Ferrier Research Institute, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand.
Maurice Wilkins Centre for Molecular Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand.
J Am Chem Soc. 2023 Feb 8;145(5):2754-2758. doi: 10.1021/jacs.2c11170. Epub 2023 Jan 29.
The significant structural diversity and potent bioactivity of the fungal indole diterpenes (IDTs) has attracted considerable interest in their biosynthesis. Although substantial skeletal diversity is generated by the action of noncanonical terpene cyclases, comparatively little is known about these enzymes, particularly those involved in the generation of the subgroup containing emindole SA and DA, which show alternate terpenoid skeletons. Here, we describe the IDT biosynthetic machinery generating these unusual IDT architectures from and . The function of four putative cyclases was interrogated via heterologous expression. Two specific cyclases were identified that catalyze the formation of epimers emindole SA and DA from and , respectively. These cyclases are both clustered along with all the elements required for basic IDT biosynthesis yet catalyze an unusual Markovnikov-like cyclization cascade with alternate stereochemical control. Their identification reveals that these alternate architectures are not generated by mechanistically sloppy or promiscuous enzymes, but by cyclases capable of delivering precise regio- and stereospecificities.
真菌吲哚二萜（IDT）具有显著的结构多样性和强大的生物活性，因此其生物合成引起了广泛关注。尽管非典型萜烯环化酶的作用产生了大量的骨架多样性，但对这些酶的了解相对较少，特别是那些参与生成包含 emindole SA 和 DA 的亚组的酶，它们显示出交替的萜烯骨架。在这里，我们描述了 IDT 生物合成机制，该机制可从 和 生成这些不寻常的 IDT 结构。通过异源表达研究了四个假定环化酶的功能。鉴定出两种特定的环化酶，它们分别催化从 和 形成 emindole SA 和 DA 的对映异构体。这两种环化酶都与基本 IDT 生物合成所需的所有元件聚类在一起，但催化不寻常的 Markovnikov 样环化级联反应，具有交替的立体化学控制。它们的鉴定表明，这些交替的结构不是由机械上马虎或混杂的酶产生的，而是由能够提供精确区域和立体特异性的环化酶产生的。
