Microbial production of n-3 docosapentaenoic acid and development of its utilization

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n-3 Docosapentaenoic acid (DPA) exhibits suppressive effect for coronary arteriosclerosis at 10-20 times higher activity than that of eicosapentaenoic acid (EPA), a precursor of DPA.However, its physiological role has yet to be elucidated enough and market for its commercial use remains small. One of the obstacles is the lack of source to provide inexpensive and an enough amount of DPA.The aim of this study was to develop the production system of microbial DPA.First, we isolated a number of marine microbes producing polyunsaturated fatty acids and evaluated their DPA productivity. One of them, Thraustochytrium sp. strain KK17-3, contained DPA at the level of 1-3% of total intracellular fatty acids. We further improved its DPA productivity through optimization of culture condition. In order to isolate and utilize genes involving to the biosynthesis of polyunsaturated fatty acids, we tried to elucidate biosynthetic pathway of DPA in the marine microbe. As a result, a novel pathway including elongation of saturated fatty acids was found. This implied that n-6 DPA, but not n-3 DPA, was an intermediate for biosynthesis of docosahexaenoic acid (DHA), a final product of the pathway. However, we have also found that the Labyrinthula microbes contain conventional type of desaturases that are homologous to delta-12 and delta-6 desaturases from higher plants and fungi. This might indicate that n-3 DPA as well as EPA is biosynthesized along with the pathway identical to those of the most of eukaryotes. Indeed, n-3 DPA could be generated through an elongation of EPA by mammalian type of elongase.