01756nas a2200229   4500008004100000022001400041245012900055210006900184260000800253300001200261490000700273520096300280100002301243700002001266700001401286700002101300700002301321700001601344700001901360700002001379856012701399       2017                        eng d  a0021-882000aCyclization mechanism of phomopsene synthase: mass spectrometry based analysis of various site-specifically labeled terpenes0 aCyclization mechanism of phomopsene synthase mass spectrometry b  cMAY  a632-6380 v703 a<p>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.</p>1 aShinde, Sandip, S.1 aMinami, Atsushi1 aChen, Zhi1 aTokiwano, Tetsuo1 aToyomasu, Tomonobu1 aKato, Nobuo1 aSassa, Takeshi1 aOikawa, Hideaki  uhttps://library.ncl.res.in/content/cyclization-mechanism-phomopsene-synthase-mass-spectrometry-based-analysis-various-site