College of Marine Life Sciences, Ocean University of China, Yushan-Road, No. 5, Qingdao, China.
Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 266003 Qingdao, China.
Biochem J. 2020 Mar 13;477(5):887-903. doi: 10.1042/BCJ20190922.
So far, it has been still unknown how liamocins are biosynthesized, regulated, transported and secreted. In this study, a highly reducing polyketide synthase (HR-PKS), a mannitol-1-phosphate dehydrogenase (MPDH), a mannitol dehydrogenase (MtDH), an arabitol dehydrogenase (ArDH) and an esterase (Est1) were found to be closely related to core biosynthesis of extracellular liamocins in Aureobasidium melanogenum 6-1-2. The HR-PKS was responsible for biosynthesis of 3,5-dihydroxydecanoic acid. The MPDH and MtDH were implicated in mannitol biosynthesis and the ArDH was involved in arabitol biosynthesis. The Est1 catalyzed ester bond formation of them. A phosphopantetheine transferase (PPTase) activated the HR-PKS and a transcriptional activator Ga11 activated expression of the PKS1 gene. Therefore, deletion of the PKS1 gene, all the three genes encoding MPDH, MtDH and ArDH, the EST1, the gene responsible for PPTase and the gene for Ga11 made all the disruptants (Δpks13, Δpta13, Δest1, Δp12 and Δg11) totally lose the ability to produce any liamocins. A GLTP gene encoding a glycolipid transporter and a MDR1 gene encoding an ABC transporter took part in transport and secretion of the produced liamocins into medium. Removal of the GLTP gene and the MDR1 gene resulted in a Δgltp1 mutant and a Δmdr16 mutant, respectively, that lost the partial ability to secrete liamocins, but which cells were swollen and intracellular lipid accumulation was greatly enhanced. Hydrolysis of liamocins released 3,5-dihydroxydecanoic acid, mannitol, arabitol and acetic acid. We proposed a core biosynthesis pathway, regulation, transport and secretion of liamocins in A. melanogenum.
迄今为止，人们尚不清楚利亚霉素如何进行生物合成、调控、运输和分泌。本研究发现，在黑曲霉 6-1-2 中，一个高度还原的聚酮合酶（HR-PKS）、甘露醇-1-磷酸脱氢酶（MPDH）、甘露醇脱氢酶（MtDH）、赤藓糖醇脱氢酶（ArDH）和酯酶（Est1）与细胞外利亚霉素的核心生物合成密切相关。HR-PKS 负责合成 3,5-二羟基癸酸。MPDH 和 MtDH 参与甘露醇的生物合成，ArDH 参与赤藓糖醇的生物合成。Est1 催化它们的酯键形成。一个磷酸泛酰巯基乙胺转移酶（PPTase）激活 HR-PKS，一个转录激活因子 Ga11 激活 PKS1 基因的表达。因此，敲除 PKS1 基因、编码 MPDH、MtDH 和 ArDH 的三个基因、EST1、负责 PPTase 的基因和 Ga11 基因使所有突变体（Δpks13、Δpta13、Δest1、Δp12 和 Δg11）完全丧失产生利亚霉素的能力。一个编码糖脂转运蛋白的 GLTP 基因和一个编码 ABC 转运蛋白的 MDR1 基因参与了产生的利亚霉素向培养基中的运输和分泌。敲除 GLTP 基因和 MDR1 基因分别导致 Δgltp1 突变体和 Δmdr16 突变体丧失部分分泌利亚霉素的能力，但细胞肿胀，细胞内脂质积累大大增强。利亚霉素的水解释放 3,5-二羟基癸酸、甘露醇、赤藓糖醇和乙酸。我们提出了黑曲霉中利亚霉素的核心生物合成途径、调控、运输和分泌。
