Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
J Lipid Res. 2012 Jun;53(6):1210-22. doi: 10.1194/jlr.M024935. Epub 2012 Feb 26.
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 Δ12-fatty acid desaturase (TauΔ12des) from T. aureum. Yeasts transformed with the tauΔ12des converted endogenous oleic acid (OA) into linoleic acid (LA). The disruption of the tauΔ12des 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 tauΔ12des-disruption mutants, suggesting that DHA is primarily produced in T. aureum via the PUFA synthase pathway. The transformation of the tauΔ12des-disruption mutants with a tauΔ12des expression cassette restored the wild-type fatty acid profiles. These data clearly indicate that TauΔ12des functions as Δ12-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.
厚壳贻贝被认为可以合成多不饱和脂肪酸（PUFA），如二十二碳六烯酸（DHA）。越来越多的证据表明，厚壳贻贝中有两种多不饱和脂肪酸的合成途径：聚酮合酶样（PUFA 合酶）和去饱和酶/延长酶（标准）途径。目前尚不清楚后者途径是否在厚壳贻贝中起作用。在这项研究中，我们报告了标准途径在金黄被孢霉 ATCC 34304 中产生 PUFAs。我们从金黄被孢霉中分离出一个编码假定的 Δ12-脂肪酸去饱和酶（TauΔ12des）的基因。用 tauΔ12des 转化的酵母将内源性油酸（OA）转化为亚油酸（LA）。金黄被孢霉中 tauΔ12des 的同源重组破坏导致 OA 的积累和 LA 及其下游 PUFAs 水平的降低。然而，tauΔ12des 破坏突变体中的 DHA 含量略有增加，表明 DHA 主要通过 PUFA 合酶途径在金黄被孢霉中产生。用 tauΔ12des 表达盒转化 tauΔ12des 破坏突变体恢复了野生型脂肪酸图谱。这些数据清楚地表明，TauΔ12des 在金黄被孢霉的标准途径中作为 Δ12-脂肪酸去饱和酶发挥作用，并证明该厚壳贻贝通过 PUFA 合酶和标准途径产生 PUFAs。
