Phosphopantetheinyl transferase (PPTase) can change the acyl-carrier protein (ACP) from an inactive apo-ACP to an active holo-ACP that plays a key role in fatty acids biosynthesis. Currently, the PPTase has been proved to be involved in the biosynthesis of polyunsaturated fatty acids (PUFAs) via a polyketide synthase (PKS) pathway in Thraustochytrids, while its characteristics are not clarified. Here, the heterologous PPTase gene (pfaE) from bacteria was first co-expressed with the PKS system (orfA–orfC) from Thraustochytrid Aurantiochytrium. Then, a new endogenous PPTase (ppt_a) in Aurantiochytrium was identified by homologous alignment and its function was verified in E. coli. Moreover, the endogenous ppt_a was then overexpressed in Aurantiochytrium, and results showed that the production and proportion of PUFAs, especially docosahexaenoic acid (DHA), in the transformant SD116::PPT_A were increased by 35.5% and 17.6%, respectively. Finally, higher DHA and PUFA proportion (53.9% and 64.5% of TFA, respectively) were obtained in SD116::PPT_A using a cerulenin feeding strategy. This study has illustrated a PUFAs-synthase-specific PPTase in PKS system and provided a new strategy to improve the PUFA production in Thraustochytrids.

中文翻译：

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PUFA 合酶特异性 PPTase 通过 Aurantiochytrium 中的聚酮化合物合酶途径增强多不饱和脂肪酸的生物合成。

磷酸泛酰巯基乙炔基转移酶 (PPTase) 可以将酰基载体蛋白 (ACP) 从无活性的 apo-ACP 转变为在脂肪酸生物合成中起关键作用的活性全 ACP。目前，已证实PPTase在破囊壶菌中通过聚酮化合物合酶(PKS)途径参与多不饱和脂肪酸(PUFAs)的生物合成，但其特征尚不明确。在这里，来自细菌的异源 PPTase 基因 (pfaE) 首先与来自 Thraustochytrid Aurantiochytrium 的 PKS 系统 (orfA-orfC) 共表达。然后，通过同源比对鉴定了Aurantiochytrium中的一种新的内源性PPTase（ppt_a），并在大肠杆菌中验证了其功能。此外, 内源性 ppt_a 然后在 Aurantiochytrium 中过表达, 结果表明 PUFAs 的产生和比例, 特别是二十二碳六烯酸（DHA），在转化体 SD116::PPT_A 中分别增加了 35.5% 和 17.6%。最后，使用 cerulenin 喂养策略在 SD116::PPT_A 中获得了更高的 DHA 和 PUFA 比例（分别为 TFA 的 53.9% 和 64.5%）。本研究阐明了 PKS 系统中的一种 PUFAs 合酶特异性 PPTase，并为提高 Thraustochytrids 中 PUFA 的产量提供了新的策略。