Prenylation Prenyltransferases

Kahrel Y, Takahashi S, Yamashita S et al (2006) Manipulation of prenyl chain length determination mechanism of ci s-prenyltransferases. FEES J 273 647-657... 

Prenylation, the key step in terpene biosynthesis, is catalyzed by prenyltransferases. These enzymes are responsible for the condensation of isopentenyl pyrophosphate (IPP) with an allyl pyrophosphate, thus yielding isoprenoids. Numerous studies have been performed with fluorinated substrates in order to determine the mechanism of the reactions that involve these enzymes prenyltransferases, farnesyl diphosphate synthase (FDPSase), famesyltransferase (PFTase), and IPP isomerase. These studies are based on the potential ability of fluorine atoms to destabilize cationic intermediates, and then slow down S l type processes in these reactions. 

Prenyltransferases are a class of enzymes that transfer allylic prenyl groups to acceptor molecules. Prenyl transferases commonly refer to prenyl diphosphate synthases (even though the class of prenyl transferases also includes enzymes that catalyze the transfer of prenyl groups to acceptors that include not only isopentenyl diphosphate (IPP) but also aromatic compounds and proteins etc.). 

The reactions catalyzed by prenyltransferases are unique and interesting from a mechanistic viewpoint. The reaction starts with elimination of the diphosphate ion from an allylic diphosphate (APP) to form an allylic cation, which is attacked by the IPP molecule, with stereospecific removal of a proton to form a new C-C bond and a new double bond in the product. By repeating this type of condensation between IPP and the allylic prenyl diphosphate product, prenyltransferase can synthesize a prenyl diphosphate with a certain length and stereochemistry fixed by ifs specificify (seeFig. 10) [252]. 

The prenyl chain elongation catalyzed by prenyltransferases is quite unique because the reaction proceeds consecutively and terminates precisely at discrete chain lengths according to the specificities of the enzymes. The chain length of products varies so widely that it ranges from geraniol (CIO) to natural rubber (C > 5000). 

The formation of phytoalexins such as glyceollins and phaseollins requires C-prenylation by a range of pterocarpan prenyltransferase (PTP) activities, with dimethylallyl pyrophosphate (DMAPP) as the prenyl donor. For glyceollins and phaseollins, prenylation occurs at position C-2 or C-4 of glycinol or C-10 of 3,9-dihydroxypterocarpan. ° ° However, there are differing activities in other species. For example, in Lupinus albus (white lupin) a prenyltransferase acting at the C-6, -8, and -3 positions of isoflavones has been identified.PTPs have also been characterized in detail for the formation of prenylated flavanones in Sophora flavescens (see, e.g., Ref. 207). However, no cDNA clones for flavonoid-related prenyltransferases have been published to date. 

Fig. 5 Regio-selective prenylation of substituted indoles by novel, heterologously expressed His6-tagged prenyltransferases [71]...

DeGraw, A.J., Hast,M.A.,Xu, J., Mullen,D., Beese, L.S., Barany, G., andDistefano, M.D. (2008). Caged protein prenyltransferase substrates tools for understanding protein prenylation. Chem Biol Drug Des 72 171-181. 

Synthetic derivatives and analogs of prenyl diphosphates have historically played a key role in defining key featnres of the mechanism of enzymes that ntilize these key intermediates in the isoprenoid pathway. This has also been the case with the investigation of the protein prenyl-transferases. A brief introduction to the protein prenyltransferase enzymes is given along with outlines on the previous use of prenyl diphosphate tools and key aspects of their synthesis. The development of prenyl diphosphate-based FTase inhibitors is described. The use of prenyl diphosphate derivatives as mechanistic and structural probes is next discussed. In particular, the use of fluorinated, isotopically labeled, and photoaffinity derivatives is presented. An overview of the extensive work on the determination of FTase isoprenoid substrate specificity is then given, and the chapter concludes with a section on the development of prenyl diphosphate tools for proteomic studies. 

B. IsopRENOiD Derivatives as Chemical Tools to Interrogate Prenyltransferases and Prenyl Cyclases... 

Turek, T.C., Gaon, L, Distefano, M.D., and Strickland, C.L. (2001). Synthesis of farnesyl diphosphate analogues containing ether-linked photoactive benzophenones and their application in studies of protein prenyltransferases. J Org Chem 66 3253-3264. Turek-Etienne, T.C., Strickland, C.L., and Distefano, M.D. (2003). Biochemical and structural studies with prenyl diphosphate analogues provide insights into isoprenoid recognition by protein farnesyl transferase. Biochemistry 42 3716-3724. 

---