   2.5.1.69 | 2 dimethylallyl diphosphate = diphosphate + lavandulyl diphosphate |
the two dimethylallyl diphosphate molecules, both allylic diphosphates, condense via a so-called head-to-middle condensation to form the (C10) monterpene, lavandulyl diphosphate. The enzyme structure is similar to that of the bacterial cis-prenyl synthase, undecaprenyl diphosphate synthase, and contains an allylic site (S1) in which dimethylallyl diphosphate ionizes and a second site (S2) which houses the dimethylallyl diphosphate nucleophile. Both S-thiolo-dimethylallyl diphosphate and S-thiolo-isopentenyl diphosphate bind intact to S2, but are cleaved to (thio)diphosphate, in S1. His78 is essential for catalysis and is proposed to facilitate diphosphate release in S1, while the P1 phosphate in S2 abstracts a proton from the lavandulyl carbocation to form the LPP product, structure-based catalytic mechanism, overview |
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