Cryptomeridiol, a typical eudesmane diol, is the active principle component of the antispasmodic Proximol. Although it has been used for many years, the biosynthesis pathway of cryptomeridiol has remained blur. Among terpenoid natural products, terpenoid cyclases are responsible for cyclization and generation of hydrocarbon backbones. The cyclization is mediated by carbocationic cascades and ultimately terminated via deprotonation or nucleophilic capture. Isoprene precursors are, respectively, converted into hydrocarbons or hydroxylated backbones. A sesquiterpene cyclase in Tripterygium wilfordii (TwCS) was determined to directly catalyze (E,E)-farnesyl pyrophosphate (FPP) to unexpected eudesmane diols, primarily cryptomeridiol. The function of TwCS was characterized by a modular pathway engineering system in Saccharomyces cerevisiae. The major product determined by NMR spectroscopy turned out to be cryptomeridiol. This unprecedented production was further investigated in vitro, which verified that TwCS can directly produce eudesmane diols from FPP. Some key residues for TwCS catalysis were screened depending on the molecular model of TwCS and mutagenesis studies. As cryptomeridiol showed a small amount of volatile and medicinal properties, the biosynthesis of cryptomeridiol was reconstructed in S. cerevisiae. Optimized assays including modular pathway engineering and the CRISPR–cas9 system were successfully used to improve the yield of cryptomeridiol in the S. cerevisiae. The best engineered strain TE9 (BY4741 erg9::Δ-200-176 rox1::mut/pYX212-IDI + TwCS/p424-tHMG1) ultimately produced 19.73 mg/l cryptomeridiol in a shake flask culture.
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Cover Image
Cover Image
In this issue of the Biochemical Journal, Tong et al. report how a sesquiterpene synthase generates eudesmane-type sesquiterpene diols in Tripterygium wilfordii and which residues are important for cyclization. The cover image shows the flower of T. wilfordii and the structure of cryptomeridiol synthase. The background depicts ancient Chinese text that recorded the medicinal benefits of T. wilfordii and the engineered manipulation in yeast to enhance the production of the eudesmane diol cryptomeridiol. For further details, see pages 2713–2725. Image kindly provided by Wei Gao (Capital Medical University, Beijing).
Eudesmane-type sesquiterpene diols directly synthesized by a sesquiterpene cyclase in Tripterygium wilfordii
Yu-ru Tong, Ping Su, Hong-yu Guan, Tian-yuan Hu, Jin-long Chen, Yi-feng Zhang, Yu-jun Zhao, Lin-hui Gao, Xia-nan Zhang, Lu-qi Huang, Wei Gao; Eudesmane-type sesquiterpene diols directly synthesized by a sesquiterpene cyclase in Tripterygium wilfordii. Biochem J 14 September 2018; 475 (17): 2713–2725. doi: https://doi.org/10.1042/BCJ20180353
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