert, Giovanna Romano, Thomas Wichard, and Raffaella Casotti. "Phytoplankton Cell Lysis Associated with Polyunsaturated Aldehyde Release in the Northern Adriatic Sea." PLoS ONE 9.1 (2014): n. pag. Web.〕 # The enzyme lipoxygenase then catalyzes the reaction of fatty acids to polyunsaturated aldehydes, which are then directly exposed to the grazing zooplankton.〔Barofsky, Alexandra, and Georg Pohnert. "Biosynthesis of Polyunsaturated Short Chain Aldehydes in the Diatom Thalassiosira Rotula." Org. Lett. Organic Letters 9.6 (2007): 1017-020. Web.〕 ''Thalassiosira rotula'' represents the most well-studied diatom species in terms of polyunsaturated aldehyde production. Wichard et al. determined that only 30% of PUA precursor molecules remain in ''T. rotula'' within minutes of cell membrane wounding, indicating a fast rate of response by diatoms to zooplankton grazing.〔Wichard, Thomas, Andrea Gerecht, Maarten Boersma, Serge A. Poulet, Karen Wiltshire, and Georg Pohnert. "Lipid and Fatty Acid Composition of Diatoms Revisited: Rapid Wound-Activated Change of Food Quality Parameters Influences Herbivorous Copepod Reproductive Success." ChemBioChem 8.10 (2007): 1146-153. Web.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Polyunsaturated aldehyde」の詳細全文を読む スポンサード リンク
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