Famesyl diphosphate synthase FPPS

Another study with glandular trichomes from Ocimun basilicum, revealed that relative levels of GPPS and FPPS (famesyl diphosphate synthase) activities did not correlate with the total amount of terpenes produced nonetheless, it showed some correlation with the ratio monoterpene/sequiterpene [324]. 

Fig. 1.6 Phylogenetic tree of gymnosperm and angiosperm isoprenyl diphosphate synthase sequences. The isolated Picea ahies sequences are marked other isoprcnyl diphosphate synthases sequences are listed according to the major reaction product of the recombinant protein. Abbreviations GPP synthase, geranyl diphosphate synthase FPP synthase, famesyl diphosphate synthase and GGPP synthase, geranyl geranyl diphosphate synthase large su, large subunit of protein small su, small subunit of protein.

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. 

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. 

Famesyl diphosphate (FPP) is the starting molecule for the committed step in sesquiterpene biosynthesis, so artemisinin is synthesized from FPP via the mevalonate pathway in the cytosol (Fig. 89.15). A rational approach has enhanced artemisinin yields by the overexpression of famesyl diphosphate synthase... 

Figure 10.7 All terpenes are derived from allylic diphosphates which are polymers of repeating isopentyl units (IPP) put together by the action of prenyltransferases. In plants, IPP can be derived from the mevalonate biosynthetic pathway (a cytoplasmic pathway) or the methyl erythritol phosphate pathway (a plastidic pathway). Monoterpenes are then derived from the CIO precursor geranyl diphosphate (GPP), sesquiterpenes from the C15 precursor famesyl diphosphate (FPP), and diterpenes from the C20 precursor geranylgeranyl diphosphate (GGPP) by the action of terpene synthases or cyclases, which divert carbon into the specific branch pathways.

Figure 10.8 Famesyl diphosphate (FPP) can be cyclized in many different ways by sesquiterpene synthases giving rise to different classes of sesquiterpenes. The eremophilane class of sesquiterpenes has received considerable attention because the genes coding for the corresponding synthase enzymes were the first to be isolated. 25...

Fig. 4 Reconstruction of the carotenoids biosynthetic pathway in S. cerevisiae. Heterologous activities t-HMGl 3 hydroxy-3-methylglutaryl-coenzymeA, ctrE geranylgeranyldiphosphate synthase (from Xanthophyllomyces dendrorhous), Ctrl phytoene desaturase, ctrYB bifunctional enzyme phytoene synthase and lycopene cyclase. Endogenous yeast activities ISIS I geranylgeranyldiphosphate synthase. Metabolites IPP isopentenyl diphosphate, GPP geranyl diphosphate, FPP famesyl-diphosphate, GGPP geranylgeranyl diphosphate...

Fig. 1.4 Outline of terpenoid biosynthesis from isopentenyl diphosphate (IPP) via dimethylallyl diphosphate (DMAPP), gcranyl diphosphate (GPP), famesyl diphosphate (FPP) and geranylgcranyl diphosphate (GGPP). These reactions are catalyzed by isoprenyl diphosphate synthases and terpene synthases. The major products of the monoterpene, sesquiterpene, and diterpene pathways that constitute the oleoresm of Picea abies are listed. The general precursor IPP is derived either from the plastidial methylerythritol phosphate (MEP) pathway or the cytosolic mevalonaic pathway.

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)...

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

Squalene synthase (EC 2.5.1.21) known as a membrane-bound enzyme condenses two molecules of famesyl diphosphate (FPP) in a stable intermediate, the presqualene diphosphate (PS) which is then reduced by NAD(P)H to form squalene (S). In spite of various hypotheses concerning the binding sites and reaction centers, the catalytic machinery for the two reactions and the mechanism(s) responsible for the sterol mediated regulation of squalene synthase (SQS), have not been elucidated. Sterol auxotrophic mutant strains (1) can be used as tools for such studies. Therefore, before going to purify SQS from plant sources (2), we have undertaken the purification and comparative characterization of squalene synthase (SQS) from three yeast strains the wild-type FLIOO, the mutant strain erglOB and the recombinant strain FK5188 pMF13. 

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