ACS Chem Biol. 2021 Jul 16;16(7):1172-1178. doi: 10.1021/acschembio.1c00365. Epub 2021 Jun 17.
Tiancimycin (TNM) A belongs to the anthraquinone-fused subfamily of enediyne natural products, and selected enediynes have been translated into clinical drugs. Previously, inactivation of in sp. CB03234 resulted in the accumulation of TNM B and TNM E, supporting the functional assignment of TnmL as a cytochrome P450 hydroxylase that catalyzes A-ring modification in TNM A biosynthesis. Herein, we report in vitro characterization of TnmL, revealing that (i) TnmL catalyzes two successive hydroxylations of TNM E, resulting in sequential production of TNM F and TNM C, (ii) TnmL shows a strict substrate preference, with the C-26 side chain playing a critical role in substrate binding, and (iii) TnmL demethylates the C-7 OCH group of TNM G, affording TNM F, thereby channeling the shunt product TNM G back into TNM A biosynthesis and representing a rare proofreading logic for natural product biosynthesis. These findings shed new insights into anthraquinone-fused enediyne biosynthesis.
天蚕霉素（TNM）A 属于蒽醌融合型烯二炔天然产物亚家族，一些选择的烯二炔已被转化为临床药物。此前，在 sp. CB03234 中失活 导致 TNM B 和 TNM E 的积累，这支持了 TnmL 作为细胞色素 P450 羟化酶的功能分配，该酶催化 TNM A 生物合成中 A 环修饰。在此，我们报告了 TnmL 的体外表征，揭示了 (i) TnmL 催化 TNM E 的两个连续羟基化，导致 TNM F 和 TNM C 的顺序产生，(ii) TnmL 表现出严格的底物偏好，C-26 侧链在底物结合中起关键作用，以及 (iii) TnmL 脱除 TNM G 的 C-7 OCH 基团，生成 TNM F，从而将分流产物 TNM G 重新引导回 TNM A 生物合成，代表了天然产物生物合成中罕见的校对逻辑。这些发现为蒽醌融合型烯二炔生物合成提供了新的见解。
