An Unusual Extender Unit Is Incorporated into the Modular Polyketide Synthase of Scopranones Biosynthesis
An Unusual Extender Unit Is Incorporated into the Modular Polyketide Synthase of Scopranones Biosynthesis
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DOI：
10.1021/acs.biochem.9b00908
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发表时间：
2019-12-17
期刊：
影响因子：
2.9
通讯作者：
Ikeda, Haruo
中科院分区：
文献类型：
--
作者：
Demachi, Ayumu;Uchida, Ryuji;Ikeda, Haruo
东莨菪碱酮是由链霉菌BYK-11038产生的新型骨形态发生蛋白抑制剂，具有两个非典型的勺状结构和一个3-呋喃酮结构。两个勺状部分连接到3-呋喃酮以前没有报道在天然产物中，它们的生物合成必须通过一个独特的途径。利用C-13标记的前体进行的饲养实验表明，东莨菪碱酮是由聚酮型生物合成中的三种乙酸酯和三种丁酸酯合成的。对Streptomyces sp. BYK-11038的基因组挖掘表明，该候选生物合成基因簇包含21个开放阅读框架（ORF），其中包括3个模块化聚酮酶（PKS; SprA，SprB，和SprC），由4个模块和一个加载模块以及18个额外的ORF（SprD到SprU）组成，跨越55 kbp的距离。框内缺失突变体的表征和与预测的扩展单元的饲养实验表明，两个基因，sprP和sprR，编码离散的3-氧代酰基-ACP脱氢酶，和一个基因，sprO，编码巴豆酰辅酶A还原酶，参与组装一个不寻常的C-8分支扩展单元，2-（2-乙基丁基）丙二酰辅酶A。此外，三个ORF，sprM，sprN和sprT，编码细胞色素P450和单加氧酶，是重要的剪裁酶后PKS修饰。SprT是通过氧化进行脱羧环收缩的必需酶，其将2-吡喃酮转化为3-呋喃酮。
Scopranones, produced by Streptomyces sp. BYK-11038, are the novel bone morphogenetic protein inhibitors characterized by atypical two scoop-like moieties and a 3-furanone moiety. Two scoop-like moieties connected to a 3-furanone have not previously been reported in natural products, and their biosynthesis must occur via a unique pathway. Feeding experiments using C-13-labeled precursors indicated that scopranones were synthesized from three acetates and three butyrates in polyketide-type biosynthesis. Genome mining of Streptomyces sp. BYK-11038 revealed that the candidate biosynthetic gene cluster contains 21 open reading frames (ORFs), including three modular polyketide synthases (PKSs; SprA, SprB, and SprC), which were composed of 4 modules with one loading module and 18 additional ORFs (SprD to SprU) spanning a distance of 55 kbp. The characterization of in-frame deletion mutants and feeding experiments with the predicted extender units indicated that two genes, sprP and sprR, encoding discrete 3-oxoacyl-ACP synthases, and a gene, sprO, encoding crotonyl-CoA reductase, were involved in assembling an unusual C-8 branched extender unit, 2-(2-ethylbutyl)malonyl-CoA. Additionally, three ORFs, sprM, sprN, and sprT, encoding cytochrome P450s and a monooxygenase, are important tailoring enzymes in post-PKS modification. SprT is an essential enzyme for decarboxylative ring contraction via oxidation, which converts the 2-pyranone to a 3-furanone.