%0 Journal Article %J Journal of Antibiotics %D 2017 %T Cyclization mechanism of phomopsene synthase: mass spectrometry based analysis of various site-specifically labeled terpenes %A Shinde, Sandip S. %A Minami, Atsushi %A Chen, Zhi %A Tokiwano, Tetsuo %A Toyomasu, Tomonobu %A Kato, Nobuo %A Sassa, Takeshi %A Oikawa, Hideaki %X

Elucidation of the cyclization mechanism catalyzed by terpene synthases is important for the rational engineering of terpene cyclases. We developed a chemoenzymatic method for the synthesis of systematically deuterium-labeled geranylgeranyl diphosphate ( GGPP), starting from site-specifically deuterium-labeled isopentenyl diphosphates (IPPs) using IPP isomerase and three prenyltransferases. We examined the cyclization mechanism of tetracyclic diterpene phomopsene with phomopsene synthase. A detailed EI-MS analysis of phomopsene labeled at various positions allowed us to propose the structures corresponding to the most intense peaks, and thus elucidate a cyclization mechanism involving double 1,2-alkyl shifts and a 1,2-hydride shift via a dolabelladien-15-yl cation. Our study demonstrated that this newly developed method is highly sensitive and provides sufficient information for a reliable assignment of the structures of fragmented ions.

%B Journal of Antibiotics %V 70 %P 632-638 %8 MAY %G eng %N 5 %9 Article %3 Foreign %4 1.730 %R 10.1038/ja.2017.27