Mechanism and stereochemistry of the germacradienol/germacrene D synthase of Streptomyces coelicolor A3(2).
Incubation of farnesyl diphosphate (1, FPP) with recombinant germacradienol synthase from Streptomyces coelicolor A3(2) gave, in addition to (4S,7R)-germacra-1(10)E,5E-diene-11-ol (2), 15% of (-)-germacrene D (5). Incubations of [1,1-2H2]FPP (1a), (1R)-[1-2H]FPP (1b), and (1S)-[1-2H]FPP (1c) with germacradienol/germacrene D synthase and analysis of the resulting samples of germacradienol (2) and germacrene D (5) by a combination of 1H, 2H, and 13C NMR and mass spectrometry established that it is H-1si of FPP that is lost in the formation of germacradienol (2) and that undergoes 1,3-hydride transfer in the formation of (-)-germacrene D (5). The proportion of the two products was also sensitive to isotopic labeling, with cyclization of (1S)-[1-2H]FPP (1c) giving an increased proportion (35%) of 5. These results could be explained by a mechanism involving partitioning of a common helminthogermacradienyl cation intermediate 7.
He
Xiaofei
X
Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108, USA.
Cane
David E
DE
D019883:Alkyl and Aryl Transferases / Q000737:chemistry* / Q000378:metabolism*; D003500:Cyclization; D019906:Nuclear Magnetic Resonance, Biomolecular; D011106:Polyisoprenyl Phosphates / Q000737:chemistry / Q000378:metabolism; D012717:Sesquiterpenes; D045788:Sesquiterpenes, Germacrane / Q000096:biosynthesis / Q000737:chemistry; D013237:Stereoisomerism; D013302:Streptomyces / Q000201:enzymology*
D011106:Polyisoprenyl Phosphates; D012717:Sesquiterpenes; D045788:Sesquiterpenes, Germacrane; C004808:farnesyl pyrophosphate; D019883:Alkyl and Aryl Transferases; C470416:germacrene D synthase; C027259:germacrene D