Analysis of Δ12-fatty acid desaturase function revealed that two distinct pathways are active for the synthesis of PUFAs in T. aureum ATCC 34304

Thraustochytrids are known to synthesize PUFAs such as docosahexaenoic acid (DHA). Accumulating evidence suggests the presence of two synthetic pathways of PUFAs in thraustochytrids: the polyketide synthase-like (PUFA synthase) and desaturase/elongase (standard) pathways. It remains unclear whether the latter pathway functions in thraustochytrids. In this study, we report that the standard pathway produces PUFA in Thraustochytrium aureum ATCC 34304. We isolated a gene encoding a putative Delta 12-fatty acid desaturase (Tau Delta 12des) from T. aureum. Yeasts transformed with the tau Delta 12des converted endogenous oleic acid (OA) into linoleic acid (LA). The disruption of the tau Delta 12des in T. aureum by homologous recombination resulted in the accumulation of OA and a decrease in the levels of LA and its downstream PUFAs. However, the DHA content was increased slightly in tau Delta 12des-disruption mutants, suggesting that DHA is primarily produced in T. aureum via the PUFA synthase pathway. The transformation of the tau Delta 12des-disruption mutants with a tau Delta 12des expression cassette restored the wild-type fatty acid profiles. These data clearly indicate that Tau Delta 12des functions as Delta 12-fatty acid desaturase in the standard pathway of T. aureum and demonstrate that this thraustochytrid produces PUFAs via both the PUFA synthase and the standard pathways.-Matsuda, T., K. Sakaguchi, R. Hamaguchi, T. Kobayashi, E. Abe, Y. Hama, M. Hayashi, D. Honda, Y. Okita, S. Sugimoto, N. Okino, and M. Ito. Analysis of Delta 12-fatty acid desaturase function revealed that two distinct pathways are active for the synthesis of PUFAs in T. aureum ATCC 34304. J. Lipid Res. 2012. 53: 1210-1222.