Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Polyisoprenyl Phosphates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1985

Dolichyl phosphate metabolism in brain. Developmental increase in polyisoprenyl phosphate phosphatase activity.

The enzymatic dephosphorylation of endogenous and exogenous dolichyl phosphate (Dol-P) by membrane preparations from calf brain has been reported previously (Burton, W.A., Scher, M.G., and Waechter, C. J. (1981) Arch. Biochem. Biophys. 208, 409-417). The study presented here shows that polyisoprenyl phosphate phosphatase activity increases with age in crude microsomal fractions from white (glial-enriched) and grey (neuronal-enriched) matter of pig brain. A kinetic analysis of grey matter phosphatase activity revealed that the apparent Km values for Dol-P are similar for membranes from adults (0.13 mM) and prenatal subjects (0.12 mM), but the Vmax is significantly higher in adults. In direct contrast to this result, the specific activity of dolichol kinase is nearly 2-fold higher in membranes from pig brain grey matter of prenatal subjects as compared to identical preparations from animals 90 days of age. While the changes in kinase and phosphatase activity are approximately 2-fold, reciprocal changes in these activities would enhance shifts in the metabolic balance of a phosphorylation-dephosphorylation process. In another aspect of this study on polyisoprenyl phosphate phosphatase in nervous tissue, membrane preparations from calf brain are shown to dephosphorylate S- and R-Dol-P. Similar apparent Km values were obtained for S-Dol-P and R-Dol-P, but the Vmax for the dephosphorylation reaction was found to be 1.8-fold greater for S-Dol-P. These results extend the description of polyisoprenyl phosphate phosphatase activity in brain and provide information on developmental changes in phosphatase and kinase activities involved in Dol-P metabolism in nervous tissue.

Age Factors↗
PubMed1986

Characterization of polyisoprenyl phosphate phosphatase activity in rat liver.

The polyisoprenyl phosphate dephosphorylating activity of rat liver has been investigated with regard to substrate specificity, subcellular distribution, and transmembrane orientation. Total liver microsomes were employed as a source of enzymatic activity against a variety of 32P-labeled substrates. Susceptibility to dephosphorylation followed the order solanesyl phosphate greater than alpha-cis-polyprenyl 19-phosphate = alpha-trans-polyprenyl 19-phosphate = dihydrosolanesyl phosphate greater than (S)-dolichyl 19-phosphate = (R)-dolichyl 19-phosphate = (R,S)-dolichyl 11-phosphate. There appeared to be no major effect of chain length from 11 to 20 isoprenes. Data obtained from inhibition studies using solanesyl [32P]phosphate as substrate were consistent with the substrate specificity studies and suggested that a single activity is responsible. With dolichyl [32P]phosphate as substrate, the phosphatase specific activity of the subcellular fractions prepared from rat liver was found to follow the sequence Golgi = smooth endoplasmic reticulum greater than plasma membrane greater than lysosomes = rough endoplasmic reticulum greater than nuclei greater than mitochondria. Transmembrane topography studies, using enzyme latency as a criterion, were consistent with an orientation of the active site facing the cytoplasm.

Animals↗
PubMed2000

Polyisoprenyl phosphate signaling: topography in human neutrophils.

To determine the relationship of polyisoprenyl phosphate (PIPP) remodeling and signaling to the activation state of human neutrophils (PMN), we examined the impact of leukotriene B(4) (LTB(4)) on the conversion of a unique bioactive isoprenoid (presqualene diphosphate: PSDP), recently identified as a novel endogenous signaling molecule. LTB(4) initiated rapid decrements in total PSDP that were concurrent with the respiratory burst (e.g., O(-2) formation). PSDP was identified in nuclear (39%)-, granule (36%)-, and plasma membrane (16%)-containing fractions of PMN. LTB(4) receptor (BLT) activation led to a decrease in nuclear PSDP and concomitant increase in granule-associated PSDP. In addition, PMN nuclei displayed PSDP associated with chromatin as established by mass spectrometry. Together, these results indicate that PSDP is present in membranes and receptor activation rapidly initiates subcellular PIPP remodeling (i.e., conversion) and distribution predominantly to granule membranes. Moreover, identification of nuclear PSDP provides the basis for novel roles for PIPP and PSDP in nuclear-associated signaling events.

Biological Transport↗
PubMed1997

Polyisoprenyl phosphate specificity of UDP-GlcNAc:undecaprenyl phosphate N-acetylglucosaminyl 1-P transferase from E.coli.

N-Acetyl-D-glucosaminylpyrophosphorylundecaprenol (GlcNAc-P-P-Und), an intermediate in the biosynthesis of the enterobacterial common antigen in E.coli and some O-antigen chains in gram-negative bacteria, is formed by the transfer of GlcNAc 1-P from UDP-GlcNAc to Und-P, analogous to the reaction forming GlcNAc-P-P-dolichol (GlcNAc-P-P-Dol) in mammalian cells. Since the microsomal enzyme from animal cells exhibits a strong preference for Dol-P, which contains a saturated alpha-isoprene unit, the polyisoprenyl phosphate specificity of the homologous bacterial enzyme was characterized. The enzyme remained bound to the membrane fraction when spheroplasts, formed by lysozyme-EDTA treatment, were lysed in hypotonic buffer. GlcNAc-P-P-Und synthase (GPT) activity was elevated in a strain of E.coli bearing the rfe gene, which encodes GPT on a multicopy plasmid, and virtually absent from rfe null mutants. GPT actively utilized fully unsaturated polyprenyl phosphate (Poly-P) substrates with maximal activity seen with (C55) Und-P, but was unable to utilize (C55)Dol-P. This substrate specificity contrasts with the microsomal GPT from pig brain, which actively utilized (C55)Dol-P, but not Und-P, as substrate. GPT activity bound to particulate fractions from three strains of bacilli also exhibited a strict preference for fully unsaturated Poly-P substrates. Unexpectedly, E.coli GPT activity cofractionated with the cytosolic marker enzyme, beta-galactosidase, and not the membrane-bound enzyme, D-lactate dehydrogenase, in cells disrupted in a French pressure cell. The properties and polyisoprenyl phosphate specificity of the soluble form of GPT were identical to the activity associated with the membrane preparations obtained from spheroplasts. The evolutionary and functional significance of the use of polyisoprenyl glycosyl carrier lipids with saturated alpha-isoprene units in eukaryotes remains uncertain.

Antigens, Bacterial↗
PubMed2006

Regulation of phosphatidylinositol 3-kinase by polyisoprenyl phosphates in neutrophil-mediated tissue injury.

Neutrophils play a central role in host defense, inflammation, and tissue injury. Recent findings indicate a novel role for polyisoprenyl phosphates (PIPPs) as natural down-regulatory signals in neutrophils. The relationship between PIPPs and neutrophil early activating signals, such as phosphoinositides, has not been previously determined. Here, we establish presqualene diphosphate (PSDP) as an endogenous PIPP regulator of phosphatidylinositol 3-kinase (PI3K). In human neutrophils, leukotriene B4 (LTB4) triggered rapid decreases in PSDP and reciprocal increases in PI3K activity. In addition, PSDP was identified by gas chromatography/mass spectrometry in p110gamma-PI3K immunoprecipitates obtained 30 s after LTB4, indicating a physical interaction between PSDP and PI3K in activated neutrophils. Moreover, PSDP (0.4-800 pmol) directly inhibited recombinant human p110gamma-PI3K activity. During an experimental model of lung injury and inflammation, a reciprocal relationship was also present in vivo for lung PSDP and PI3K activity. To investigate its therapeutic potential, we developed a new PSDP structural mimetic that blocked human neutrophil activation and mouse lung PI3K activity and inflammation. Together, our findings indicate that PSDP is an endogenous PI3K inhibitor, and suggest that in inflammatory diseases characterized by excessive neutrophil activation, PIPPs can serve as structural templates in a novel antineutrophil therapeutic strategy to limit tissue injury.

Animals↗
PubMed2005

Novel polyisoprenyl phosphates block phospholipase D and human neutrophil activation in vitro and murine peritoneal inflammation in vivo.

Leukocyte production of reactive oxygen species (ROS) is an essential component of the antimicrobial armament mounted during host defense, but when released to the extracellular milieu ROS can also injure host tissues and provoke inflammation. Polyisoprenyl phosphates (PIPPs) are constituents of human leukocyte membranes that regulate pivotal intracellular enzymes, such as phospholipase D (PLD). We prepared new PIPP mimetics and studied their impact in vivo on leukocyte activation, including ROS generation, in acute inflammation. In a stereospecific and concentration-dependent manner, the PIPP mimetics directly regulated Streptomyces chromofuscus phospholipase D (sPLD) action. The IC(50) for a (Z)-isomer of endogenous presqualene diphosphate (PSDP) was 100 nM. Structure-activity relationships were also determined for PIPP mimetic inhibition of recombinant human PLD1b, a prominent isoform in human leukocytes. The PIPP mimetic rank order for PLD1b inhibition differed from sPLD, although the (Z)-PSDP isomer remained the most potent PIPP mimetic for inhibition of both enzymes. Truncation of PLD1b to its catalytic core uncovered potential regulatory roles for both PSDP's isoprenoid and diphosphate moieties. The (Z)-PSDP isomer reduced ROS production by activated human leukocytes and decreased murine neutrophil accumulation (65.6%) and ROS production (38.5%) in vivo during zymosan A-initiated peritonitis. When administered intraperitoneally 2 h after zymosan A, the (Z)-PSDP isomer decreased in vivo neutrophil accumulation (72.5%) and ROS generation (74.4%) 6 h later in peritoneal exudates. Together, these results provide new means to protect and control unchecked inflammatory responses that characterize many human diseases.

Animals↗
PubMed1999

Polyisoprenyl phosphate (PIPP) signaling regulates phospholipase D activity: a 'stop' signaling switch for aspirin-triggered lipoxin A4.

It is of wide interest to understand how opposing extracellular signals (positive or negative) are translated into intracellular signaling events. Receptor-ligand interactions initiate the generation of bioactive lipids by human neutrophils (PMN), which serve as signals to orchestrate cellular responses important in host defense and inflammation. We recently identified a novel polyisoprenyl phosphate (PIPP) signaling pathway and found that one of its components, presqualene diphosphate (PSDP), is a potent negative intracellular signal in PMN that regulates superoxide anion generation by several stimuli, including phosphatidic acid. We determined intracellular PIPP signaling by autocoids with opposing actions on PMN: leukotriene B4 (LTB4), a potent chemoattractant, and lipoxin A4 (LXA4), a 'stop signal' for recruitment. LTB4 receptor activation initiated a rapid decrease in PSDP levels concurrent with activation of PLD and cellular responses. In sharp contrast, activation of the LXA4 receptor reversed LTB4-initiated PSDP remodeling, leading to an accumulation of PSDP and potent inhibition of both PLD and superoxide anion generation. Thus, an inverse relationship was established for PSDP levels and PLD activity with two PMN ligands that evoke opposing responses. In addition, PSDP directly inhibited both isolated human recombinant (Ki = 6 nM) and plant (Ki = 20 nM) PLD. Together, these findings link PIPP remodeling to intracellular regulation of PMN function and suggest a role for PIPPs as lipid repressors in signal transduction, a novel mechanism that may also explain aspirin's suppressive actions in vivo in cell signaling.

Aspirin↗
PubMed2002

Polyisoprenyl phosphates: natural antiinflammatory lipid signals.

Lipoxins (LX) and aspirin-triggered 15-epimer LX are leukocyte-derived eicosanoids generated during host defense that serve as down-regulatory signals. The specific intracellular events that govern cellular responses to inhibitory extracellular signals are of wide interest in order to understand pivotal intracellular events in diseases characterized by enhanced inflammatory responses, such as asthma, rheumatoid arthritis and atherosclerosis. We recently uncovered a novel role for polyisoprenyl phosphates, in particular presqualene diphosphate (PSDP), as natural down-regulatory signals in human neutrophils that directly inhibit phospholipase D and superoxide anion generation. Activation of LXA4 receptors (ALXR) reverses proinflammatory receptor-initiated decrements in PSDP and inhibits cellular responses. These findings represent evidence for a novel paradigm for lipid-protein interactions in the control of cellular responses, namely receptor-initiated degradation of repressor lipids that is subject to regulation by aspirin treatment via the actions of aspirin-triggered 15-epimer LX at the ALXR, and identify new templates for antiinflammatory drugs by design.

Anti-Inflammatory Agents↗
PubMed2000

A novel polyisoprenyl phosphate signaling cascade in human neutrophils.

Activation of neutrophil (PMN) surface receptors can evoke inflammation and tissue injury via aberrant release of excess effectors. The molecular mechanisms involved in host protection and control of PMN responses have yet to be defined. As Billah and coworkers (1989), and Exton (1997), for example, have pointed out, phospholipase D (PLD) signaling is known to play a pivotal role in PMN activation. Here, we determined the relationship between polyisoprenyl phosphate (PIPP) remodeling and PLD signaling and their impact in activation of PMN receptors by "pro-inflammatory" (leukotriene B4), and "anti-inflammatory" (aspirin-triggered lipoxinA4) ligands. Activation of the leukotriene B4 receptor initiated a rapid (within seconds) decrement in presqualene disphosphate (PSDP), activation of PLD and production of superoxide anions. This contrasts with activation of the LXA4 receptor by an aspirin-triggered lipoxin A4 mimetic that before leukotriene B4 gave an inverse relationship with rapidly increasing PSDP levels, and inhibition of both PLD activity and superoxide generation. PSDP proved to be a potent and direct-acting inhibitor of PLD (rhPLD1b:Ki = 5.9 nM), a property not shared by structurally related endogenous lipids. This PIPP also interacted with Src homology domains, selectively targeting SH2 and not SH3 domains. These results indicate a role for ligand-driven rapid PIPP remodeling as an early switch and "stop" signaling event that controls PMN. Moreover, they indicate that PSDP directly down-regulates PMN signaling events via select protein-target interactions controlling intracellular responses relevant in inflammation.

Animals↗
PubMed1998

Purification and characterization of a polyisoprenyl phosphate phosphatase from pig brain. Possible dual specificity.

Microsomal fractions from pig and calf brain catalyze the enzymatic dephosphorylation of endogenous and exogenous dolichyl monophosphate (Dol-P) (Sumbilla, C. A., and Waechter, C. J. (1985) Methods Enzymol. 111, 471-482). The Dol-P phosphatase (EC 3.1.3.51) has been solubilized by extracting pig brain microsomes with the nonionic detergent Nonidet P-40 and purified approximately 1,107-fold by a combination of anion exchange chromatography, polyethylene glycol fractionation, dye-ligand chromatography, and wheat germ agglutinin affinity chromatography. Treatment of the enzyme with neuraminidase prevented binding to wheat germ agglutinin-Sepharose, indicating the presence of one or more N-acetylneuraminyl residues per molecule of enzyme. When the highly purified polyisoprenyl phosphate phosphatase was analyzed by SDS-polyacrylamide gel electrophoresis, a major 33-kDa polypeptide was observed. Enzymatic dephosphorylation of Dol-P by the purified phosphatase was 1) optimal at pH 7; 2) potently inhibited by F-, orthovanadate, and Zn2+ > Co2+ > Mn2+ but unaffected by Mg2+; 3) exhibited an approximate Km for C95-Dol-P of 45 microM; and 4) was sensitive to N-ethylmaleimide, phenylglyoxal, and diethylpyrocarbonate. The pig brain phosphatase did not dephosphorylate glucose 6-phosphate, mannose 6-phosphate, 5'-AMP, or p-nitrophenylphosphate, but it dephosphorylated dioleoyl-phosphatidic acid at initial rates similar to those determined for Dol-P. Based on the virtually identical sensitivity of Dol-P and phosphatidic acid dephosphorylation by the highly purified enzyme to N-ethylmaleimide, F-, phenylglyoxal, and diethylpyrocarbonate, both substrates appear to be hydrolyzed by a single enzyme with an apparent dual specificity. This is the first report of the purification of a neutral Dol-P phosphatase from mammalian tissues. Although the enzyme is Mg2+-independent and capable of dephosphorylating Dol-P and PA, several enzymological properties distinguish this lipid phosphomonoesterase from PAP2.

Animals↗
PubMed1997

Polyisoprenyl phosphates in intracellular signalling.

In response to environmental stimuli, leukocyte membrane remodelling generates biologically active lipids that can serve as both intra- and extracellular mediators. There are several classes of lipids that can mediate inflammatory reactions. We report here on a new intracellular lipid signal that regulates oxygen-radical formation in neutrophils, a key response in microbial killing, inflammation and tissue injury. Screening of neutrophil-derived extracts rich in phosphorylated, non-saponifiable lipids revealed a potent inhibitor of superoxide anion (O2-) production. Structural analysis of biologically active fractions gave four major phosphorylated lipids: most abundant was presqualene diphosphate (PSDP). Upon activation of neutrophil receptors, PSDP and its monophosphate form, presqualene monophosphate (PSMP), undergo rapid remodelling. At submicromolar concentrations, PSDP but not PSMP inhibit O2- production by human neutrophil cell-free oxidase preparations. We prepared PSDP and PSMP by total organic synthesis and matched both the physical properties and biological activity of the neutrophil-derived compounds. Our results indicate that PSDP, a recognized intermediate of cholesterol biosynthesis, is present in immune effector cells and is a potent regulator of the cellular response in host defence.

Gas Chromatography-Mass Spectrometry↗
PubMed2006

Lipid mediators as agonists for the resolution of acute lung inflammation and injury.

Resolution of acute lung inflammation and injury is an active process; it is not merely the absence of proinflammatory signals. Restoration of homeostasis is coordinated by specific mediators and cellular events. In response to injury and inflammatory stimuli, infiltrating leukocytes and tissue-resident cells interact to generate lipoxins (LXs), which are bioactive eicosanoids derived from arachidonic acid. In contrast to proinflammatory leukotrienes and prostaglandins, LXs display potent antiinflammatory actions. LXA(4) interacts with a G protein-coupled receptor, termed ALX, that transduces counter-regulatory signals in part via intracellular polyisoprenyl phosphate remodeling. Presqualene diphosphate (PSDP) is a polyisoprenyl phosphate in human neutrophils that is rapidly converted to presqualene monophosphate (PSMP) upon cell activation. PSDP, but not PSMP, directly inhibits phospholipase D, phosphoinositol-3 kinase, and superoxide anion generation. LXs block PSDP turnover in neutrophil membranes to prevent proinflammatory responses. Hence, LX and polyisoprenyl phosphate signaling provide a counter-regulatory circuit to promote resolution of acute lung inflammation. LXA(4) and PSDP mimetics have been prepared with potent protective actions in murine models of asthma and acute lung injury.

Animals↗
PubMed1975

Glycoprotein biosynthesis: studies on thyroid mannosyltransferases. II. Characterization of a polyisoprenyl mannosyl phosphate and evaluation of its intermediary role in the glycosylation of exogenous acceptors.

The transfer of mannose from GDP-mannonse to exogenous glycopeptides and simple glycosides has been shown to be carried out by calf thyroid particles (Adamany, A. M., and Spiro, R. G. (1975) J. Biol. Chem. 250, 2830-2841). The present investigation indicates that this mannosylation process is accomplished through two sequential enzymatic reactions. The first involves the transfer of mannose from the sugar nucleotide to an endogenous acceptor to form a compound which has the properties of dolichyl mannosyl phosphate, while in the properties of dolichyl mannosyl phosphate, while in the second reaction this mannolipid serves as the glycosyl donor to exogenous acceptors. The particle-bound enzyme which catalyzed the first reaction utilized GDP-mannose (Km = 0.29 microM) as the most effective mannosyl donor, required a divalent cation, preferably manganese or calcium, and acted optimally at pH 6.3. Mannolipid synthesis was reversed by addition of GDP and a ready exchange of the mannose moiety was observed between [14C]mannolipid and unlabeled GDP-mannose. Exogenously supplied dolichyl phosphate, and to a lesser extent ficaprenyl phosphate, served as acceptors for the transfer reaction. The 14C-labeled endogenous lipid had the same chromatographic behavior as synthetic dolichyl mannosyl phosphate and enzymatically mannosylated dolichyl phosphate. The mannose component in the endogenous lipid was not susceptible to reduction with sodium borohydride and was released by mild acid hydrolysis. Alkaline treatment of the mannolipid released a phosphorylated mannose with properties consistent with that of mannose 2-phosphate. The formation of this compound which can arise from a cyclic 1,2-phosphate indicated, on the basis of steric considerations, that the mannose is present in beta linkage to the phosphate of the lipid. An intermediate role of the mannolipid in the glycosylation of exogenous acceptors was suggested by the observation that addition of dolichyl phosphate to thyroid particles resulted in a marked enhancement of mannose transfer from GDP-mannose to methyl-alpha-D-mannopyranoside acceptor while the presence of the glycoside caused a decrease in the mannolipid level. The glycosyl donor function of the polyisoprenyl mannosyl phosphate in the second reaction of the mannosylation sequence could be directly demonstrated by the transfer of [14C]mannose from purified endogenous mannolipid to either methyl-alpha-D-mannoside or dinitrophenyl unit A glycopeptides by thyroid enzyme in the presence of Triton X-100. The mannosylation of the glycoside was not inhibited by EDTA whereas the transfer of mannose to glycopeptide was cation-dependent. While dolichyl [14C]mannosyl phosphate, prepared from exogenous dolichyl phosphate, served as a donor of mannose to exogenous acceptor, this function could not be fulfilled by ficaprenyl [14C]mannosyl phosphate. The two-step reaction sequence carried out by thyroid enzymes which leads to the formation of an alpha-D-manno-pyranosyl-D-mannose linkage in exogenous acceptors by transfer of mannose from GDP-mannose through a beta-linked intermediate appears to involve a double inversion of anomeric configuration of this sugar.

Animals↗
PubMed1980

Partial characterization of the polyisoprenoid carrier of N-acetylglucosamine in Glycine max (soya bean).

Dolichyl phosphate (C55) and dolichyl phosphate prepared from liver were incubated with an enzyme prepared from soya-bean protoplasts. They both stimulated the transfer of radioactivity from UDP-D-glucose to lipid, but the stimulation was greater with liver dolichyl phosphate. Liver dolichyl phosphate with the soya-bean enzyme stimulated the transfer of radioactivity from UDP-N-acetyl-D-[U-14C]glucosamine to acidic lipid. UDP-D-[U-14C]glucose and UDP-N-acetyl-D-[U-14C]glucosamine were used with the soya-bean enzyme to prepare the glycosylated-acid-lipid acceptor of each sugar. Mild acid hydrolysis revealed that the radioactivity in the lipid glucosylated from UDP-glucose was present exclusively as glucose. That in the lipid glycosylated from UDP-N-acetylglucosamine was present mostly as N-acetylglucosamine. The soya-bean acidic-lipid acceptors of glucose and N-acetylglucosamine were stable to both catalytic hydrogenation and treatment with hot aqueous phenol; they behaved in a similar way as authentic alpha-saturated glucosylated polyisoprenyl phosphates. The soya-bean acidic-lipid acceptors of glucose and N-acetylglucosamine were eluted as deoxycholate complexes from a Sephadex column. In comparison with glucosylated polyisoprenyl phosphates of known size, the patterns of elution indicated that both soya-bean lipids contained a polyisoprenoid chain of 18 isoprene units.

Acetylglucosamine↗
PubMed2006

Identification and functional characterization of a presqualene diphosphate phosphatase.

Presqualene diphosphate (PSDP) is a bioactive lipid that rapidly remodels to presqualene monophosphate (PSMP) upon cell activation (Levy, B. D., Petasis, N. A., and Serhan, C. N. (1997) Nature 389, 985-990). Here, we have identified and characterized a phosphatase that converts PSDP to PSMP. Unlike the related polyisoprenyl phosphate farnesyl diphosphate (FDP), PSDP was not a substrate for type 2 lipid phosphate phosphohydrolases. PSDP phosphatase activity was identified in activated human neutrophil (PMN) extracts and partially purified in the presence of Nonidet P-40 with gel filtration and anion exchange chromatography. Peptide sequencing of a candidate phosphatase was consistent with phosphatidic acid phosphatase domain containing 2 (PPAPDC2), an uncharacterized protein that contains a lipid phosphate phosphohydrolase consensus motif. Recombinant PPAPDC2 displayed diphosphate phosphatase activity with a substrate preference for PSDP > FDP > phosphatidic acid. PPAPDC2 activity was independent of Mg(2+) and optimal at pH 7.0 to 8.0. Incubation of [(14)C]FDP with recombinant human squalene synthase led to [(14)C]PSDP and [(14)C]squalene formation, and in the presence of PPAPDC2, [(14)C]PSMP was generated from [(14)C]PSDP. PPAPDC2 mRNA was detected in human PMN, and is widely expressed in human tissues. Together, these findings indicate that PPAPDC2 in human PMN is the first lipid phosphate phosphohydrolase identified for PSDP. Regulation of this activity of the enzyme may have important roles for PMN activation in innate immunity.

Amino Acid Sequence↗
PubMed2005

Lipid sulfates and sulfonates are allosteric competitive inhibitors of the N-terminal phosphatase activity of the mammalian soluble epoxide hydrolase.

The EPXH2 gene encodes for the soluble epoxide hydrolase (sEH), a homodimeric enzyme with each monomer containing two domains with distinct activities. The C-terminal domain, containing the epoxide hydrolase activity (Cterm-EH), is involved in the metabolism of arachidonic acid epoxides, endogenous chemical mediators that play important roles in blood pressure regulation, cell growth, and inflammation. We recently demonstrated that the N-terminal domain contains a Mg2+-dependent lipid phosphate phosphatase activity (Nterm-phos). However, the biological role of this activity is unknown. The inability of known phosphatase inhibitors to inhibit the Nterm-phos constitutes a significant barrier to the elucidation of its function. We describe herein sulfate, sulfonate, and phosphonate lipids as novel potent inhibitors of Nterm-phos. These compounds are allosteric competitive inhibitors with K(I) in the hundred nanomolar range. These inhibitors may provide a valuable tool to investigate the biological role of the Nterm-phos. We found that polyisoprenyl phosphates are substrates of Nterm-phos, suggesting a possible role in sterol synthesis or inflammation. Furthermore, some of these compounds inhibit the C-terminal sEH activity through a noncompetitive inhibition mechanism involving a new binding site on the C-terminal domain. This novel site may play a role in the natural in vivo regulation of epoxide hydrolysis by sEH.

Allosteric Regulation↗
PubMed2000

Lipoxins, aspirin-triggered 15-epi-lipoxin stable analogs and their receptors in anti-inflammation: a window for therapeutic opportunity.

LXs and 15-epimer LXs are generated during cell-cell interactions that occur during multicellular host response to inflammation, tissue injury or host defense. Results indicate that they are present in vivo during human illness and carry predominantly counter-regulatory biological actions opposing the action of well-characterized mediators of inflammation that appear to lead to resolution of the inflammatory response or promotion of repair and wound healing. The first selective receptor of LXA4 was identified by direct ligand binding and was cloned and characterized. Its signaling involves a novel polyisoprenyl-phosphate pathway that directly regulates PLD (Levy et al. 1999a). LX- and 15-epimer-LX-stable analogs that resist metabolic inactivation were designed, synthesized and shown to be potent LX mimetics and novel topically active anti-inflammatory agents in animal models. These new investigational tools enable structure-function studies of LX signal transduction, further elucidation of the role of LX and 15-epimer LX in host responses and exploitation of their potent bioactions in the design of novel pharmacologic agents.

Animals↗