A novel synthetic pathway for tropolone ring formation via the olefin monoterpene intermediate terpinolene in cultured Cupressus lusitanica cells

作者：Fujita Koki^*; Bunyu Yasufumi; Kuroda Ken' ich; Ashitani Tatsuya; Shigeto Jun; Tsutsumi Yuji

来源：Journal of Plant Physiology, 2014, 171(8): 610-614.

DOI：10.1016/j.jplph.2013.12.016

• Biosynthesis
• Cupressus lusitanica
• Terpene
• beta-Thujaplicin
• Tropolone

beta-Thujaplicin is a wood monoterpene and tropolone compound with a unique conjugated 7-membered ring. Because of its strong antifungal and antitumor activities, beta-thujaplicin is used in several fields. The biosynthesis pathway of beta-thujaplicin has not yet been elucidated. Using Cupressus lusitanica cell cultures in a radioisotope feeding experiment, our group previously demonstrated that geranyl pyrophosphate (GPP) is the starting material of beta-thujaplicin biosynthesis. The results of our previous terpene synthase assay suggested that terpinolene is the first olefin terpenoid intermediate from GPP to beta-thujaplicin, although there was no experimental evidence of this at that time. In the present study, we fed deuterium-labeled terpinolene to cultured C. lusitanica cells to determine whether terpinolene is an intermediate metabolite of beta-thujaplicin biosynthesis. A gas chromatography-mass spectroscopy analysis of the cell extracts from labeled terpinolene cultures revealed a peak of labeled beta-thujaplicin that was not observed after treatment with non-labeled terpinolene. The identification of labeled beta-thujaplicin was also performed by mass spectrum assignment. The outcome indicated that terpinolene is indeed an intermediate metabolite of beta-thujaplicin biosynthesis. To the best of our knowledge, there has been no prior report that tropolone compounds are biosynthesized via a terpene biosynthesis system, and our results thus suggest the existence of a novel biosynthetic pathway that produces the conjugated 7-membered ring.

• 出版日期2014-5-1