Terpene cyclase, function

BACK, K. W., CHAPPELL, J., Identifying functional domains within terpene cyclases using a domain-swapping strategy, Proc. Neal. Acad. Sci. USA, 1996, 93, 6841-6845. 

Because of the striking similarities in properties, mechanisms and primary structures between the plant monoterpene, sesquiterpene, and diterpene synthases [21], the recent crystallization and X-ray diffraction analysis of 5-epi-aristolochene synthase (Nt-EAS) [62] is of central importance in providing the first three-dimensional model with which fundamental and common structural themes may be proposed. This model provides a convenient starting point for discussing general structure/function relationships of all terpene cyclases. 

The further conversion of geranyl diphosphate into monoterpenoids typically involves carbocation intermediates and multistep reaction pathways that are catalyzed by terpene cyclases. Monoterpene cyclases function by first isom-erizing geranyl diphosphate to its allylic isomer linalyl diphosphate (LPP), a process that occurs by spontaneous S>jl-like dissociation to an allylic carbocation, followed by recombination. The effect of this isomerization is to convert the C2-C3 double bond of GPP into a single bond, thereby making cyclization possible and allowing EjZ isomerization of the double bond. 

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