Key Laboratory of Tropical Marine Bioresources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, China-Sri Lanka Joint Center for Education and Research, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), 1119 Haibin Road, Nansha District, Guangzhou, 511458, China.
Nat Commun. 2022 Sep 14;13(1):5386. doi: 10.1038/s41467-022-33131-0.
Xanthone-containing natural products display diverse pharmacological properties. The biosynthetic mechanisms of the xanthone formation have not been well documented. Here we show that the flavoprotein monooxygenase FlsO1 in the biosynthesis of fluostatins not only functionally compensates for the monooxygenase FlsO2 in converting prejadomycin to dehydrorabelomycin, but also unexpectedly converts prejadomycin to xanthone-containing products by catalyzing three successive oxidations including hydroxylation, epoxidation and Baeyer-Villiger oxidation. We also provide biochemical evidence to support the physiological role of FlsO1 as the benzo[b]-fluorene C5-hydrolase by using nenestatin C as a substrate mimic. Finally, we resolve the crystal structure of FlsO1 in complex with the cofactor flavin adenine dinucleotide close to the "in" conformation to enable the construction of reactive substrate-docking models to understand the basis of a single enzyme-catalyzed multiple oxidations. This study highlights a mechanistic perspective for the enzymatic xanthone formation in actinomycetes and sets an example for the versatile functions of flavoproteins.
含酮类天然产物具有多种药理活性。酮类形成的生物合成机制尚未得到很好的证明。在这里，我们表明，在 fluostatins 的生物合成中，黄素蛋白单加氧酶 FlsO1 不仅在将 prejadomycin 转化为 dehydrorabelomycin 中功能上补偿了单加氧酶 FlsO2，而且出人意料地通过催化包括羟化、环氧化和 Baeyer-Villiger 氧化在内的三个连续氧化反应，将 prejadomycin 转化为含酮类产物。我们还提供了生化证据，支持 FlsO1 作为苯并[b] -芴 C5-水解酶的生理作用，使用 nenestatin C 作为底物类似物。最后，我们解析了 FlsO1 与辅因子黄素腺嘌呤二核苷酸复合物的晶体结构，接近“in”构象，从而构建了反应性底物对接模型，以了解单酶催化的多种氧化反应的基础。这项研究突出了放线菌中酶促酮类形成的机制观点，并为黄素蛋白的多功能性树立了典范。
