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PubMed2004

Coordinated gene expression for pheromone biosynthesis in the pine engraver beetle, Ips pini (Coleoptera: Scolytidae).

In several pine bark beetle species, phloem feeding induces aggregation pheromone production to coordinate a mass attack on the host tree. Male pine engraver beetles, Ips pini (Say) (Coleoptera: Scolytidae), produce the monoterpenoid pheromone component ipsdienol de novo via the mevalonate pathway in the anterior midgut upon feeding. To understand how pheromone production is regulated in this tissue, we used quantitative real-time PCR to examine feeding-induced changes in gene expression of seven mevalonate pathway genes: acetoacetyl-coenzyme A thiolase, 3-hydroxy-3-methylglutaryl coenzyme A synthase, 3-hydroxy-3-methylglutaryl coenzyme A reductase, mevalonate 5-diphosphate decarboxylase, isopentenyl-diphosphate isomerase, geranyl-diphosphate synthase (GPPS), and farnesyl-diphosphate synthase (FPPS). In males, expression of all these genes significantly increased upon feeding. In females, the expression of the early mevalonate pathway genes (up to and including the isomerase) increased significantly, but the expression of the later genes (GPPS and FPPS) was unaffected or decreased upon feeding. Thus, feeding coordinately regulates expression of the mevalonate pathway genes necessary for pheromone biosynthesis in male, but not female, midguts. Furthermore, basal mRNA levels were 5- to 41-fold more abundant in male midguts compared to female midguts. This is the first report of coordinated regulation of mevalonate pathway genes in an invertebrate model consistent with their sex-specific role in de novo pheromone biosynthesis.

Animals↗
PubMed1991

Human liver alcohol dehydrogenases catalyze the oxidation of the intermediary alcohols of the shunt pathway of mevalonate metabolism.

Human liver alcohol dehydrogenase (ADH) catalyzes the oxidation of 3,3-dimethylallyl alcohol, the intermediary alcohol of the shunt pathway of mevalonate metabolism. ADH isozymes differ in their activities toward this alcohol in the order gamma 1 gamma 1 greater than gamma 2 gamma 2 approximately alfa alfa greater pi pi approximately beta 2 beta 2 approximately beta 1 beta 1 much greater than chi chi; kcat/Km values are 1.4 x 10(8), 1.9 x 10(7), 1.4 x 10(7), 5.6 x 10(6), 3.6 x 10(6), 1.6 x 10(6) and 2.5 x 10(3) M-1 min-1, respectively. The intermediary alcohols geraniol and farnesol of the proposed branch pathways of mevalonate metabolism are also oxidized by these isozymes with similar relative efficiencies. The genetic determinants of ADH isozymes may contribute to the observed differences in serum cholesterol levels among and within various populations.

1-Propanol↗
PubMed2004

[Statins as possible therapeutic tools for osteoporosis].

Statins are cholesterol-lowering drugs as they inhibit HMG-CoA reductase, which is a rate limiting enzyme in the mevalonate pathway. Recently, mevalonate metabolites are also shown to play pivotal roles in the regulation of generation and function of osteoclasts and osteoblasts. However, there have been great controversies in effects of statins on bone metabolism, especially that on osteoporotic fractures in human. Here we briefly review the role of statins in bone metabolism through the survey of clinical observations.

Animals↗
PubMed1997

Endotoxin, tumor necrosis factor, and interleukin-1 decrease hepatic squalene synthase activity, protein, and mRNA levels in Syrian hamsters.

Recent studies have shown that endotoxin (LPS) administration to Syrian hamsters markedly increased hepatic HMG-CoA reductase activity, protein mass, and mRNA levels, but only produced a modest increase in hepatic cholesterol synthesis, suggesting that LPS may also influence other key enzymes involved in the regulation of cholesterol metabolism. In the present study, we have examined the effect of LPS and cytokines on the activity, protein mass, and mRNA level of squalene synthase, which is the first committed enzyme in cholesterol biosynthesis and is located at a branch point in the mevalonate pathway. Our results demonstrate that LPS administration produces a marked decrease in the mRNA levels of squalene synthase. This decrease in squalene synthase mRNA occurred very rapidly (90 min after LPS) and required relatively small doses of LPS (1 microg/100 gm body weight). LPS also significantly decreased squalene synthase activity and protein mass. Finally, LPS produced a marked decrease in squalene synthase mRNA, activity, and protein levels when the basal levels of squalene synthase expression were increased 4-fold by prior treatment with bile acid binding resin, colestipol. Tumor necrosis factor and interleukin-1, which mediate many of the metabolic effects of LPS, also decreased hepatic squalene synthase activity and mRNA levels. Taken together, our results suggest that the discordant regulation of HMG-CoA reductase and squalene synthase during the host response to infection and inflammation may have substantial effects on the regulation of substrate flux into the non-sterol pathways of mevalonate metabolism.

Animals↗
PubMed2000

The regulation of activity of main mevalonic acid pathway enzymes: farnesyl diphosphate synthase, 3-hydroxy-3-methylglutaryl-CoA reductase, and squalene synthase in yeast Saccharomyces cerevisiae.

The co-regulation of the main mevalonic acid pathway enzymes was investigated in the yeast Saccharomyces cerevisiae. It was found that a 6-fold increase in FPPS activity compared with that of the wild-type strain FL100 did not cause significant changes in HMG-CoA reductase activity, while the amounts of synthesized dolichols and ergosterol increased by 80 and 32%, respectively. The disruption of the SQS gene in the strain grown in the presence of ergosterol repressed the activities of both FPP synthase and HMG-CoA reductase to a comparable degree, whereas in the same strain starved for ergosterol the activity of FPPS was 10-fold higher and HMG-CoA reductase activity was practically unchanged. We show that FPPS is the enzyme that regulates the flow rate of synthesized mevalonic acid pathway products independent of HMG-CoA reductase and SQS.

Alkyl and Aryl Transferases↗
PubMed1994

Regulated degradation of HMG-CoA reductase, an integral membrane protein of the endoplasmic reticulum, in yeast.

Numerous integral membrane proteins are degraded in the mammalian ER. HMG-CoA reductase (HMG-R), a key enzyme in the mevalonate pathway by which isoprenoids and sterols are synthesized, is one substrate of ER degradation. The degradation of HMG-R is modulated by feedback signals from the mevalonate pathway. We investigated the role of regulated degradation of the two isozymes of HMG-R, Hmg1p and Hmg2p, in the physiology of Saccharomyces cerevisiae. Hmg1p was quite stable, whereas Hmg2p was rapidly degraded. Degradation of Hmg2p proceeded independently of vacuolar proteases or secretory traffic, indicating that Hmg2p degradation occurred at the ER. Hmg2p stability was strongly affected by modulation of the mevalonate pathway through pharmacological or genetic means. Decreased mevalonate pathway flux resulted in decreased degradation of Hmg2p. One signal for degradation of Hmg2p was a nonsterol, mevalonate-derived molecule produced before the synthesis of squalene. Genetic evidence indicated that a farnesylated protein may also be necessary for Hmg2p degradation. Studies with reporter genes demonstrated that the stability of each isozyme was determined by its noncatalytic NH2-terminal domain. Our data show that ER protein degradation is widely conserved among eukaryotes, and that feedback control of HMG-R degradation is an ancient paradigm of regulation.

Endopeptidases↗
PubMed2005

4,8-Dimethyldecanal, the aggregation pheromone of Tribolium castaneum, is biosynthesized through the fatty acid pathway.

4,8-Dimethyldecanal (4,8-DMD) is the aggregation pheromone produced by male red flour beetles (RFB), Tribolium castaneum. To elucidate the biosynthetic origin of 4,8-DMD, the following studies were performed: (1) effects of juvenile hormone (JH) III, and pathway inhibitors mevastatin, an inhibitor of the mevalonate pathway, and 2-octynoic acid, an inhibitor of the fatty acid pathway, were tested to determine whether 4,8-DMD is derived from the fatty acid pathway or the mevalonate pathway; (2) incorporation of 13C-labeled acetate, propionate, and mevalonolactone into 4,8-DMD was measured to directly determine the biosynthetic origin of 4,8-DMD; and (3) incorporation of deuterium-labeled precursors, including 2-methylbutanoate (C5D), 4-methylhexanoate (C7D), 2,6-dimethyloctanoate (C10D), and 4,8-dimethyldecanoate (C12D) was tested to determine whether 4,8-DMD is biosynthesized in the sequence Ac-Pr-Ac-Pr-Ac (Ac; acetate, Pr; propionate). JH III was topically applied to males at various doses. Inhibitors and isotopically labeled substrates were administered orally by feeding the beetles flour treated with the substrates of interest, after which volatiles were collected from both sexes of RFBs. The amount of 4,8-DMD produced was significantly reduced with increasing doses of JH III. Also, 2-octynoic acid inhibited the production of 4,8-DMD, but mevastatin did not. Exposure of RFBs to [1-(13)C]acetate and [1-(13)C]propionate, but not [2-(13)C]mevalonolactone, resulted in incorporation of the labeled compounds into 4,8-DMD. RFBs fed flour treated with deuterium-labeled C5D, C10D, and C12D, but not C7D, incorporated these compounds into 4,8-DMD. The findings that the production of 4,8-DMD was inhibited by 2-octynoic acid but unaffected by mevastatin, combined with the high incorporation of [1-(13)C]acetate and [1-(13)C]propionate into 4,8-DMD and the incorporation of deuterated precursors, unambiguously demonstrated that 4,8-DMD is of fatty acid rather than terpene biosynthetic origin, and that the biosynthesis of 4,8-DMD proceeds in the sequence Ac-Pr-Ac-Pr-Ac.

Acetates↗
PubMed1999

The role of geranylgeranylation in bone resorption and its suppression by bisphosphonates in fetal bone explants in vitro: A clue to the mechanism of action of nitrogen-containing bisphosphonates.

Bisphosphonates, synthetic compounds used in the treatment of skeletal disorders, suppress osteoclast-mediated bone resorption by a yet unidentified mechanism. Previous studies showed that some bisphosphonates can inhibit enzymes of the mevalonate pathway, and nitrogen-containing bisphosphonates inhibit protein prenylation in mouse macrophages. In the present study, we examined the involvement of the mevalonate pathway in basal and bisphosphonate-inhibited osteoclastic resorption in fetal mouse long bone explants, an experimental model representative of the in vivo action of bisphosphonates. Mevastatin inhibited bone resorption at concentrations similar to those of the potent bisphosphonate ibandronate. This effect could be totally reversed by the addition of mevalnate and geranylgeraniol but not farnesol. The first two intermediates but not the latter could also stimulate basal bone resorption. The inhibitory effect of ibandronate on bone resorption could be totally reversed by the addition of geranylgeraniol and to a small extent only by mevalonate and farnesol, indicating that the bisphosphonate acts at a level of the mevalonate pathway different from that of mevastatin. Histologic sections of ibandronate-treated bone explants showed further rescue of functioning osteoclasts during concomitant treatment with geranylgeraniol. Finally, the reversibility of bisphosphonate inhibited osteoclastic resorption by geranylgeraniol was also demonstrated for the potent nitrogen-containing bisphosphonates alendronate, olpadronate, and risedronate but not for the non-nitrogen-containing bisphosphonates clodronate and etidronate. These studies demonstrate that protein geranylgeranylation but not farnesylation is important for osteoclast-mediated bone resorption and that nitrogen-containing bisphosphonates exert their antiresorptive action probably by affecting enzymes of the mevalonate pathway involved in the generation of geranylgeranyl pyrophosphate.

Animals↗
PubMed1990

Plastidic Isoprenoid Synthesis during Chloroplast Development : Change from Metabolic Autonomy to a Division-of-Labor Stage.

The chloroplast isoprenoid synthesis of very young leaves is supplied by the plastidic CO(2) --> pyruvate --> acetyl-coenzyme A (C(3) --> C(2)) metabolism (D Schulze-Siebert, G Schultz [1987] Plant Physiol 84: 1233-1237) and occurs via the plastidic mevalonate pathway. The plastidic C(3) --> C(2) metabolism and/or plastidic mevalonate pathway of barley (Hordeum vulgare L.) seedlings changes from maximal activity at the leaf base (containing developing chloroplasts with incomplete thylakoid stacking but a considerable rate of photosynthetic CO(2)-fixation) almost to ineffectivity at the leaf tip (containing mature chloroplasts with maximal photosynthetic activity). The ability to import isopentenyl diphosphate from the extraplastidic space gradually increases to substitute for the loss of endogenous intermediate supply for chloroplast isoprenoid synthesis (change from autonomic to division-of-labor stage). Fatty acid synthesis from NaH(14)CO(3) decreases in the same manner as shown for leaf sections and chloroplasts isolated from these. Evidence has been obtained for a drastic decrease of pyruvate decarboxylase-dehydrogenase activity during chloroplast development compared with other anabolic chloroplast pathways (synthesis of aromatic amino acid and branched chain amino acids). The noncompetition of pyruvate and acetate in isotopic dilution studies indicates that both a pyruvate-derived and an acetate-derived compound are simultaneously needed to form introductory intermediates of the mevalonate pathway, presumably acetoacetyl-coenzyme A.

Journal Article↗
PubMed2001

Blocking protein geranylgeranylation is essential for lovastatin-induced apoptosis of human acute myeloid leukemia cells.

Lovastatin is an inhibitor of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the major regulatory enzyme of the mevalonate pathway. We have previously reported that lovastatin induces a significant apoptotic response in human acute myeloid leukemia (AML) cells. To identify the critical biochemical mechanism(s) essential for lovastatin-induced apoptosis, add-back experiments were conducted to determine which downstream product(s) of the mevalonate pathway could suppress this apoptotic response. Apoptosis induced by lovastatin was abrogated by mevalonate (MVA) and geranylgeranyl pyrophosphate (GGPP), and was partially inhibited by farnesyl pyrophosphate (FPP). Other products of the mevalonate pathway including cholesterol, squalene, lanosterol, desmosterol, dolichol, dolichol phosphate, ubiquinone, and isopentenyladenine did not affect lovastatin-induced apoptosis in AML cells. Our results suggest that inhibiting geranylgeranylation of target proteins is the predominant mechanism of lovastatin-induced apoptosis in AML cells. In support of this hypothesis, the geranylgeranyl transferase inhibitor (GGTI-298) mimicked the effect of lovastatin, whereas the farnesyl transferase inhibitor (FTI-277) was much less effective at triggering apoptosis in AML cells. Inhibition of geranylgeranylation was monitored and associated with the apoptotic response induced by lovastatin and GGTI-298 in the AML cells. We conclude that blockage of the mevalonate pathway, particularly inhibition of protein geranylgeranylation holds a critical role in the mechanism of lovastatin-induced apoptosis in AML cells.

Acute Disease↗
PubMed2002

Enterococcus faecalis 3-hydroxy-3-methylglutaryl coenzyme A synthase, an enzyme of isopentenyl diphosphate biosynthesis.

Biosynthesis of the isoprenoid precursor isopentenyl diphosphate (IPP) proceeds via two distinct pathways. Sequence comparisons and microbiological data suggest that multidrug-resistant strains of gram-positive cocci employ exclusively the mevalonate pathway for IPP biosynthesis. Bacterial mevalonate pathway enzymes therefore offer potential targets for development of active site-directed inhibitors for use as antibiotics. We used the PCR and Enterococcus faecalis genomic DNA to isolate the mvaS gene that encodes 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase, the second enzyme of the mevalonate pathway. mvaS was expressed in Escherichia coli from a pET28 vector with an attached N-terminal histidine tag. The expressed enzyme was purified by affinity chromatography on Ni(2+)-agarose to apparent homogeneity and a specific activity of 10 micromol/min/mg. Analytical ultracentrifugation showed that the enzyme is a dimer (mass, 83.9 kDa; s(20,w), 5.3). Optimal activity occurred in 2.0 mM MgCl(2) at 37(o)C. The DeltaH(a) was 6,000 cal. The pH activity profile, optimum activity at pH 9.8, yielded a pK(a) of 8.8 for a dissociating group, presumably Glu78. The stoichiometry per monomer of acetyl-CoA binding was 1.2 +/- 0.2 and that of covalent acetylation was 0.60 +/- 0.02. The K(m) for the hydrolysis of acetyl-CoA was 10 microM. Coupled conversion of acetyl-CoA to mevalonate was demonstrated by using HMG-CoA synthase and acetoacetyl-CoA thiolase/HMG-CoA reductase from E. faecalis.

Acetyl Coenzyme A↗
PubMed1995

Activity, pharmacological inhibition and biological regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase in Trypanosoma brucei.

Activity of hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase, the key enzyme in the biosynthesis of steroids and polyisoprenoids in mammalian cells, has been detected in both the bloodstream form and the culture-adapted procyclic form of Trypanosoma brucei (3.7 +/- 0.6 and 12.7 +/- 1.8 pmol mevalonate produced min-1 (mg cell protein)-1, respectively). The enzyme activity is enriched 6-fold in microsomal fractions. Several competitive inhibitors of mammalian HMG-CoA reductase, including synvinolin (simvastatin), inhibit the multiplication of both forms of trypanosome in vitro (IC50, approx. 25-50 microM after 2-3 days). This growth inhibition is potentiated by agents interfering with the exogenous supply of cholesterol, such as antibodies blocking the low-density lipoprotein (LDL) receptor, or 5 microM chloroquine. Conversely, growth inhibition by synvinolin can be largely reverted either by 300 nM LDL or by products of the mevalonate pathway, such as 20 mM mevalonate and in procyclics by 100 microM squalene or cholesterol. In procyclics, low concentrations of synvinolin selectively inhibit the incorporation of [14C]acetate into sterols, but not into fatty acids. These results argue for a critical role in trypanosomes of a mevalonate pathway, that is involved in the biosynthesis of sterol and probably of other metabolites. The HMG-CoA reductase activity is decreased 2-fold in procyclics incubated with 4 mM mevalonate and increased 2-fold in the presence of 2.5 microM synvinolin. Synvinolin also upregulates LDL binding up to 4-fold. These data suggest that HMG-CoA reductase and LDL receptor expression are regulated in T. brucei as in mammalian cells, to ensure sterol homeostasis.

Acetates↗
PubMed1990

Identification and preliminary characterization of protein-cysteine farnesyltransferase.

Ras proteins must be isoprenylated at a conserved cysteine residue near the carboxyl terminus (Cys-186 in mammalian Ras p21 proteins) in order to exert their biological activity. Previous studies indicate that an intermediate in the mevalonate pathway, most likely farnesyl pyrophosphate, is the donor of this isoprenyl group. Inhibition of mevalonate synthesis reverts the abnormal phenotypes induced by the mutant RAS2Val-19 gene in Saccharomyces cerevisiae and blocks the maturation of Xenopus oocytes induced by an oncogenic Ras p21 protein of human origin. These results have raised the possibility of using inhibitors of the mevalonate pathway to block the transforming properties of ras oncogenes. Unfortunately, mevalonate is a precursor of various end products essential to mammalian cells, such as dolichols, ubiquinones, heme A, and cholesterol. In this study, we describe an enzymatic activity(ies) capable of catalyzing the farnesylation of unprocessed Ras p21 proteins in vitro at the correct (Cys-186) residue. This farnesylating activity is heat-labile, requires Mg2+ or Mn2+ ions, is linear with time and with enzyme concentration, and is present in all mammalian cell lines and tissues tested. Gel filtration analysis of a partially purified preparation of protein farnesyltransferase revealed two peaks of activity at 250-350 kDa and 80-130 kDa. Availability of an in vitro protein farnesyltransferase assay should be useful in screening for potential inhibitors of ras oncogene function that will not interfere with other aspects of the mevalonate pathway.

Alkyl and Aryl Transferases↗
PubMed2003

The mevalonate synthesis pathway as a therapeutic target in cancer.

Farnesyl transferase inhibitors have emerged as bona fide anticancer agents whereas the development of geranylgeranyl transferase inhibitors has been mitigated by overt systemic toxicities. Evidence suggests that the therapeutic value of farnesyl transferase inhibitors is an indirect result of perturbations in the function of geranylgeranylated Rho proteins. To address this question, we used inhibitors of the mevalonate synthesis pathway to decrease cellular levels of farnesly and geranylgeranly isoprenoids and supplemented our culture systems with exogenous isoprenoids accordingly. Using a murine lung alveolar carcinoma cell line (Line 1), we report a dose-dependent inhibition of tumor cell proliferation, adhesion and invasiveness, in response to alendronate (3-30 micromol/L) and mevastatin (1-10 micromol/L). Supplementation of cultures with geranylgeranyl pyrophosphates (100 micromol/L) was observed to rescue drug-induced phenotypic changes whereas farnesyl pyrophosphate (100 micromol/L) had a minimal effect. Our observations highlight the mevalonate synthesis pathway as a target for anticancer therapies and suggest a greater role for geranylgeranylated proteins in cellular processes germane to cancer.

Acute-Phase Proteins↗
PubMed1990

Effects of simvastatin (MK-733) on branched pathway of mevalonate.

The effects of simvastatin (MK-733), a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, on the branched pathway of mevalonate metabolism were studied in Hep G2 cells. The synthesis of cholesterol, ubiquinone and dolichol were examined using various radiolabeled precursors. The effect on DNA synthesis was also determined. MK-733 at a concentration of 1 microM potently inhibited the incorporation of [3H]acetate into cholesterol (84%) without affecting that from [3H]mevalonolactone. Under these conditions, MK-733 reduced the incorporation of L-[14C]tyrosine into ubiquinone slightly (14%), although it did not suppress that from [3H] acetate. The incorporation of [3H]acetate into dolichol was slightly reduced by MK-733. On the contrary, the incorporation of [3H]mevalonolactone into ubiquinone and dolichol was increased by MK-733. This apparent increase in incorporation was thought to be largely due to the higher specific radioactivity of the intracellular pool of mevalonate. The present study demonstrated that MK-733 slightly suppressed the synthesis of ubiquinone and dolichol in Hep G2 cells. However, the extent of their reduction was far less than the effect on cholesterol synthesis, suggesting that there were differences in substrate affinity between the enzymes participating in the cholesterol synthetic pathway and those in the ubiquinone or dolichol synthetic pathway. Furthermore, MK-733 did not affect DNA synthesis even at a concentration of 10 microM.

Animals↗
PubMed2006

A new endogenous ATP analog (ApppI) inhibits the mitochondrial adenine nucleotide translocase (ANT) and is responsible for the apoptosis induced by nitrogen-containing bisphosphonates.

1. Bisphosphonates are currently the most important class of antiresorptive drugs used for the treatment of diseases with excess bone resorption. On the basis of their molecular mechanism of action, bisphosphonates can be divided into two pharmacological classes; nitrogen-containing (N-BPs) and non-nitrogen-containing bisphosphonates (non-N-BP). Both classes induce apoptosis but they evoke it differently; N-BPs by inhibiting the intracellular mevalonate pathway and protein isoprenylation, and non-N-BPs via cytotoxic ATP analog-type metabolites. N-BPs are not metabolized to ATP analogs, but we report here that these bisphosphonates can induce formation of a novel ATP analog (ApppI) as a consequence of the inhibition of the mevalonate pathway in cells. We also investigated whether ApppI is involved in the apoptosis induced by N-BPs. 2. Mass spectrometry and NMR were used to identify ApppI in N-BP treated osteoclasts, macrophages and glioma cells. The potency of different bisphosphonates to promote ApppI production was tested in J774 macrophages. The effects of ApppI on ADP/ATP translocase in isolated mitochondria and its capability to induce apoptosis in osteoclasts were also studied. 3. ApppI production correlated well with the capacity of N-BPs to inhibit mevalonate pathway. ApppI inhibited the mitochondrial ADP/ATP translocase and caused apoptosis in osteoclasts. 4. In conclusion, these findings provide the basis for a new mechanism of action for N-BPs. Some of these very potent bisphosphonates, such as zoledronic acid, represent a third class of bisphosphonates that can act both via the inhibition of the mevalonate pathway and by the blockade of mitochondrial ADP/ATP translocase, which is known to be involved in the induction of apoptosis.

Adenine Nucleotide Translocator 1↗
PubMedDate not supplied

Enhanced lycopene productivity by manipulation of carbon flow to isopentenyl diphosphate in Escherichia coli.

Lycopene is a useful phytochemical that holds great commercial value. In our study the lycopene production pathway in E. coli originating from the precursor isopentenyl diphosphate (IPP) of the non-mevalonate pathway was reconstructed. This engineered strain of E. coli accumulated lycopene intracellularly under aerobic conditions. As a next step, the production of lycopene was enhanced through metabolic engineering methodologies. Various competing pathways at the pyruvate and acetyl-CoA nodes were inactivated to divert more carbon flux to IPP and subsequently to lycopene. It was found that the ackA-pta, nuo mutant produced a higher amount of lycopene compared to the parent strain. To further enhance lycopene production, a novel mevalonate pathway, in addition to the already existing non-mevalonate pathway, was engineered. This pathway utilizes acetyl-CoA as precursor, condensing it to form acetoacetyl-CoA and subsequently leading to formation of IPP. Upon the introduction of this new pathway, lycopene production increased by over 2-fold compared to the ackA-pta, nuo mutant strain.

Carbon↗
PubMedDate not supplied

Inhibition of farnesyl protein transferase by monoterpene, curcumin derivatives and gallotannin.

Ras proteins must be isoprenylated at a conserved cysteine residue near the carboxyl terminus (Cys-186 in mammalian Ras p21 proteins) in order to extend their biological activity. Previous studies have indicate an intermediate in the mevalonate pathway, most likely farnesyl pyrophosphate, is the donor of this isoprenyl group, and that using inhibitors of the mevalonate pathway could block the transforming properties of ras oncogene. Unfortunately, mevalonate is a precursor of various end products essential to mammalian cells, such as dolichols, ubiquinones, heme A, and cholesterol. In this study, we partially purified farnesyl protein transferase (FPTase) capable of catalyzing the farnesylation of unprocessed Ras p21 proteins in vitro from porcine kidney epithelial-like LLC-PK 1 cells, human lung adenocarcinoma A549 cells and human pancreatic cancer MIA PaCa-2 cells. This FPTase activity requires a divalent cation, such as Mg2+ or Zn2+ ions, sulfhydryl protecting agent, DTT, as well as certain pH which is linear with time and with enzyme concentration, and is present in many mammalian normal cell and tumor cell lines. Sequentially, we observed the effects of the monoterpene compound, d-limonene; curcumin derivatives, CD-I and CD-II; polyphenol compound, gallotannin; Salvia miltiorrhiza derivative, SMD; and retinoid acid derivative, RAD on FPTase activity. We found that curcumin derivatives and gallotannin had a strong inhibition on FPTase besides d-limonene, while gallotannin was the strongest among synthetic and natural compounds tested. Salivia miltiorrhiza and retinoid acid derivatives had no influence on FPTase activity. Our results suggest that compounds containing polyphenol hydroxyl may be a new source of FPTase inhibitors. The experiment also showed that availability of an in vitro farnesyl protein transferase assay could be useful in screening for potential inhibitors of ras oncogene function that will not interfere with other aspects of the mevalonate pathway.

Alkyl and Aryl Transferases↗