A novel prenyltransferase from Paracoccus denitrificans.

A new polyprenyltransferase catalysing the formation of Z-double bonds was found and partially purified from extracts of Paracoccus denitrificans. The enzyme catalysed a consecutive condensation of isopentenyl diphosphate with EE-farnesyl diphosphate as a primer to produce EE-farnesyl-all-Z-hexaprenyl diphosphate (ZE-mixed nonaprenyl diphosphate) as the final product. Not only EE-farnesyl diphosphate but also neryl diphosphate, ZE-farnesyl diphosphate, ZEE-geranylgeranyl diphosphate and ZZEE-pentaprenyl diphosphate were all accepted as substrates. This polyprenyltransferase required detergent such as Triton X-100 for its catalytic activity. The formation of ZE-mixed undecaprenyl diphosphate, which is well known as the precursor of the bacterial sugar-carrier lipid, was not detected in extracts of this bacterium.     

Purification of solanesyl-diphosphate synthase from Micrococcus luteus. A new class of prenyltransferase.

The activity of solanesyl-diphosphate synthase from Micrococcus luteus is stimulated by a high molecular mass fraction (HMF) which is separated from cell-free extracts of the same bacterium by DEAE-Toyopearl chromatography followed by Sephadex G-100 chromatography. By employing HMF in the assay procedure, solanesyl-diphosphate synthase was able to be purified to homogeneity and was found to be a homodimer with a monomeric molecular mass of 34 kDa. In contrast to hexaprenyl- and heptaprenyl-diphosphate synthases, which are composed of two easily dissociable components that are inactive unless combined, the homogeneously purified solanesyl-diphosphate synthase itself showed a catalytic activity, though weak, catalyzing the synthesis of both (all-E)-nonaprenyl-(solanesyl-) and (all-E)-octaprenyl diphosphate. HMF does not affect the stability of solanesyl-diphosphate synthase or Km values for isopentenyl diphosphate and farnesyl diphosphate, but it markedly increases Vmax values in a time-dependent manner. Several lines of evidence indicate that HMF contains a factor which binds to polyprenyl products and removes them out of the active site of enzyme to facilitate and maintain the turnover of catalysis.     

The Escherichia coli homologue of yeast RER2, a key enzyme of dolichol synthesis, is essential for carrier lipid formation in bacterial cell wall synthesis

We found in the Escherichia coli genome sequence a homologue of RER2, a Saccharomyces cerevisiae gene required for proper localization of an endoplasmic reticulum protein, and designated it rth (RER2 homologue). The disruption of this gene was lethal for E. coli. To reveal its biological function, we isolated temperature-sensitive mutants of the rth gene. The mutant cells became swollen and burst at the nonpermissive temperature, indicating that their cell wall integrity was defective. Further analysis showed that the mutant cells were deficient in the activity of cis-prenyltransferase, namely, undecaprenyl diphosphate synthase, a key enzyme of the carrier lipid formation of peptidoglycan synthesis. The cellular level of undecaprenyl phosphate was in fact markedly decreased in the mutants. These results are consistent with the fact that the Rer2 homologue of Micrococcus luteus shows undecaprenyl diphosphate synthase activity (N. Shimizu, T. Koyama, and K. Ogura, J. Biol. Chem. 273:19476-19481, 1998) and demonstrate that E. coli Rth is indeed responsible for the maintenance of cell wall rigidity. Our work on the yeast rer2 mutants shows that they are defective in the activity of cis-prenyltransferase, namely, dehydrodolichyl diphosphate synthase, a key enzyme of dolichol synthesis. Taking these data together, we conclude that the RER2 gene family encodes cis-prenyltransferase, which plays an essential role in cell wall biosynthesis in bacteria and in dolichol synthesis in eukaryotic cells and has been well conserved during evolution.     

Activation of brain phenylethanolamine-N-methyltransferase by Triton-X-100: Time related differences in the enzyme activation

The effect of different concentrations of Triton-X-100 (0.2 to 5 %) on the activity of enzyme phenylethanolamine-N-methyltransferase (PNMT) in the brain and adrenal was studied. The addition of 0.2 % Triton-X-100 to the 0.9 % KCl homogenization media resulted in 180 % activation of the brain PNMT. The similar content of this detergent added to the adrenal PNMT preparation had no marked effect on enzyme activity. Rising Triton-X-100 concentrations from 0.2 % to 5 % resulted in higher activation of brain PNMT activity but the adrenal enzyme remained rather stable. An exposure of 15 minutes of brain PNMT preparation to Triton-X-100 was the optimal interval to evoke the maximal increase in enzyme activity. This activation of brain PNMT by Triton-X-100 was observable up to 24 hours after the addition of the detergent.     

Phytoene synthase from tomato (Lycopersicon esculentum) chloroplasts – partial purification and biochemical properties

 Phytoene synthase activity in tomato chloroplasts is membrane-associated, requiring treatment with high ionic strength buffer or mild non-ionic detergent for solubilisation. Using a combination of ammonium sulphate precipitation, cation and anion exchange, dye-ligand and hydrophobic interaction chromatography, phytoene synthase has been purified 600-fold from tomato (Lycopersicon esculentum Mill.) chloroplasts. The native molecular mass of the enzyme was 43 kDa, with an isoelectric point of 4.6. Although phytoene synthase was functional in a monomeric state, under optimal native conditions it was associated with a large (at least 200 kDa) protein complex which contained other terpenoid enzymes such as isopentenyl diphosphate isomerase and geranylgeranyl diphosphate (GGPP) synthase. Both Mn²⁺ and ATP, in combination, were essential for catalytic activity; their effect was stochiometric from 0.5 to 2 mM, with K _m values for Mn²⁺, ATP and the substrate GGPP of 0.4 mM, 2.0 mM and 5 μM, respectively. The detergents Tween 60 and Triton X-100 (0.1 w/v) stimulated (5-fold) enzyme activity, but lipids (crude chloroplast lipids and phospholipids) had no such effect and could not compensate for the absence of detergent. A number of metabolites with possible regulatory effects were investigated, including β-carotene, which reduced enzyme activity in vitro some 2-fold. A comparison of phytoene synthase activity from partially purified chloroplast and chromoplast preparations indicated biochemical differences. Received: 20 January 2000 / Accepted: 16 February 2000     

Refolding and characterization of a yeast dehydrodolichyl diphosphate synthase overexpressed in Escherichia coli.

Dehydrodolichyl diphosphate synthase (DDPPs) catalyzes the sequential condensation of isopentenyl diphosphate with farnesyl diphosphate to synthesize long-chain dehydrodolichyl diphosphate, which serves as a precursor of glycosyl carrier in glycoprotein biosynthesis in eukaryotes. To perform kinetic and structural studies of DDPPs, we have expressed yeast DDPPs using Escherichia coli as the host cell. Thioredoxin and His tag were utilized to increase the solubility of the recombinant protein and facilitate its purification using Ni-nitrilotriacetic acid (NTA) column. The protein was overexpressed in E. coli but mostly existed in pellet in the absence of detergent. The low quantity of soluble DDPPs was purified using Ni-NTA, Mono Q anion-exchange, and size-column chromatographies. The protein in the pellet was solubilized with 7 M urea and purified using Ni-NTA under denaturing condition. The protein refolding was achieved via the stepwise dialysis to remove the denaturant in the presence of 6 mM beta-mercaptoethanol. Detergent n-octyl-beta-d-glucopyranoside and Triton X-100 increased the solubility of the DDPPs so that refolding can be performed at higher protein concentration. Alternatively, on-column refolding was carried out in a single step to obtain the active protein in large quantities. beta-Mercaptoethanol and Triton were both required in this quick refolding process. The kinetic studies indicated that the soluble and refolded DDPPs have comparable activities (k(cat) = 2 x 10(-4) s(-1)). Unlike its bacterial homologue, undecaprenyl diphosphate synthase, yeast DDPPs activity was not enhanced by Triton.     

Insight into the activation mechanism of Escherichia coli octaprenyl pyrophosphate synthase derived from pre-steady-state kinetic analysis

Octaprenyl pyrophosphate synthase (OPPs) catalyzes the sequential condensation of five molecules of isopentenyl pyrophosphate with farnesyl pyrophosphate to generate all-trans C40-octaprenyl pyrophosphate, which constitutes the side chain of ubiquinone. Due to the slow product release, a long-chain polyprenyl pyrophosphate synthase often requires detergent or another factor for optimal activity. Our previous studies in examining the activity enhancement of Escherichia coli undecaprenyl pyrophosphate synthase have demonstrated a switch of the rate-determining step from product release to isopentenyl pyrophosphate (IPP) condensation reaction in the presence of Triton [12]. In order to understand the mechanism of enzyme activation for E. coli OPPs, a single-turnover reaction was performed and the measured IPP condensation rate (2 s(-1)) was 100 times larger than the steady-state rate (0.02 s(-1)). The high molecular weight fractions and Triton could accelerate the steady-state rate by 3-fold (0.06 s(-1)) but insufficient to cause full activation (100-fold). A burst product formation was observed in enzyme multiple turnovers indicating a slow product release.     

Molecular analysis of prenyl chain elongating enzymes

Multiple alignments of primary structures of many kinds of prenyltransferases that participate in the most fundamental prenyl-chain backbone synthesizing process in isoprenoid biosynthesis showed seven conserved regions in the primary structures of (E)-prenyl diphosphate synthases. However, no information has been available about the structures of (Z)-prenyl diphosphate synthases until our recent isolation of the gene for the undecaprenyl diphosphate synthase of Micrococcus luteus B-P 26. The amino acid sequence of the (Z)-prenyl diphosphate synthase is totally different from those of (E)-prenyl chain elongating enzymes. Protein data base searches for sequences similar to that of the undecaprenyl diphosphate synthase yielded many unknown proteins which have not yet been characterized. Two of the proteins have recently been identified as the undecaprenyl diphosphate synthase of Escherichia coli and the dehydrodolichyl diphosphate synthase of Saccharomyces cerevisiae, indicating that there are three highly conserved regions in the primary structure of (Z)-prenyl chain elongating enzymes.     

Disruption of the structural gene for farnesyl diphosphate synthase in Escherichia coli

The chromosomal ispA gene encoding farnesyl diphosphate synthase of Escherichia coli was disrupted by inserting a neo gene cassette. The null ispA mutants were viable. The growth yield of the mutants was 70% to 80% of that of the wild-type strain under aerobic conditions, and was almost the same as the wild-type under anaerobic conditions. The levels of ubiquinone-8 and menaquinone-8 were both significantly lower (less than 13% and 18% of normal, respectively) in the mutants than in the wild-type. The undecaprenyl phosphate level in the mutants was modestly lower (40% to 70% of normal) than in the wild-type strain. Thus the synthesis of all-E-octaprenyl diphosphate, the precursor of ubiquinone-8 and menaquinone-8, was decreased more severely than that of Z,E-mixed undecaprenyl diphosphate, the precursor of undecaprenyl monophosphates, under the conditions where the synthesis of farnesyl diphosphate was decreased. The condensation of isopentenyl diphosphate with dimethylallyl diphosphate was detected in the cell-free extracts of the mutants, although it was 5% of that in the wild-type strain. A low level of farnesyl diphosphate seems to be synthesized in the mutants by other prenyltransferases such as octaprenyl diphosphate synthase or undecaprenyl diphosphate synthase.     

CDP-diacylglycerol synthase activity in Clostridium perfringens

CTP:phosphatidate cytidylyltransferase (CDP-diacylglycerol synthase; EC 2.7.7.41) was identified in the cell envelope fraction of the gram-positive anaerobe Clostridium perfringens. The association of this enzyme with the cell envelope fraction of cell extracts was demonstrated by glycerol density gradient centrifugation and by activity sedimenting with the 100,000 x g pellet. The enzyme exhibited a broad pH optimum between pH 6.5 and pH 7.5. Enzyme activity was dependent on magnesium (5 mM) or manganese (1 mM) ions. Activity was also dependent on the addition of the nonionic detergent Triton X-100 (5 mM). The apparent Km values for CTP and phosphatidic acid were 0.18 mM and 0.22 mM, respectively. Thioreactive agents inhibited activity, indicating that a sulfhydryl group is essential for activity. Maximal enzyme activity was observed at 50 degrees C.     

CDP-diacylglycerol synthase activity in Clostridium perfringens.

CTP:phosphatidate cytidylyltransferase (CDP-diacylglycerol synthase; EC 2.7.7.41) was identified in the cell envelope fraction of the gram-positive anaerobe Clostridium perfringens. The association of this enzyme with the cell envelope fraction of cell extracts was demonstrated by glycerol density gradient centrifugation and by activity sedimenting with the 100,000 x g pellet. The enzyme exhibited a broad pH optimum between pH 6.5 and pH 7.5. Enzyme activity was dependent on magnesium (5 mM) or manganese (1 mM) ions. Activity was also dependent on the addition of the nonionic detergent Triton X-100 (5 mM). The apparent Km values for CTP and phosphatidic acid were 0.18 mM and 0.22 mM, respectively. Thioreactive agents inhibited activity, indicating that a sulfhydryl group is essential for activity. Maximal enzyme activity was observed at 50 degrees C.     

The β-glucoside system of Escherichia coli III. Properties of A P–HPr: β-Glucoside phosphotransferase extracted from membranes with detergent

A P-HPr:β-glucoside phosphotransferase (enzyme II^bgl)

1 The nomenclautre of the enzymes II is that suggested by Lin (1)

has been extracted from membranes of a β-glucoside fermenting strain of Escherichia coli K 12 using the nonionic detergent Triton X–100. The extracted enzyme was rendered virtually free of both lipid and detergent by chromatography on DEAE-cellulose. At this stage, the partially purified enzyme had negligible activity, but activity was restored effectively by the addition of (1) nonionic detergents of the Tween or Triton series and (2) crude E. coli phospholipids or an anionic lipid enriched fraction, but not phosphatidylethanolamine. Detergent activators were most effective at or near the critical micelle concentration, but were inhibitory when added at concentrations above the critical micelle concentration. In order to obtain maximal initial rates of phosphotransferase activity, it was necessary to incubate the extracted, partially purified enzyme with detergent activator and HPr prior to the addition of the other assay system components. High detergent concentration inhibited the initial rate of phosphorylation by interfering with an essential step (or steps) that occur during this preliminary incubation. The activation occuring during the preliminary incubation was also highly temperature dependent; a precipitous decrease in activation was detected below 16° when Tween 40 was employed as the detergent activator. Phosphorylation mediated by the membrane associated form of the phosphotransferase was not influenced by the physical state of the lipid components of the membrane. This is in marked contrast to the properties of the phosphorylation reaction mediated by the phosphotransferase in intact cells.     

Alkali-Resistant,Alkaline Endo-l,4-β-glucanase Produced by Bacillus sp. PKM-5430

Multiple alignments of primary structures of many kinds of prenyltransferases that participate in the most fundamental prenyl-chain backbone synthesizing process in isoprenoid biosynthesis showed seven conserved regions in the primary structures of (E)-prenyl diphosphate synthases. However, no information has been available about the structures of (Z)-prenyl diphosphate synthases until our recent isolation of the gene for the undecaprenyl diphosphate synthase of Micrococcus luteus B-P 26.

The amino acid sequence of the (Z)-prenyl diphosphate synthase is totally different from those of (E)-prenyl chain elongating enzymes. Protein data base searches for sequences similar to that of the undecaprenyl diphosphate synthase yielded many unknown proteins which have not yet been characterized. Two of the proteins have recently been identified as the undecaprenyl diphosphate synthase of Escherichia coli and the dehydrodolichyl diphosphate synthase of Saccharomyces cerevisiae, indicating that there are three highly conserved regions in the primary structure of (Z)-prenyl chain elongating enzymes.     

Phosphatidylglycerophosphate synthease and phosphatidylserine synthase activites in Clostridium perfringens

Cytidine 5'-diphospho (CDP)-1,2-diacyl-sn-glycerol (CDPdiacylglycerol):sn-glycerol-3-phosphate phosphatidyltransferase (EC 2.7.8.5, phosphatidylglycero-P synthase) and CDPdiacylglycerol:L-serine O-phosphatidyltransferase (EC 2.7.8.8, phosphatidylserine synthase) activities were identified in the cell envelope fraction of the gram-positive anaerobe Clostridium perfringens. The association of phosphatidylglycero-P synthase and phosphatidylserine synthase with the cell envelope fraction of cell-free extracts was demonstrated by sucrose density gradient centrifugation, by both activities sedimenting with the 100,000 x g pellet and solubilization of both activities from the 100,000 x g pellet with Triton X-100. The pH optimum for both enzyme activities was 8.0 with tris(hydroxy-methyl)aminomethane-hydrochloride buffer. Phosphatidylglycero-P synthase activity was dependent on magnesium ions (100 mM). Phosphatidylserine synthase activity was dependent on manganese (0.1 mM) or magnesium ions (50 mM). Both enzyme activities were dependent on the addition of the nonionic detergent Triton X-100. Maximum phosphatidylglycero-P synthase and phosphatidylserine synthase activities were obtained when the molar ratio of Triton X-100 to CDP-diacylglycerol was 50:1 and 12:1, respectively. The Km for sn-glycero-3-P in the phosphatidylglycero-P synthase reaction was 0.1 mM. The Km for L-serine in the phosphatidylserine synthase reaction was 0.15 mM. Both enzyme activities were 100% stable for at least 20 min at 60 degrees C.     

Kinetic studies of Micrococcus luteus B-P 26 undecaprenyl diphosphate synthase reaction using 3-desmethyl allylic substrate analogs

In order to investigate the substrate binding feature of undecaprenyl diphosphate synthase from Micrococcus luteus B-P 26 with respect to farnesyl diphosphate and a reaction intermediate, (Z,E,E)-geranylgeranyl diphosphate, we examined the reactivity of artificial substrate analogs, 3-desmethyl farnesyl diphosphate and 3-desmethyl Z-geranylgeranyl diphosphate, which lack the methyl group at the 3-position of farnesyl diphosphate and Z-geranylgeranyl diphosphate, respectively. Undecaprenyl diphosphate synthase did not accept either of the 3-desmethyl analogs as the allylic substrate, indicating that the methyl group at the 3-position of the allylic substrate is important in the undecaprenyl diphosphate synthase reaction. These analogs showed different inhibition patterns in the cis-prenyl chain elongation reaction with respect to the reactions of farnesyl diphosphate and Z-geranylgeranyl diphosphate as allylic substrate. These results suggest that the binding site for the natural substrate farnesyl diphosphate and those for the intermediate allylic diphosphate, which contains the cis-prenyl unit, are different during the cis-prenyl chain elongation reaction.     

Purification and Characterization of Geranyl Diphosphate Synthase from Vitis vinifera L. cv Muscat de Frontignan Cell Cultures

A geranyl diphosphate synthase (EC 2.5.1.1), which catalyzes the formation of geranyl diphosphate from dimethylallyl diphosphate and isopentenyl diphosphate, was isolated from Vitis vinifera L. cv Muscat de Frontignan cell cultures. Purification of the enzyme was achieved successively by ammonium sulfate precipitation and chromatography on DEAE-Sephacel, hydroxylapatite, Mono Q, Phenyl Superose, Superose 12, and preparative nondenaturing polyacrylamide gels. The enzyme formed only geranyl diphosphate as a product. In all cases, neither neryl diphosphate, the cis isomer, nor farnesyl diphosphate was detected. The enzyme showed a native molecular mass of 68 [plus or minus] 5 kD as determined by gel permeation. On sodium dodecyl sulfate polyacrylamide gels, geranyl diphosphate synthase purified to electrophoretic homogeneity migrated with a molecular mass of 66 [plus or minus] 2 kD. Michaelis constants for isopentenyl diphosphate and dimethylallyl diphosphate were 8.5 and 56.8 [mu]M, respectively. The enzyme required Mn2+ and Mg2+ as cofactors and its activity was enhanced by Triton X-100. Inorganic pyrophosphate, aminophenylethyl diphosphate, and geranyl diphosphate had inhibitory effects on the enzyme.     

Significance of highly conserved aromatic residues in Micrococcus luteus B-P 26 undecaprenyl diphosphate synthase

Undecaprenyl diphosphate synthase catalyzes the sequential condensation of eight molecules of isopentenyl diphosphate (IPP) in the cis-configuration into farnesyl diphosphate (FPP) to produce undecaprenyl diphosphate (UPP), which is indispensable for the biosynthesis of the bacterial cell wall. This cis-type prenyltransferase exhibits a quite different mode of binding of homoallylic substrate IPP from that of trans-type prenyltransferase [Kharel Y. et al. (2001) J. Biol. Chem. 276, 28459-28464]. In order to know the IPP binding mode in more detail, we selected six highly conserved residues in Regions III, IV, and V among nine conserved aromatic residues in Micrococcus luteus B-P 26 UPP synthase for substitution by site-directed mutagenesis. The mutant enzymes were expressed and purified to homogeneity, and then their effects on substrate binding and the catalytic function were examined. All of the mutant enzymes showed moderately similar far-UV CD spectra to that of the wild-type, indicating that none of the replacement of conserved aromatic residues affected the secondary structure of the enzyme. Kinetic analysis showed that the replacement of Tyr-71 with Ser in Region III, Tyr-148 with Phe in Region IV, and Trp-210 with Ala in Region V brought about 10-1,600-fold decreases in the kcat/Km values compared to that of the wild-type but the Km values for both substrates IPP and FPP resulted in only moderate changes. Substitution of Phe-207 with Ser in Region V resulted in a 13-fold increase in the Km value for IPP and a 1,000-2,000-fold lower kcat/Km value than those of the wild-type, although the Km values for FPP showed about no significant changes. In addition, the W224A mutant as to Region V showed 6-fold and 14-fold increased Km values for IPP and FPP, respectively, and 100-250-fold decreased kcat/Km values as compared to those of the wild-type. These results suggested that these conserved aromatic residues play important roles in the binding with both substrates, IPP and FPP, as well as the catalytic function of undecaprenyl diphosphate synthase.     

Refolding and Characterization of a Yeast Dehydrodolichyl Diphosphate Synthase Overexpressed in Escherichia coli

Dehydrodolichyl diphosphate synthase (DDPPs) catalyzes the sequential condensation of isopentenyl diphosphate with farnesyl diphosphate to synthesize long-chain dehydrodolichyl diphosphate, which serves as a precursor of glycosyl carrier in glycoprotein biosynthesis in eukaryotes. To perform kinetic and structural studies of DDPPs, we have expressed yeast DDPPs using Escherichia coli as the host cell. Thioredoxin and His tag were utilized to increase the solubility of the recombinant protein and facilitate its purification using Ni-nitrilotriacetic acid (NTA) column. The protein was overexpressed in E. coli but mostly existed in pellet in the absence of detergent. The low quantity of soluble DDPPs was purified using Ni-NTA, Mono Q anion-exchange, and size-column chromatographies. The protein in the pellet was solubilized with 7 M urea and purified using Ni-NTA under denaturing condition. The protein refolding was achieved via the stepwise dialysis to remove the denaturant in the presence of 6 mM β-mercaptoethanol. Detergent n-octyl-β- -glucopyranoside and Triton X-100 increased the solubility of the DDPPs so that refolding can be performed at higher protein concentration. Alternatively, on-column refolding was carried out in a single step to obtain the active protein in large quantities. β-Mercaptoethanol and Triton were both required in this quick refolding process. The kinetic studies indicated that the soluble and refolded DDPPs have comparable activities (k_cat = 2 × 10⁻⁴ s⁻¹). Unlike its bacterial homologue, undecaprenyl diphosphate synthase, yeast DDPPs activity was not enhanced by Triton.     

Solubilization of alkyldihydroxyacetone-P synthase from Ehrlich ascites cell microsomal membranes.

The enzyme, alkyldihydroxyacetone-P synthase, has been solubilized and partially purified from microsomal preparations of Ehrlich ascites cells after treatment with Triton X-100 and phospholipase C, followed by chromatography on Sepharose 4B. When the Triton X-100 was removed after solubilization the enzyme was still active but eluted in the void volume of the Sepharose 4B column, whereas in the presence of detergent it eluted much later as a single peak of activity, indicating that the solubilized enzyme tends to aggregate unless detergent is present. The lower molecular weight form of alkyldihydroxyacetone-P synthase (in detergent) had an estimated molecular mass of 250,000–300,000 daltons.     

Bacterial phytoene synthase: molecular cloning,expression, and characterization of Erwinia herbicola phytoene synthase

Phytoene synthase (PSase) catalyzes the condensation of two molecules of geranylgeranyl diphosphate (GGPP) to give prephytoene diphosphate (PPPP) and the subsequent rearrangement of the cyclopropylcarbinyl intermediate to phytoene. These reactions constitute the first pathway specific step in carotenoid biosynthesis. The crtB gene encoding phytoene synthase was isolated from a plasmid containing the carotenoid gene cluster in Erwinia herbicola and cloned into an Escherichia coli expression system. Upon induction, recombinant phytoene synthase constituted 5-10% of total soluble protein. To facilitate purification of the recombinant enzyme, the structural gene for PSase was modified by site-directed mutagenesis to incorporate a C-terminal Glu-Glu-Phe (EEF) tripepetide to allow purification by immunoaffinity chromatography on an immobilized monoclonal anti-alpha-tubulin antibody YL1/2 column. Purified recombinant PSase-EEF gave a band at 34.5 kDa upon SDS-PAGE. Recombinant PSase-EEF was then purified to >90% homogeneity in two steps by ion-exchange and immunoaffinity chromatography. The enzyme required Mn(2+) for activity, had a pH optimum of 8.2, and was strongly stimulated by detergent. The concentration of GGPP needed for half-maximal activity was approximately 35 microM, and a significant inhibition of activity was seen at GGPP concentrations above 100 microM. The sole product of the reaction was 15,15'-Z-phytoene.