Isoprenoid Chain Elongation Research Articles

Identifying Structural Determinants of Product Specificity in Leishmania major Farnesyl Diphosphate Synthase.

Farnesyl diphosphate synthase (FPPS) is an isoprenoid chain elongation enzyme that catalyzes the sequential condensation of dimethylallyl diphosphate (C5) with isopentenyl diphosphate (IPP; C5) and the resulting geranyl diphosphate (GPP; C10) with another molecule of IPP, eventually producing farnesyl diphosphate (FPP; C15), which is a precursor for the biosynthesis of a vast majority of isoprenoids. Previous studies of FPPS have highlighted the importance of the structure around the hydrophobic chain elongation path in determining product specificity. To investigate what structural features define the final chain length of the product in FPPS from Leishmania major, we designed and expressed six mutants of LmFPPS by replacing small amino acids around the binding pocket with bulky residues. Using enzymatic assays, binding kinetics, and crystallographic studies, we analyzed the effects of these mutations on the activity and product specificity of FPPS. Our results revealed that replacement of Thr-164 with tryptophan and phenylalanine completely abolished the activity of FPPS. Intriguingly, the T164Y substitution displayed dual product specificity and produced a mixture GPP and FPP as final products, with an activity for FPP synthesis that was lower than that of the wild-type enzyme. These data indicate that Thr-164 is a potential regulator of product specificity.

Crystal structure of geranylgeranyl pyrophosphate synthase (crtE) from Nonlabens dokdonensis DSW-6

Isoprenoids comprise a diverse group of natural products with a broad range of metabolic functions. Isoprenoids are synthesized from prenyl pyrophosphates by prenyltransferases that catalyze the isoprenoid chain-elongation process to different chain lengths. We hereby present the crystal structure of geranylgeranyl pyrophosphate synthase from the marine flavobacterium Nonlabens dokdonensis DSW-6 (NdGGPPS). NdGGPPS forms a hexamer composed of homodimeric trimer, and the monomeric structure is composed of 15 α-helices (α1–α15). In this structure, we observed the binding of one pyrophosphate molecule and two glycerol molecules that mimicked substrate binding to the enzyme. The substrate binding site of NdGGPPS contains large hydrophobic residues such as Phe, His and Tyr, and structural and amino acids sequence analyses thereof suggest that the protein belongs to the short-chain prenyltransferase family.

Species differences in alternative substrate utilization by the antibacterial target undecaprenyl pyrophosphate synthase.

Undecaprenyl pyrophosphate synthase (UPPS) is a critical enzyme required for the biosynthesis of polysaccharides essential for bacterial survival. In this report, we have tested the substrate selectivity of UPPS derived from the mammalian symbiont Bacteroides fragilis, the human pathogen Vibrio vulnificus, and the typically benign but opportunistic pathogen Escherichia coli. An anthranilamide-containing substrate, 2-amideanilinogeranyl diphosphate (2AA-GPP), was an effective substrate for only the B. fragilis UPPS protein, yet replacing the amide with a nitrile [2-nitrileanilinogeranyl diphosphate (2CNA-GPP)] led to a compound that was fully functional for UPPS from all three target organisms. These fluorescent substrate analogues were also found to undergo increases in fluorescence upon isoprenoid chain elongation, and this increase in fluorescence can be utilized to monitor the activity and inhibition of UPPS in 96-well plate assays. The fluorescence of 2CNA-GPP increased by a factor of 2.5-fold upon chain elongation, while that of 2AA-GPP increased only 1.2-fold. The 2CNA-GPP compound was therefore more versatile for screening the activity of UPPS from multiple species of bacteria and underwent a larger increase in fluorescence that improved its ability to detect increases in chain length. Overall, this work describes the development of new assay methods for UPPS and demonstrates the difference in substrate utilization between forms of UPPS from different species, which has major implications for UPPS inhibitor development, assay construction, and the development of polysaccharide biosynthesis probes.

Substrate specificities of E- and Z-farnesyl diphosphate synthases with substrate analogs

Abstract Prenyltransferases catalyzes the basic isoprenoid chain elongation to produce prenyl diphosphates, which led to upward of 30,000 diverse isoprenoids as steroids, carotenoids, natural rubbers, and prenyl proteins. Here, we determined the reactivities of E- and Z-farnesyl diphosphate synthases (E- and Z-FPP synthases) isolated from Bacillus stearothermophilus and Thermobifida fusca, respectively. For this purpose we use the synthetic substrate analogs, 8-tetrahydropyran-2-yloxy-, 8-hydroxy- and 8-acetoxygeranyl diphosphates. Z-FPP synthase catalyzed the reaction between 8-hydroxygeranyl diphosphate (HOGPP) and isopentenyl diphosphate (IPP), which produced (2Z)-12-hydroxyfarnesyl diphosphate (yield: 16.7%) and (2Z, 6Z)-16-hydroxygeranylgeranyl diphosphate (yield: 6.6%). Neither E- nor Z-farnesyl diphosphate synthases detectably catalyzed reactions between 8-tetrahydropyran-2-yloxygeranyl diphosphate (8-THPOGPP) and IPP. However, a mutated E-FPP synthase (Y81S), did catalyze this reaction, producing 12-tetrahydropyran-2-yloxyfarnesyl diphosphate (12-THPOFPP) with a yield of 12.3%. Wild-type E-FPP synthase catalyzed the reaction of 8-acetoxygeranyl diphosphate (8-AcOGPP) with IPP, which produced 12-acetoxyfarnesyl diphosphate (12-AcOFPP) (yield, 21.8%). Mutant E-FPP synthase catalyzed the reaction between 8-AcOGPP with IPP, producing 12-AcOFPP and 16-acetoxygeranylgeranyl diphosphate (16-AcOGGPP) with respective yields of 55.3% and 1.7%. We believe our results contribute to a better understanding of the catalytic properties of these key enzymes and illustrate their use in the stereo-specific syntheses of compounds that may have significant biotechnological and medical applications.

Biofuels: Biomolecular Engineering Fundamentals and Advances

The biological production of fuels from renewable sources has been regarded as a feasible solution to the energy and environmental problems in the foreseeable future. Recently, the biofuel product spectrum has expanded from ethanol and fatty acid methyl esters (biodiesel) to other molecules, such as higher alcohols and alkanes, with more desirable fuel properties. In general, biosynthesis of these fuel molecules can be divided into two phases: carbon chain elongation and functional modification. In addition to natural fatty acid and isoprenoid chain elongation pathways, keto acid-based chain elongation followed by decarboxylation and reduction has been explored for higher alcohol production. Other issues such as metabolic balance, strain robustness, and industrial production process efficiency have also been addressed. These successes may provide both scientific insights into and practical applications toward the ultimate goal of sustainable fuel production.

Crystal Structure of (+)-δ-Cadinene Synthase from Gossypium arboreum and Evolutionary Divergence of Metal Binding Motifs for Catalysis

(+)-Delta-cadinene synthase (DCS) from Gossypium arboreum (tree cotton) is a sesquiterpene cyclase that catalyzes the cyclization of farnesyl diphosphate in the first committed step of the biosynthesis of gossypol, a phytoalexin that defends the plant from bacterial and fungal pathogens. Here, we report the X-ray crystal structure of unliganded DCS at 2.4 A resolution and the structure of its complex with three putative Mg(2+) ions and the substrate analogue inhibitor 2-fluorofarnesyl diphosphate (2F-FPP) at 2.75 A resolution. These structures illuminate unusual features that accommodate the trinuclear metal cluster required for substrate binding and catalysis. Like other terpenoid cyclases, DCS contains a characteristic aspartate-rich D(307)DTYD(311) motif on helix D that interacts with Mg(2+)(A) and Mg(2+)(C). However, DCS appears to be unique among terpenoid cyclases in that it does not contain the "NSE/DTE" motif on helix H that specifically chelates Mg(2+)(B), which is usually found as the signature sequence (N,D)D(L,I,V)X(S,T)XXXE (boldface indicates Mg(2+)(B) ligands). Instead, DCS contains a second aspartate-rich motif, D(451)DVAE(455), that interacts with Mg(2+)(B). In this regard, DCS is more similar to the isoprenoid chain elongation enzyme farnesyl diphosphate synthase, which also contains two aspartate-rich motifs, rather than the greater family of terpenoid cyclases. Nevertheless, the structure of the DCS-2F-FPP complex shows that the structure of the trinuclear magnesium cluster is generally similar to that of other terpenoid cyclases despite the alternative Mg(2+)(B) binding motif. Analyses of DCS mutants with alanine substitutions in the D(307)DTYD(311) and D(451)DVAE(455) segments reveal the contributions of these segments to catalysis.

Residues Around the Catalytic Pocket of DdsA Are Important for Isoprenoids Chain Elongation

Nineteen mutants of decaprenyl diphosphate synthase from Gluconobacter suboxydans were generated and their production of ubiquinones (UQs) was compared to that of the wild type protein. The accessible surface area and the polarity of amino acid around the catalytic pocket wield remarkable influences on the isoprenoid chain elongation of UQs.

Enzymatic Aspects of Isoprenoid Chain Elongation.

Enzymatic Aspects of Isoprenoid Chain Elongation.

6 イソプレノイド生合成における鎖延長機構 : 中鎖プレニル二リン酸合成酵素遺伝子のクローニングとその解析(口頭発表の部)

6 イソプレノイド生合成における鎖延長機構 : 中鎖プレニル二リン酸合成酵素遺伝子のクローニングとその解析(口頭発表の部)

Terpenoid biosynthesis and the stereochemistry of enzyme-catalysed allylic addition—elimination reactions

Allylic addition-elimination reactions are widely used in the enzyme-catalysed formation of terpenoid metabolites. It has earlier been shown that the isoprenoid chain elongation reaction catalysed by farnesyl pyrophosphate synthase involving successive condensations of dimethylallyl pyrophosphate (DMAPP) and geranyl pyrophosphate (GPP) with isopentenyl pyrophosphate (IPP) corresponds to such an SE' reaction with net syn stereochemistry for the sequential electrophilic addition and proton elimination steps. Studies of the enzymic cyclization of farnesyl pyrophosphate (FPP) to pentalenene have now established the stereochemical course of two additional biological SE' reactions. Incubation of both (9R)- and (9S)-[9-3H,4,8-14]FPP with pentalenene synthase and analysis of the resulting labelled pentalenene has revealed that H-9re of FPP becomes H-8 of pentalenene, while H-9si undergoes net intramolecular transfer to the adjacent carbon, becoming H-1re (H-1 alpha) of pentalenene, as confirmed by subsequent experiments with [10-2H, 11-13C]FPP. These results correspond to net anti-stereochemistry in the intramolecular allylic addition-elimination reaction. The stereochemical course of a second SE' reaction has now been examined by analogous incubations of (4S,8S)-[4,8-3H,4,8-14C]FPP and (4R,8R)-[4,8-3H, 4.8-14C]FPP with pentalenene synthase. Determination of the distribution of label in the derived pentalenenes showed stereospecific loss of the original H-8si proton. Analysis of the plausible conformation of the presumed reaction intermediates revealed that the stereochemical course of the latter reaction cannot properly be described as either syn or anti, since cyclization and subsequent double bond formation require significant internal motions to allow proper overlap of the scissile C-H bond with the developing carbocation.

イソプレノイド鎖延長酵素の機能

イソプレノイド鎖延長酵素の機能