https://scholars.lib.ntu.edu.tw/handle/123456789/593986
標題: | Mechanistic analysis of carbon-carbon bond formation by deoxypodophyllotoxin synthase | 作者: | Tang, Haoyu Wu, Min-Hao Lin, Hsiao-Yu Han, Meng-Ru Tu, Yueh-Hua Yang, Zhi-Jie Chien, Tun-Cheng NEI-LI CHAN Chang, Wei-Chen |
關鍵字: | C−C coupling; cyclization; natural product; oxygenase; reaction mechanism | 公開日期: | 4-一月-2022 | 卷: | 119 | 期: | 1 | 來源出版物: | Proceedings of the National Academy of Sciences of the United States of America | 摘要: | Deoxypodophyllotoxin contains a core of four fused rings (A to D) with three consecutive chiral centers, the last being created by the attachment of a peripheral trimethoxyphenyl ring (E) to ring C. Previous studies have suggested that the iron(II)- and 2-oxoglutarate-dependent (Fe/2OG) oxygenase, deoxypodophyllotoxin synthase (DPS), catalyzes the oxidative coupling of ring B and ring E to form ring C and complete the tetracyclic core. Despite recent efforts to deploy DPS in the preparation of deoxypodophyllotoxin analogs, the mechanism underlying the regio- and stereoselectivity of this cyclization event has not been elucidated. Herein, we report 1) two structures of DPS in complex with 2OG and (±)-yatein, 2) in vitro analysis of enzymatic reactivity with substrate analogs, and 3) model reactions addressing DPS's catalytic mechanism. The results disfavor a prior proposal of on-pathway benzylic hydroxylation. Rather, the DPS-catalyzed cyclization likely proceeds by hydrogen atom abstraction from C7', oxidation of the benzylic radical to a carbocation, Friedel-Crafts-like ring closure, and rearomatization of ring B by C6 deprotonation. This mechanism adds to the known pathways for transformation of the carbon-centered radical in Fe/2OG enzymes and suggests what types of substrate modification are likely tolerable in DPS-catalyzed production of deoxypodophyllotoxin analogs. |
URI: | https://scholars.lib.ntu.edu.tw/handle/123456789/593986 | ISSN: | 00278424 | DOI: | 10.1073/pnas.2113770119 |
顯示於: | 生物化學暨分子生物學科研究所 |
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