Molecular characterization of an oxidosqualene cyclase that yields shionone, a unique tetracyclic triterpene ketone of Aster tataricus

摘要

ShiononeisthemajortriterpenoidcomponentofAstertataricuspossessingauniqueallsix‐memberedtetracyclicskeletonand3‐oxo‐4‐monomethylstructure.Toclarifyitsbiosyntheticprocess,anoxidosqualenecyclasecDNAwasisolatedfromA.tataricus,andthefunctionoftheenzymewasdeterminedinlanosterolsynthase‐deficientyeast.Thecyclaseyieldedca.90%shiononeandsmallamountsofβ‐amyrin,friedelin,dammara‐20,24‐dienol,and4‐epishiononeandwasdesignatedasashiononesynthase(SHS).TranscriptsofSHSweredetectedinA.tataricusorgans,confirmingitsinvolvementinshiononebiosynthesis.SHSwasshowntohaveevolvedintheAsteraceaefromβ‐amyrinsynthaselineagesandacquiredcharacteristicspecies‐andproduct‐specificities...