KAUST Global Collaborative Research, Division of Life Science, School of Science, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
J Am Chem Soc. 2012 May 23;134(20):8625-32. doi: 10.1021/ja301735a. Epub 2012 Apr 6.
The anti-neoplastic agent didemnin B from the Caribbean tunicate Trididemnum solidum was the first marine drug to be clinically tested in humans. Because of its limited supply and its complex cyclic depsipeptide structure, considerable challenges were encountered during didemnin B's development that continue to limit aplidine (dehydrodidemnin B), which is currently being evaluated in numerous clinical trials. Herein we show that the didemnins are bacterial products produced by the marine α-proteobacteria Tistrella mobilis and Tistrella bauzanensis via a unique post-assembly line maturation process. Complete genome sequence analysis of the 6,513,401 bp T. mobilis strain KA081020-065 with its five circular replicons revealed the putative didemnin biosynthetic gene cluster (did) on the 1,126,962 bp megaplasmid pTM3. The did locus encodes a 13-module hybrid non-ribosomal peptide synthetase-polyketide synthase enzyme complex organized in a collinear arrangement for the synthesis of the fatty acylglutamine ester derivatives didemnins X and Y rather than didemnin B as first anticipated. Imaging mass spectrometry of T. mobilis bacterial colonies captured the time-dependent extracellular conversion of the didemnin X and Y precursors to didemnin B, in support of an unusual post-synthetase activation mechanism. Significantly, the discovery of the didemnin biosynthetic gene cluster may provide a long-term solution to the supply problem that presently hinders this group of marine natural products and pave the way for the genetic engineering of new didemnin congeners.
来自加勒比海被囊动物皱瘤海鞘的抗肿瘤剂 didemnin B 是第一个在人类中进行临床测试的海洋药物。由于其供应有限且其复杂的环二肽结构，在 didemnin B 的开发过程中遇到了相当大的挑战，这些挑战仍在限制 aplidine（去氢 didemnin B）的发展，aplidine 目前正在许多临床试验中进行评估。本文表明，didemnins 是海洋 α-变形菌 Tistrella mobilis 和 Tistrella bauzanensis 通过独特的组装后线成熟过程产生的细菌产物。对 6,513,401 bp 的 T. mobilis 菌株 KA081020-065 的完整基因组序列分析及其五个圆形复制子揭示了 1,126,962 bp 大片段质粒 pTM3 上的假定 didemnin 生物合成基因簇（did）。did 基因座编码一个 13 模块混合非核糖体肽合酶-聚酮合酶酶复合物，以串联排列组织，用于合成脂肪酸谷氨酰胺酯衍生物 didemnin X 和 Y，而不是最初预期的 didemnin B。T. mobilis 细菌菌落的成像质谱分析捕获了 didemnin X 和 Y 前体向 didemnin B 的时间依赖性细胞外转化，支持了一种不寻常的合成后激活机制。重要的是，didemnin 生物合成基因簇的发现可能为目前阻碍这组海洋天然产物供应的问题提供长期解决方案，并为新型 didemnin 同系物的基因工程铺平道路。
