Xu Zhongli, Schenk Angéla, Hertweck Christian
Leibniz Institute for Natural Product Research and Infection Biology, HKI, Department of Biomolecular Chemistry, Beutenbergstrasse 11a, 07745 Jena, Germany.
J Am Chem Soc. 2007 May 9;129(18):6022-30. doi: 10.1021/ja069045b. Epub 2007 Apr 17.
The entire gene locus encoding the biosynthesis of the potent glutathione-S-transferase inhibitors and apoptosis inducers benastatin A and B has been cloned and sequenced. The cluster identity was unequivocally proven by deletion of flanking regions and heterologous expression in S. albus and S. lividans. Inactivation and complementation experiments revealed that a KSIII component (BenQ) similar to FabH is crucial for providing and selecting the rare hexanoate PKS starter unit. In the absence of BenQ, several novel penta- and hexacyclic benastatin derivatives with antiproliferative activities are formed. In total, five new compounds were isolated and fully characterized, and the chemical analysis was confirmed by derivatization. The most intriguing observation is that the ben PKS can utilize typical straight and branched fatty acid synthase primers. If shorter straight-chain starters are utilized, the length of the polyketide backbone is increased, resulting in the formation of an extended, hexacyclic ring system reminiscent of proposed intermediates in the griseorhodin and fredericamycin pathways. Analysis and manipulation of the hybrid fatty acid polyketide pathway provides strong support for the hypothesis that the number of chain elongations is dependent on the total size of the polyketide chain that is accommodated in the PKS enzyme cavity. Our results also further substantiate the potential of metabolic engineering toward polyphenols with altered substituents and ring systems.
编码强效谷胱甘肽-S-转移酶抑制剂和凋亡诱导剂贝纳他汀A和B生物合成的整个基因座已被克隆和测序。通过缺失侧翼区域以及在白色链霉菌和变铅青链霉菌中的异源表达，明确证实了该基因簇的同一性。失活和互补实验表明，一种与FabH相似的KSIII组分（BenQ）对于提供和选择罕见的己酸聚酮合酶起始单元至关重要。在没有BenQ的情况下，会形成几种具有抗增殖活性的新型五环和六环贝纳他汀衍生物。总共分离并完全表征了五种新化合物，并通过衍生化确认了化学分析。最引人注目的观察结果是，贝纳聚酮合酶可以利用典型的直链和支链脂肪酸合酶引物。如果使用较短的直链起始物，聚酮骨架的长度会增加，导致形成一个扩展的六环系统，让人联想到灰紫红菌素和弗雷德里卡霉素途径中提出的中间体。对混合脂肪酸聚酮途径的分析和操作有力支持了以下假设：链延伸的数量取决于聚酮链在聚酮合酶酶腔中容纳的总大小。我们的结果还进一步证实了代谢工程在改变取代基和环系统的多酚方面的潜力。
