Germacrene synthases

Pentalenene synthase fi-om Streptomyces sp. was cloned and overexpressed in Escherichia coli getting pentalenene, a known sesquiterpene site-directed mutants yielded other known sesquiterpenes, A -protoilludene and germacrene A (Seemann 1999). 

The chiral hydrocarbon germacrene D is a widely spread plant constituent and is considered to be an important intermediate in the biosynthesis of many sesquiterpenes. Schmidt et al. [19, 20] have shown that the plant Solidago canadensis generates both optical antipodes of this compound by enzymatic cyclisation of farnesyl diphosphate using two different enantiospecific synthases. As to be seen in Fig. 17.5, the enantiomeric ratio of germacrene D in Solidago canadensis can vary from individual to individual [21]. 

One year later, Schalk [89] described a process for cloning sesquiterpene synthases from patchouli plants Pogostemon cablin) and the enzyme-catalysed terpenoid production. Various sesquiterpenes can be obtained by this method, for instance patchoulol and other germacrene-type sesquiterpenes. 

CANE, D. E., TSANTRIZOS, Y. S., Aristolochene synthase. Elucidation of the cryptic germacrene A synthase activity using the anomalous substrate dihydrofamesyl diphosphate, J. Amer. Chem. Soc., 1996,118,10037-10040. 

Yoshikuni Y, Martin VJ, Ferrin TE, Keasling JD (2006) Engineering cotton (+)-delta-cadinene synthase to an altered function germacrene D-4-ol synthase. Chem Biol 13 91-98... 

Bertea, C.M., Voster, A., Verstappen, R W., Maffei, M., Beekwilder, J. and Bouwmeester, H.J. (2006) Isoprenoid biosynthesis in Artemisia annua cloning and heterologous expression of a germacrene A synthase from a glandular trichome cDNA library. Arch. Biochem. Biophys., 448, 3-12. 

Bouwmeester, H.J., Kodde, J., Verstappen, F.W., Altug, I.G., de Kraker, J.W. and Wallaart, T.E. (2002) Isolation and characterization of two germacrene A synthase cDNA clones from chicory. Plant Physiol, 129,134 44. 

ARIMURA, G., HUBER, D.P.W., BOHLMANN, J., Forest tent caterpillars Malacosoma disstrid) induce local and systemic diurnal emissions of terpenoid volatiles in hybrid poplar (Populus trichocarpa x deltoides) cDNA cloning, functional characterization, and patterns of gene expression of (-)-germacrene D synthase, PtdTPSl. Plant J., 2004,37, 603-616. 

PROSSER, 1., ALTUG, I. G., PHILLIPS, A. L., KONIG, W. A., BOUWMEESTER, H. J., BEALE, M. H., Enantiospecific (+)- and (-)-germacrene D synthases, cloned from goldenrod, reveal a functionally active variant of the universal isoprenoid-biosynthesis aspartate-rich motif. Arch. Biochem. Biophys., 2004, 432, 136-144. 

Liicker J, Bowen P, Bohhnaim J (2004) Vitis vinifera terpenoid cyclases functional identification of two sesquiterpene synthase cDNAs encoding (-r) -valencene synthase and (—) germacrene D synthase and expression of mono- and sesquiterpene synthases in grapevine fiowers and berries. Phytochem 6 2649-2659... 

Scheme 98.10 Biosynthesis route to costunolide (82) in Asteraceae compared with artemisinic acid (79) that is spontaneously transformed in artemisinin [44, 48, 49]. ADS amorphadiene synthase, GAS germacrene A synthase, GAO germacrene A oxidase...

Protonation-induced cychzation of germacrene A generates the cis-decalin skeleton of the eudesmyl cation, an intermediate in the biosynthesis of the phytoalexin capsidiol (79). The eudesmane skeleton is converted to the 5-epi-aristolochene (80) skeleton by Wagner-Meerwein rearrangements of a hydride and a methyl group (Cane 1990). Hydroxylation of 80 then produces capsidiol. The entire process of formation of epi-aristolochene from FPP is mediated by a single synthase which has been purified from tobacco (Starks et al. 1997). The intermediacy of germacrene A in the biosynthesis was demonstrated by mutation of... 

Prosser, 1., Phillips, A.L., Gittings, S. et al (2002) (+)-(10R)-germacrene A synthase from golden-rod Solidago canadensis) cDNA isolation, bacterial expression and functional analysis. Phytochemistry, 60, 691-702. 

Jiang, J., He, X., and Cane, D.E. (2006) Geosmin biosynthesis. Streptomyces coelicolor germacradienol/germacrene D synthase converts famesyl diphosphate to geosmin./. Am. Chem. Soc., 128, 8128-8129. 

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