Enzymology monoterpenes

With the preceding reviews of the enzymology of monoterpene cyclization and of model studies relevant to the cyclization process, it is possible to formulate a unified stereochemical scheme for the enzymatic cyclization of geranyl pyrophosphate (Figure 4). The proposal which follows is consistent with the implications of parallel advances in related fields, most notably the contributions of Cane (8,16,24,25,52), Arigoni (67) and Coates (68,69) on the stereochemistry of sesquiterpene and diterpene cyclizations, and of Poulter and Rilling (29,70) on the stepwise, ionic mechanism of prenyl transferase, a reaction type of which several monoterpene, sesquiterpene and diterpene cyclizations are, in a sense, the intramolecular equivalents. 

Terpene synthases catalyze the first committed steps in the biosynthesis of monoterpenes, sesquiterpenes, and diterpenes. An overview is presented of the enzymology and mechanism of these terpene synthases, and their molecular cloning, expression, and sequence analysis. Detailed structural and functional evaluation of four representative monoterpene, sesquiterpene, and diterpene synthases is also presented. 

Croteau R, Cane DE (1985) Monoterpene and sesquiterpene cyclases. In Law JH, Rilling HC (eds) Methods in enzymology - steroids and isoprenoids. Academic Press, New... 

When we first undertook studies of monoterpene biosynthesis in peppermint (Mentha piperita), we and other plant biochemists were handicapped by inadequate methodology and by inadequate understanding of plants. Gas chromatography was not yet available. It was assvimed that secondary metabolites were synthesized slowly and irreversibly, so tracer experiments were conducted over periods of days instead of minutes or hours. Finally, the unique problems Of plant enzymology were not understood. 

Bxe enzymology of monoterpene biosynthesis has been extensively studied particularly in Salvia species. Systems have been obtained which mediate the formation of mono- and bicyclic monoterpenoids from geranyl pyrophosphate. Not unexpectedly the key enzyme systems are at their most active during maximum... 

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