Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States.
Department of Bioengineering, Rice University, Houston, Texas 77005, United States.
J Am Chem Soc. 2023 Jul 5;145(26):14251-14259. doi: 10.1021/jacs.3c02109. Epub 2023 Jun 23.
Prenylated indole alkaloids (PIAs) possess great structural diversity and show biological activities. Despite significant efforts in investigating the biosynthetic mechanism, the key step in the transformation of 2,5-diazabicyclo[2.2.2]octane-containing PIAs into a distinct class of pentacyclic compounds remains unknown. Here, using a combination of gene deletion, heterologous expression, and biochemical characterization, we show that a unique fungal P450 enzyme CtdY catalyzes the cleavage of the amide bond in the 2,5-diazabicyclo[2.2.2]octane system, followed by a decarboxylation step to form the 6/5/5/6/6 pentacyclic ring in 21-citrinadin A. We also demonstrate the function of a subsequent cascade of stereospecific oxygenases to further modify the 6/5/5/6/6 pentacyclic intermediate to the complete 21-citrinadin A biosynthesis. Our findings reveal a key enzyme CtdY for the pathway divergence in the biosynthesis of PIAs and uncover the complex late-stage post-translational modifications in 21-citrinadin A biosynthesis.
具有重要结构多样性并表现出生物活性的prenylated indole alkaloids（PIAs）。尽管在研究生物合成机制方面做出了巨大努力，但将含有 2,5-diazabicyclo[2.2.2]octane 的 PIAs 转化为独特的 pentacyclic 化合物的关键步骤仍然未知。在这里，我们使用基因缺失、异源表达和生化表征的组合，表明一种独特的真菌 P450 酶 CtdY 催化 2,5-diazabicyclo[2.2.2]octane 系统中酰胺键的断裂，然后进行脱羧反应以在 21-citrinadin A 中形成 6/5/5/6/6 个 pentacyclic 环。我们还证明了后续一系列立体特异性加氧酶的功能，以进一步修饰 6/5/5/6/6 pentacyclic 中间体，以完成 21-citrinadin A 的生物合成。我们的发现揭示了 PIA 生物合成中途径分化的关键酶 CtdY，并揭示了 21-citrinadin A 生物合成中复杂的晚期翻译后修饰。
