Structure and Function of a “Head‐to‐Middle” Prenyltransferase: Lavandulyl Diphosphate Synthase

Abstract

We report the first X-ray structure of the unique “head-to-middle” monoterpene synthase, lavandulyl diphosphate synthase (LPPS). LPPS catalyzes the condensation of two molecules of dimethylallyl diphosphate (DMAPP) to form lavandulyl diphosphate, a precursor to the fragrance lavandulol. The structure is similar to that of the bacterial cis-prenyl synthase, undecaprenyl diphosphate synthase (UPPS), and contains an allylic site (S1) in which DMAPP ionizes and a second site (S2) which houses the DMAPP nucleophile. Both S-thiolo-dimethylallyl diphosphate and S-thiolo-isopentenyl diphosphate bind intact to S2, but are cleaved to (thio)diphosphate, in S1. His78 (Asn in UPPS) 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. The results are of interest since they provide the first structure and structure-based mechanism of this unusual prenyl synthase.

Structure and Mechanism of the Monoterpene Cyclolavandulyl Diphosphate Synthase that Catalyzes Consecutive Condensation and Cyclization

“…[5] Mcl22 from Streptomyces sp.C NH-189 similarly catalyzes the "head-to-middle" condensation of DMAPP and GPP to produce C 15 sesquilavandulyl diphosphate [eq. [8] Therefore,w ee xpected that as tructural comparison between CLDS and LPPS would provide crucial information about the unique reaction of CLDS,t hus advancing the knowledge of intricate terpene synthasecatalyzed reactions. [6,7] LPPS and Mcl22, however, are unable to catalyze the subsequent cyclization reaction as CLDS does.L PPS has been biochemically characterized, and its crystal structure has been reported recently.…”

“…TwoP Pi molecules in CLDS are located at the positions of the PPi molecules at the S1 and S2 sites in LPPS. [8] In CLDS,Arg60, which corresponds to Arg127 in LPPS,c ontacts (P1)O2 in as imilar manner to Arg127 in LPPS,s uggesting that Arg60 is involved in the release and stabilization of PPi. [8] TheT ris molecule lies at the position corresponding to the space between the hydrocarbon isoprene units of two DMAPP molecules in the LPPS structure ( Figure S3b).…”

“…Based on the structure of CLDS-NH/Tris/PPi/Mg 2+ ,weconstructed adocking model bound to DMAPP ( Figure S7a) and compared this model with the DMASPP/isoprene/PPi-bound form of LPPS ( Figure S7b). [8] In this model, the distance between the C1 atom of DMAPP at S1 and the C2' atom of DMAPP at S2 is 3.1 ,w hich is likely sufficiently short for CÀCb ond formation between C1 and C2' ("head-to-middle" condensation). This idea is based on the structural basis of the similar C À Cbond formation between the C5 atom of IPP and the C1 atom of DMAPP in C 15 farnesyl diphosphate synthase (FPPS).…”

Structural and Mechanistic Insight into Terpene Synthases that Catalyze the Irregular Non‐Head‐to‐Tail Coupling of Prenyl Substrates

“…X‐ray crystallography analyses have revealed that the protein structures of UPP synthase (UPPS), LPPS, CLDS, and Mcl22 adopt a typical fold for the cis ‐type IDS family (Figure ). These structures have allowed mechanistic and structural comparison among the cis ‐type IDS homologous enzymes.…”

Head‐to‐Head Prenyl Synthases in Pathogenic Bacteria

“…There are ∼70,000 such species known [2] , produced by a wide range of terpene synthases. Isoprenoids are of general interest since they are involved in the formation of important drugs [3] ; bacterial cell wall biosynthesis [4] ; fragrances [5] ; quinones and hemes for electron transport [6] as well as the post-translational modification of proteins that are important in cellular signaling [7] .…”