Famesyl pyrophosphate synthase

Glickman, J.F. and A. Schmid. 2007. Famesyl pyrophosphate synthase real-time kinetics and inhibition by nitrogen-containing bisphosphonates in a scintillation assay. Assay Drug Dev. Technol. 5, 205-214. 

Attucci, S., Aitken, S.M., Gulick, RJ. and Ibrahim, R.K. (1995) Famesyl pyrophosphate synthase from white lupin molecular cloning, expression and purification of the expressed protein. Arch. Biochem. Biophys., 321, 493-500. 

Light, D. R., R. A. Lazarus, and M. S. Dennis, Rubber elongation by famesyl pyrophosphate synthases involves a novel switch in enzyme specificity, J. Biol. Chem., 264, 18598-18607 (1989). 

Upon the synthesis of IPP (C5) and its isomer DMAPP (C5) by either MVA or DXP pathways, the next step is chain elongation. The carbonium ion is a potent alkylating agent that can react with IPP (three molecules of IPP converted into one molecule of geranyl diphosphate (GPP) by condensation reaction catalyzed by enzyme geranyl diphosphate synthase), to yield geranyl diphosphate (GPP). Famesyl pyrophosphate synthase (EPS) is the prenyltransferase that catalyzes l -4 condensation reactions of IPP with the allylic diphosphates, dimethylallyl diphosphate (DMAPP), to produce famesyl pyrophosphate (FPP). 

Fig. 99.1 Proposed biosynthetic pathway of artemisinin in Artemisia annua L. plant. SQS Squalene synthase, ADS amorpha-4,11-diene synthase, FPP Famesyl diphosphate, FPS Famesyl pyrophosphate synthase, GPP Geranyl diphosphate, GPPS Geranyle diphosphate synthase, GS germaciene A synthase, DMAPP Dimethylallyl diphosphate, IPP isopeniraiyl diphosphate, CPS P-caryophyllene synthase, DBR2 double bond reductase 2, ECS epi-cedrol synthase, FPP fanesyl diphosphate, PS (E)-P-famesene synthase (Drawn based on informatitm published by Abdin et al., [18] and Zhang et al., 2005)...

Banyai W, Kirdmanee C, Mii M, Supaibulwatana K (2010) Overexpression of famesyl pyrophosphate synthase (EPS) gene affected artemisinin content and growth of Artemisia annua L. Plant Cell Tissue Organ 103 255-265... 

IDI, laopentanyl diphosphate Isometase IPK, laopentenyl kinase FPPS, famesyl pyrophosphate synthase GPPS, geran pyrophosphate synthase Me(abo/Ass ... 

For instance, terpene cyclases are known to catalyze the conversion of oligomeric isoprenoid pyrophosphate substrates to polycyclic hydrocarbon products. Sequence comparisons of terpene cyclases with different known specificity can allow them to be classified into monoterpene, sesquiterpene, and diterpene synthases, which utilize the 10-carbon substrate geranyl pyrophosphate, the 15-carbon substrate famesyl pyrophosphate, and the 20-carbon substrate geranyl-geranyl pyrophosphate, respectively, on the basis of sequence criteria. 

Compound 7, while not a direct biotransformation product, may have been the result of the inhibition of squalene synthase leading to the buildup of famesyl pyrophosphate, which was converted to 7 by one of the test organisms. 

Condensation of isoprenoid units then leads to the production of squalene and, ultimately, cholesterol. Both of the isoprenoid derivatives we have met so far are required. Two further condensation reactions take place. As a result, famesyl pyrophosphate, a 15-carbon compound, is produced. Two molecules of famesyl pyrophosphate condense to form squalene, a 30-carbon compound. The reaction is catalyzed by squalene synthase, and NADPH is required for the reaction. 

Fig. 5.3 Carotenoid biosynthesis in maize endosperm. Compounds IPP, isopentenyl pyrophosphate FPP, famesyl pyrophosphate GGPP, geranylgeranyl pyrophosphate DMAPP, dimethallyl pyrophosphate. Carotenoid biosynthetic pathway enzymes PSY, phytoene synthase PDS, phytoene desaturase ZDS, zetacarotene desaturase ISO, carotene isomerase LCY-B, lycopene beta cyclase LCY-E, lycopene epsilon cyclase HYD-B, beta-carotene hydroxylase HYD-E, alpha-carotene hydroxylase Isonrenoid biosynthetic pathway enzymes IPPI (IPP isomerase) GGPPS (GGPP synthase). Structures are not representative of the geometrical isomer substrates (e.g. Z-phytoene is a bent structure).

Two molecules of famesyl pyrophosphate are joined head-to-head to form squalene, a triterpene, in the first dedicated step towards sterol biosynthesis (Fig. 8.4). Squalene is then converted to 2,3-oxidosqualene, which next can be cyclized to the 30 carbon, 4-ring structure cycloartenol by the enzyme cycloartenol synthase (EC 5.4.99.8). Cycloartenol can be further modified by reactions such as desaturation or demethylation to form the common sterol backbones such as... 

The biosynthesis of rubber may be divided into three steps (1) initiation, which requires an allylic diphosphate molecule, (2) elongation, in which IPP units are added to a Z-l,4-polyisoprene chain, and (3) termination, in which the polymer is released from the rubber transferase enzyme (Cornish, 1993). In plants, the elongation of Z-l,4-polyiso-prene (natural rubber) requires a small -allylic diphosphate initiator (less than or equal to C20). Famesyl pyrophosphate (FPP) is an effective initiator of polyisoprene biosynthesis (Light et al, 1989) further, because only one molecule of FPP is needed for each molecule of rubber formed, small traces of this substance that are inadvertently present complicate biosynthetic studies. The E-allylic diphosphates are hydrophilic cytosolic compounds, whereas Z-l,4-polyisoprene is hydrophobic and compartmentalized in subcellular rubber particles. A soluble E-prenyl transferase from the latex of Hevea brasiliensis serves as a famesyl diphosphate synthase and plays no direct role in elongation of Z-l,4-polyisoprene (Cornish, 1993). Because the hydro-phobic rubber molecule is produced inside a rubber particle but is formed from hydrophilic precursors from the cytoplasm, the polymerization reaction must take place at the particle surface. 

Croteau et al., 1987). Furthermore, studies with [12,13- C 6- H]famesyl pyrophosphate as a precursor indicate that deprotonation-protonation steps to form bound ole-finic intermediates in the biosynthesis of patchoulol do not occur, providing support for a hydride shift mechanism (Croteau et al, 1987). Patchoulol synthase had a molecular weight of 80,000 and consisted of two identical subunits of 40,000. 

Geranylgeranyl pyrophosphate synthase (detected in pro-plastids of infected cells of Ricinus communis) had a molecular weight of 72,000 and required Mg (Beale and MacMillan, 1988). The enzymes with geranylgeranyl pyrophosphate synthetase activity also would accept pyrophosphates smaller than famesyl pyrophosphate, indicating that famesyl pyrophosphate probably does not lie at the branch between sterol and carotene metabolism in these organisms (Porter and Spurgeon, 1981) that is, famesyl pyrophosphate is synthesized by enzymes leading to the two series of compounds independently. 

In the biosynthesis of steroids lanosterol and cycloartenol, the building blocks DMAPP and IPP are first joined through famesyl diphosphate synthase to form geranyl pyrophosphate (GPP) and then to form FPP, presqualene pyrophosphate, squalene, and (S)-squalene-2,3-epoxide by corresponding enzymes, sequentially. The product (S)-squalene-2,3-epoxide is used to synthesize the sterols lanosterol (in animals) and cycloartenol (in plants) by lanosterol synthase and cycloartenol synthase, respectively [3]. Further, lanosterol and cycloartenol are converted into other steroids through steroidogenesis. 

In all living organisms, famesyl synthases convert isopentenyl pyrophosphate (IPP) into famesyl pyrophosphate (FPP) (77), the precursor of all sesquiterpene structures. The enzyme generating FPP, FPP synthase, has been extensively studied, and it was shown that the E,E conformation of FPP is the predominant product of famesyl synthases and generally is the substrate for sesquiterpene synthases in eukaryotes [22]. 

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