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PubMed1990

Glycosphingolipids in insects. Chemical structures of two variants of a glucuronic-acid-containing ceramide hexasaccharide from a pupae of Calliphora vicina (Insecta: Diptera), distinguished by a N-acetylglucosamine-bound phosphoethanolamine sidechain.

The two major components of the acidic glycolipid fraction from the pupae of Calliphora vicina were isolated using high-performance liquid chromatography. The acidic moiety was identified as glucuronic acid by beta-glucuronidase cleavage and gas chromatographic analysis as the pentafluoropropionyl derivative. The structures of the carbohydrate moiety were elucidated by peracetylation, methylation, exoglycosidase cleavage, fast-atom-bombardment mass spectrometric and 1H-nuclear magnetic resonance spectroscopic analysis. The only difference between the two hexasaccharide variants was the presence, in one of them, of a between the two hexasaccharide variants was the presence, in one of them, of a phosphoethanolamine (AeP) sidechain on the third sugar of the sequence, i.e. N-acetylglucosamine. The composition of the ceramide moiety was dominated by a C20:0 fatty acid (arachidic acid) and a C14:1 sphingoid base (tetradecasphing-4-enine). The chemical structures of the two insect acidic glycosphingolipids were determined to be: GlcA(beta 1-3)Gal-(beta 1-3)GalNAc(beta 1-4)GlcNAc(beta 1-3)Man (beta 1-4)Glc(beta 1-1)Cer; GlcA(beta 1-3)Gal(beta 1-3)GalNAc(beta 1-4)[2AeP-6]-GlcNAc(beta 1-3) Man(beta 1-4)Glc(beta 1-1)Cer. Such glucuronic-acid-containing insect glycosphingolipids have been given the generic name arthrosides, with the implied synonymity to the gangliosides.

Acetylglucosamine↗
PubMed1999

The glucuronic acid utilization gene cluster from Bacillus stearothermophilus T-6.

A lambda-EMBL3 genomic library of Bacillus stearothermophilus T-6 was screened for hemicellulolytic activities, and five independent clones exhibiting beta-xylosidase activity were isolated. The clones overlap each other and together represent a 23.5-kb chromosomal segment. The segment contains a cluster of xylan utilization genes, which are organized in at least three transcriptional units. These include the gene for the extracellular xylanase, xylanase T-6; part of an operon coding for an intracellular xylanase and a beta-xylosidase; and a putative 15.5-kb-long transcriptional unit, consisting of 12 genes involved in the utilization of alpha-D-glucuronic acid (GlcUA). The first four genes in the potential GlcUA operon (orf1, -2, -3, and -4) code for a putative sugar transport system with characteristic components of the binding-protein-dependent transport systems. The most likely natural substrate for this transport system is aldotetraouronic acid [2-O-alpha-(4-O-methyl-alpha-D-glucuronosyl)-xylotriose] (MeGlcUAXyl3). The following two genes code for an intracellular alpha-glucuronidase (aguA) and a beta-xylosidase (xynB). Five more genes (kdgK, kdgA, uxaC, uxuA, and uxuB) encode proteins that are homologous to enzymes involved in galacturonate and glucuronate catabolism. The gene cluster also includes a potential regulatory gene, uxuR, the product of which resembles repressors of the GntR family. The apparent transcriptional start point of the cluster was determined by primer extension analysis and is located 349 bp from the initial ATG codon. The potential operator site is a perfect 12-bp inverted repeat located downstream from the promoter between nucleotides +170 and +181. Gel retardation assays indicated that UxuR binds specifically to this sequence and that this binding is efficiently prevented in vitro by MeGlcUAXyl3, the most likely molecular inducer.

Base Sequence↗
PubMed1993

[Mechanisms of the stimulating effect of d-glucuronic acid on the processes of bone marrow granulomonocytopoiesis in cytostatic myelodepression].

The mechanisms of regulating influence of D-glucuronic acid on granulomonocytopoiesis++ have been studied by using the model of cyclophosphamide-induced myelodepression. Increase of colony-stimulating and interleukin-1 activities production by hemopoiesis inducing microenvironment cells, the stimulation of hemopoietic islets and the different granulomonocytopoiesis precursor cells forming have been shown to be the base of activating action of D-glucuronic acid on bone marrow granulomonocytopoiesis recovery.

Animals↗
PubMed2003

Multidrug resistance-associated proteins: Export pumps for conjugates with glutathione, glucuronate or sulfate.

Many endogenous or xenobiotic lipophilic substances are eliminated from the cells by the sequence of oxidation, conjugation to an anionic group (glutathione, glucuronate or sulfate) and transport across the plasma membrane into the extracellular space. The latter step is mediated by integral membrane glycoproteins belonging to the superfamily of ATP-Binding Cassette (ABC) transporters. A subfamily, referred as ABCC, includes the famous/infamous cystic fibrosis transmembrane regulator (CFTR), the sulfonylurea receptors (SUR 1 and 2), and the multidrug resistance-associated proteins (MRPs). The name of the MRPs refers to their potential role in clinical multidrug resistance, a phenomenon that hinders the effective chemotherapy of tumors. The MRPs that have been functionally characterized so far share the property of ATP-dependent export pumps for conjugates with glutathione (GSH), glucuronate or sulfate. MRP1 and MRP2 are also mediating the cotransport of unconjugated amphiphilic compounds together with free GSH. MRP3 preferentially transports glucuronides but not glutathione S-conjugates or free GSH. MRP1 and MRP2 also contribute to the control of the intracellular glutathione disulfide (GSSG) level. Although these proteins are low affinity GSSG transporters, they can play essential role in response to oxidative stress when the activity of GSSG reductase becomes rate limiting. The human MRP4, MRP5 and MRP6 have only partially been characterized. However, it has been revealed that MRP4 can function as an efflux pump for cyclic nucleotides and nucleoside analogues, used as anti-HIV drugs. MRP5 also transports GSH conjugates, nucleoside analogues, and possibly heavy metal complexes. Transport of glutathione S-conjugates mediated by MRP6, the mutation of which causes pseudoxantoma elasticum, has recently been shown. In summary, numerous members of the multidrug resistance-associated protein family serve as export pumps that prevent the accumulation of anionic conjugates and GSSG in the cytoplasm, and play, therefore, an essential role in detoxification and defense against oxidative stress.

ATP-Binding Cassette Transporters↗
PubMed1994

Characterization of glucuronic acid conjugates of a novel angiotensin receptor antagonist.

Nanogram quantities of glucuronic acid conjugates of GR117289 in rat and dog bile have been analysed by semi-microbore high-performance liquid chromatography (HPLC)/ionspray mass spectrometry with on-line UV diode array detection. The determination of drug metabolites in bile has often proved problematical due to the large number of endogenous components in this biological matrix, in particular the bile acids. Semi-microbore HPLC is useful for concentrating small quantities of material and, in combination with an on-line diode array detector, for distinguishing between drug related and endogenous components. A novel angiotensin II receptor antagonist, GR117289, had proved difficult to analyse by thermospray mass spectrometry because of its thermal lability. The use of the less thermally dependent technique of ionspray mass spectrometry allowed the characterization of nanogram quantities of glucuronic acid metabolites of GR117289 in bile.

Angiotensin Receptor Antagonists↗
PubMed1996

Two kinetically-distinct components of UDP-glucuronic acid transport in rat liver endoplasmic reticulum.

Previous studies have documented the presence of protein-mediated transport of UDP-glucuronic acid (UDP-GlcUA) in rat liver endoplasmic reticulum (ER). Measurement of uptake at varying concentrations of high specific activity [beta-32P]UDP-GlcUA has revealed the presence of a two component UDP-GlcUA transporting system. Transport at low substrate concentrations occurred predominantly via a high affinity component (K(m) = 1.6 microM), whereas a low affinity component (K(m) = 38 microM) predominated at high substrate concentrations. The K(m) for the high affinity system is in agreement with that previously published, while the low affinity component is a new finding. The uptake of UDP-GlcUA was temperature-sensitive, time dependent, and saturable for both components. The high affinity transport was affected by trans-stimulation and cis-inhibition by UDP-N-acetylglucosamine (UDP-GlcNAc); however, the same concentrations of UDP-GlcNAc had less effect on the low affinity system. In order to further study the two transport components, various inhibitors of anion transport carriers were tested. The high affinity component was strongly inhibited by 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS) and furosemide, while the low affinity system was less sensitive to these reagents. Dose-dependent inhibition by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) was found for both transport systems. Probenecid was found to be a weak inhibitor of both components of the UDP-GlcUA uptake. Finally, the major metabolite of 3'-azido-3'-deoxythymidine, 3'-azido-3'-deoxythymidine monophosphate (AZTMP), was able to inhibit the uptake of UDP-GlcUA by both components. The results indicate the presence of two carrier-mediated UDP-glucuronic acid transporting components in rat liver ER.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1983

A soybean lectin having 4-O-methyl-D-glucuronic acid specificity.

Evidence is presented for the presence of a new lectin activity in soybean seeds [Glycine max (L.) Merrill] that has specificity towards the 4-O-methyl-D-glucurono-L-rhamnan exopolysaccharide produced by certain strains of Rhizobium japonicum. Bacterial agglutination and precipitin reactions revealed the lectin activity in phosphate-buffered saline extracts of seeds of all cultivars tested, including the "lectinless" varieties. Reaction of such extracts with carbohydrate haptens demonstrated that the specificity of the binding was towards 4-O-methyl-D-glucuronic acid, D-glucuronic acid and their methyl glycosides.

Binding Sites, Antibody↗
PubMed1982

The formation of beta-glucuronidase resistant glucuronides by the intramolecular rearrangement of glucuronic acid conjugates at mild alkaline pH.

It is well known to carbohydrate chemists that substituted sugars may undergo facile rearrangement involving the migration of the aglycone from --OH to adjacent --OH. Despite the importance of glycoside conjugates, notably involving glucuronic acid, in the metabolism of xenobiotics, drug metabolism workers have neglected this phenomenon. The potential rearrangement of glucuronides from the biosynthetic C-1 isomers to other positional and stereo-isomers is important, since only 1-O-substituted beta-D-glucosiduronates are substrates for beta-glucuronidase, which is commonly used to identify such conjugates. The intramolecular rearrangement of clofibryl glucuronide has been studied over the pH range 5.2-8.6, by enzymic hydrolysis with beta-glucuronidase, and by HPLC. The amount of clofibric acid released from the conjugate by beta-glucuronidase falls with increasing pH of preincubation above pH 7.4, and this is accompanied by the appearance of three new peaks, each containing both clofibric and glucuronic acids, in the HPLC traces of the incubation mixtures. Similar experiments with three other glucuronides, those of p-nitrophenol, phenolphthalein and 7-hydroxycoumarin, did not show any conversion to beta-glucuronidase resistant forms. The phenomenon of intramolecular rearrangement of ester glucuronides must be considered whenever beta-glucuronidase is used in the analysis of conjugates of carboxylic acids.

Chromatography, High Pressure Liquid↗
PubMed1987

Enhanced binding of morphine and nalorphine to opioid delta receptor by glucuronate and sulfate conjugations at the 6-position.

Effect of the modification of morphine and nalorphine by glucuronate and sulfate conjugations at the 3- and 6-positions on the binding to opioid receptors was examined in a particulate fraction of rat brain. Competing potencies of both drugs against [3H]morphine and [3H]leucine enkephalin bindings were extremely decreased by either glucuronate or sulfate conjugation at the 3-position. On the other hand, the potencies of morphine and nalorphine against [3H]leucine enkephalin binding were considerably enhanced by the conjugations at the 6-position, whereas the potencies against [3H]morphine binding were decreased. These altered interactions of the conjugates at the 6-position with the two ligands were attributed to their enhanced binding to delta-receptor and reduced binding to mu-receptor by Hill plot and modified Scatchard analysis. Resulted comparable and simultaneous interactions with mu- and delta- receptors were assumed to be a cause of the enhanced mu-receptor-directed analgesia of morphine and elevated same receptor-directed antagonistic effect of nalorphine, which have been found previously in our laboratory.

Animals↗
PubMed2005

Towards the synthesis of aryl glucuronides as potential heparanase probes. An interesting outcome in the glycosidation of glucuronic acid with 4-hydroxycinnamic acid.

This work describes our preliminary efforts towards the development of aryl glucuronides as potential probes for heparanase. During the course of these initial investigations, attempted glycosidation of methyl 2,3,4-tri-O-acetyl-alpha-D-glucopyranosyluronate trichloroacetimidate with 4-hydroxycinnamic acid gave a complex mixture of four different components. These were identified as the 1-cinnamyl glucuronate ester 13, the cinnamyl linked disaccharide 14, the glucuronate trichloroacetamide 15, and the glucuronyl alpha-fluoride 16. This paper rationalises the formation of each of these products, and reports our efforts in trying to optimise the formation of the alpha-fluoride 16.

Coumaric Acids↗
PubMed1999

The reaction of hyaluronic acid and its monomers, glucuronic acid and N-acetylglucosamine, with reactive oxygen species.

Synovial fluid is a approximately 0.15% (w/v) aqueous solution of hyaluronic acid (HA), a polysaccharide consisting of alternating units of GlcA and GlcNAc. In synovial fluid of patients suffering from rheumatoid arthritis, HA is thought to be degraded either by radicals generated by Fenton chemistry (Fe2+/H2O2) or by NaOCl generated by myeloperoxidase. We investigated the course of model reactions of these two reactants in physiological buffer with HA, and with the corresponding monomers GlcA and GlcNAc. meso-Tartaric acid, arabinuronic acid, arabinaric acid and glucaric acid were identified by GC-MS as oxidation products of glucuronic acid. When GlcNAc was oxidised, erythronic acid, arabinonic acid, 2-acetamido-2-deoxy-gluconic acid, glyceric acid, erythrose and arabinose were formed. NaOCl oxidation of HA yielded meso-tartaric acid; in addition, arabinaric acid and glucaric acid were obtained by oxidation with Fe2+/H2O2. These results indicate that oxidative degradation of HA proceeds primarily at glucuronic acid residues. meso-Tartaric acid may be a useful biomarker of hyaluronate oxidation since it is produced by both NaOCl and Fenton chemistry.

Acetylglucosamine↗
PubMed1984

Rapid chromatographic purification of urinary steroid glucuronates for determination of aldosterone secretion rate.

Aldosterone secretion rate (ASR) is utilized as a rapid screening procedure to detect subtle forms of hypertension. A rapid and robust chromatographic method has been developed, based on easily prepared, rigid matrices, which permit the flow of urine by suction through sequential purification columns. Both major metabolites, aldosterone glucuronate and tetrahydroaldosterone glucuronate, are isolated in ca. 75% yield. They are hydrolyzed and quantitated by high-performance liquid chromatography-radioimmunoassay (HPLC-RIA) or, for bulk preparation, further purified by preparative chromatofocusing. These two polar conjugates are isolated in nearly pure form by HPLC on a C2 column with a two-step gradient. An ASR determination can be completed in one to two working days; preparative-scale work takes somewhat longer.

Aldosterone↗
PubMed2002

Interaction of glucuronic acid and iduronic acid-rich glycosaminoglycans and their modified forms with hydroxyapatite.

Proteoglycans and their spatial arms, glycosaminoglycans (GAGs), are known to interact with hydroxyapatite (HAP) and have been implicated as important modulators of mineralisation. In the present study isotherm data (0.02 M sodium acetate, pH 6.8) revealed that the iduronic-rich GAGs heparan sulphate, heparin and dermatan sulphate showed greater binding onto HAP with higher adsorption maxima compared with the glucuronic acid-rich GAGs chondroitin-4-sulphate, chondroitin-6-sulphate and hyaluronan. Chemically desulphated chondroitin showed no adsorption onto HAP. With the exception of hyaluronan, the GAGs studied showed no desorbability in sodium acetate buffer only, whereas in di-sodium orthophosphate, desorption occurred much more readily. The data indicates that GAG chemistry and conformation in solution greatly influence the interaction of these molecules with HAP. The conformational flexibility of iduronic acid residues may be an important determinant in the strong binding of iduronic acid-rich GAGs to HAP, increasing the possibility of the appended anionic groups matching calcium sites on the HAP surface, compared with more rigid glucuronic acid residues. This work provides important information concerning interfacial adsorption phenomena between the organic-inorganic phases of mineralised systems.

Adsorption↗
PubMed1989

Evaluation of a versatile reversed-phase high-performance liquid chromatographic system using cethexonium bromide as ion-pairing reagent for the analysis of glucuronic acid conjugates.

An ion-pair high-performance liquid chromatographic technique has been developed to reduce the elution times of both glucuronic acid conjugates and their free aglycones. The chromatographic system combines the use of a reversed-phase column (LiChrospher CH-18; 5 microns) and a mobile phase of methanol (70-80%)-0.01 M phosphate buffer (pH 6.0) containing 2.5 mM cethexonium bromide as counter-ion at a flow-rate of 1 ml min-1. The hydrophobicity of this quaternary ammonium ion-pairing reagent and the high content of the organic modifier in the mobile phase provide close and short elution times for a wide structural variety of compounds (i.e. alcohols, phenols, steroids, carboxylic acids) and their conjugates with glucuronic acid (capacity factors lower than 7.5), without compromising the selectivity with respect to endogenous compounds of the microsomal incubation medium and urine. Advantages of cethexonium bromide over conventional tetrabutylammonium salts are clearly demonstrated, and the described system was applied to the simultaneous quantitation of clofibric acid and its acylglucuronide in human urine and validated for a pharmacogenetics purpose.

Animals↗
PubMed2005

Density functional study of the conformational space of 4C1 D-glucuronic acid.

The conformational space of (4)C(1) alpha- and beta-d-glucuronic acid was scanned by HF/3-21G(p) calculations followed by optimization of the 15 most stable structures for each, using the B3LYP density functional theory method in conjunction with a diffuse polarized valence triple-zeta basis set. We found a general preference of the alpha anomers in the isolated molecules in agreement with the large endo-anomeric hyperconjugation effects in these structures. From the other intramolecular interactions (exo-anomeric hyperconjugation, hydrogen-bonding, dipole-dipole, and steric interactions), the effect of the hydrogen bonding is the most pronounced and plays a major role in determining the stability order within the alpha and beta series. The most stable conformer of both alpha and beta (4)C(1) d-glucuronic acid is the structure with the maximum number (5) of intramolecular hydrogen bonds. Introduction of solvent (water) effects by the SCI-PCM model resulted in two characteristic changes of the energetic properties: the gas-phase stability order changed considerably, and the energy range of the 15 most stable conformers decreased from 30 to 15 kJ/mol. The geometrical parameters reflect well the superimposed effects of hyperconjugation and hydrogen-bonding interactions. Most characteristics are the variations of the C-O bond distances (within a range of 0.04 A) upon the combined intramolecular effects.

Carbon↗
PubMed2006

The SPASIBA force field for chondroitin sulfate: vibrational analysis of D-glucuronic and N-acetyl-D-galactosamine 4-sulfate sodium salts.

Normal-mode analyses were carried out on the two components of the chondroitin 4-sulfate linear glycosaminoglycan, a copolymer implying alternate D-glucuronate beta-(1-->3) and N-acetyl-D-galactosamine 4-sulfate beta-(1-->4) (hereafter named D-galactosamine 4-sulfate) residues. Scaled quantum mechanical calculations (SQM) using the density functional theory approach at different levels of theory (B3LYP/6-31G** and B3LYP/6-31++G**) were performed to obtain correct vibrational assignments. The SPASIBA empirical force field parameters were then obtained from both theoretical predictions and observed IR and Raman data. It is shown that calculations including diffuse functions at the B3LP/6-31++G** level and the introduction of the Na+ counterion are necessary to give correct assignments of the CO2- symmetric (nu(s)) and antisymmetric (nu(a)) stretching modes for the glucuronic carboxylate residue.

Acetylgalactosamine↗
PubMed2002

Conversion of glucuronic acid glycosides to novel bicyclic beta-lactams.

[reaction: see text] Methodology for the conversion of glucuronic acid glycosides to novel bicyclic beta-lactams is reported. Using this strategy, we prepared two novel templates suitable for use in combinatorial chemistry strategies for the construction of a number of interesting beta-lactam motifs. Key features of this strategy include a diastereoselective Ferrier reaction of a glucuronic acid glucal, selective beta-lactam ring formation using a cyclic allylic alcohol, and a chemoselective benzylic oxidation.

Combinatorial Chemistry Techniques↗
PubMed1974

Stimulation of microsomal uridine diphosphate glucuronyltransferase by glucuronic acid derivatives.

The glucuronic acid adducts of 1-naphthol, 2-naphthol and 4-methylumbelliferone activate microsomal UDP-glucuronyltransferase (EC 2.4.1.17) when the enzyme is assayed with p-nitrophenol as aglycone. Phenyl glucuronide and oestriol 3beta-glucuronide also activate UDP-glucuronyltransferase. but to a lesser extent. Activation by glucuronides is not dependent on metal ions, but is blocked by prior treatment of microsomal fractions with p-chloromercuribenzoate. The kinetic mechanism of activation is concluded to be an increase in the affinity of the enzyme for UDP-glucuronic acid. Activation by 1-naphthyl glucuronide, at high concentrations of p-nitrophenol, is not affected by 1-naphthol. Apparently 1-naphthyl glucuronide activates the preparation by binding at a site that is separate from the site of glucuronidation of 1-naphthol. Further evidence for the existence of distinct effector sites for the glucuronides was provided by the finding that activation by glucuronides is inhibited competitively by aglycone glucosides. These glucosides do not inhibit the rate of glucuronidation of p-nitrophenol in the absence of glucuronide adducts, nor do they alter the rate of glucuronidation of 1-naphthol. When UDP-glucuronyltransferase is assayed with 1-naphthol as aglycone it is activated by p-nitrophenyl glucuronide, 4-methyl-umbelliferyl glucuronide and under appropriate conditions by its own glucuronide. These activations are similarly inhibited by aglycone glucosides. p-Nitrophenyl glucuronide also stimulates the rate of glucuronidation of o-aminophenol, o-aminobenzoate and bilirubin.

Animals↗