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PubMed1978

Isolation of a novel sphingoglycolipid containing glucuronic acid and 2-hydroxy fatty acid from Flavobacterium devorans ATCC 10829.

A new acidic sphingoglycolipid has been isolated from a Gram-negative, glucose-non-fermentative (obligatory aerobic) bacterium, Flavobacterium devorans ATCC 10829, by thin-layer chromatography on silica gel after mild alkaline hydrolysis of the cellular lipids. Chemical degradation studies, thin-layer chromatographic behavior, IR and mass-spectrometric analysis of the original and reduced glycolipid with LiA1H4 revealed that the lipid contained glucuronic acid, long-chain bases, and fatty acids in a molar ratio of approximately 1:1:1. The major long-chain bases were identified by gas chromatography-mass spectrometry as dihydrosphingosine (d-18 :0) and longer homologues, while the N-acyl group was exclusively 2-hydroxy myristic acid. The most probable structure of this glycolipid appeared to be a ceramide glucuronic acid (N-acyl dihydrosphingosine 1-glucuronic acid).

Flavobacterium↗
PubMed1980

Structural studies on cutinase, a glycoprotein containing novel amino acids and glucuronic acid amide at the N terminus.

Cutinase I and cutinase II, two extracellular enzymes produced by Fusarium solani pisi, were shown to be glycoproteins containing 4.3% and 5.1% carbohydrates, respectively. Upon treatment with alkali both enzymes generated chromophores which absorbed at 241 nm. Treatment of both proteins with alkaline NaB3H4 gave labeled protein and labeled monosaccharides. Hydrolysis of the labeled protein followed by chromatographic and enzymatic analyses of the products showed that alanine, 2-aminobutyrate, phenylalanine, tyrosine and L-gulonic acid accounted for nearly all of the 3H contained in the protein. The four labeled amino acids were shown to be 1:1 mixture of D and L isomers and 3H was nearly equally distributed between alpha and beta positions in each amino acid. The N-terminal amino group of cutinase I did not react with either phenylisothiocyanate of dansyl chloride. This amino group was suggested to be in amide linkage with glucuronic acid because upon treatment of the protein with neutral NaB3H4, gulonic acid attached to the protein became labeled and only gulonic acid was labeled when the protein was deglycosylated with HF prior to alkaline NaB3H4 treatment. Furthermore, N-gulonyglycine was isolated from the pronase digest of the labeled protein. Chromatographic identification and quantification of the labeled carbohydrates released from cutinase I by alkaline NaB3H4 showed that one mole of cutinase I has one mole each of mannose, arabinose, N-acetylglucosamine, and glucuronic acid O-glycosidically linked to serine, threonine, beta-hydroxyphenylalanine, and beta-hydroxytyrosine. In addition, the N-terminal glycine is in amide linkage with glucuronic acid. Since almost identical experimental results were obtained with cutinase II this protein is also suggested to have the same structural features as those suggested above for cutinase I.

Amino Acids↗
PubMed1970

Control of uridine diphosphate-glucose dehydrogenase synthesis and uridine diphosphate-glucuronic acid accumulation by a regulator gene mutation in Escherichia coli K-12.

Uridine diphosphate (UDP)-glucose dehydrogenase, the enzyme that converts UDP-glucose to UDP-glucuronic acid, was derepressed in a mucoid (capR9) strain of Escherichia coli K-12 and repressed in a nonmucoid (capR(+)) strain. A nonmucoid mutant (strain MC 152; capR9 non-2) derived from the mucoid strain accumulated large quantities of nucleotides. Among these nucleotides, UDP-glucuronic acid was identified as well as guanosine triphosphate and an adenosine diphosphate-sugar. UDP-glucose dehydrogenase was still derepressed in strain MC 152. When the nonmucoid mutant was transduced to the wild-type state for this regulator gene (capR(+)), the transductant was found to accumulate less total nucleotides, and the accumulation of UDP-glucuronic acid was abolished. UDP-glucose dehydrogenase was repressed in the capR(+)non-2 strain but not to the same extent that it was in the capR(+) strain.

Alcohol Oxidoreductases↗
PubMed1978

Urinary excretion of D-glucaric acid, total glucuronic acid and total porphyrins in porphyria cutanea tarda.

The urinary levels of D-glucaric acid, which is an index of hepatic microsome induction, and the excretion of glucuronic acid and porphyrins were measured in nine patients with Porphyria Cutanea Tarda (PCT) and twelve normal controls. The excretion of D-glucaric acid and glucuronic acid were respectively 3.5 and two times higher in PCT patients compared to controls. A statistical correlation could be demonstrated between urinary excretion of total porphyrins with that of glucaric and glucuronic acids. These findings indicate that microsomal function and porphyrin metabolic derangement are strictly related in PCT.

Fatty Liver↗
PubMed1977

Separation and allosteric properties of two forms of UDP-glucuronate carboxy-lyase.

DEAE-cellulose chromatography of partially purified preparations of UDP-glucuronate carboxy-lyase from wheat germ results in the separation of two forms of the enzyme. Both are fully active in the absence of added DPN, have indistinguishable molecular weights (210,000), but differ in charge and kinetic properties. Both are cooperatively activated by UDP-glucuronate, however Enzyme 1 is activated at lower concentrations than Enzyme 2. At low substrate concentrations (less than or equal to 5 micron), both enzymes are activated by UDP-glucose, 2 mM concentrations of activator increasing the activity of Enzyme 1 2-fold and of Enzyme 2 2.5-fold. UDP-xylose allosterically inhibits both enzymes. At substrate concentrations equal to the apparent Km values, inhibition of Enzyme 1 is much greater than that of Enzyme 2 (83 and 28% at 0.33 mM inhibitor concentration). The data suggest that synthesis of UDP-xylose is controlled both by substrate activation and product inhibition of UDP-glucuronate carboxy-lyase. The existence of a "more active" and a "less active" species of the enzyme suggests the possibility of two interconvertible forms of the same protein and the involvement of such interconversion in further regulation of UDP-xylose biosynthesis. However it is equally possible that both represent true isoenzymes.

Allosteric Regulation↗
PubMed2004

Identification and characterization of a UDP-D-glucuronate 4-epimerase in Arabidopsis.

One of the major sugars present in the plant cell wall is d-galacturonate, the dominant monosaccharide in pectic polysaccharides. Previous work indicated that one of the activated precursors necessary for the synthesis of pectins is UDP-d-galacturonate, which is synthesized from UDP-d-glucuronate by a UDP-d-glucuronate 4-epimerase (GAE). Here, we report the identification, cloning and characterization of a GAE6 from Arabidopsis thaliana. Functional analysis revealed that this enzyme converts UDP-d-glucuronate to UDP-d-galacturonate in vitro. An expression analysis of this epimerase and its five homologs in the Arabidopsis genome by quantitative RT-PCR and promoter::GUS fusions indicated differential expression of the family members in plant tissues and expression of all isoforms in the developing pollen of A. thaliana.

Arabidopsis↗
PubMed2002

Characterisation and immunolocation of an 87 kDa polypeptide associated with UDP-glucuronic acid decarboxylase activity from differentiating tobacco cells (Nicotiana tabacum L.).

UDP-glucuronic acid decarboxylase catalyses the reaction responsible for the formation of UDP-xylose and commits assimilate for the biosynthesis of cell wall polysaccharides and glycosylation of proteins. Xylose-rich polymers such as xylans are a feature of dicot secondary walls. Thus a cell culture system of tobacco transformed with the ipt gene from Agrobacterium tumefaciens for cytokinin production and which when manipulated with auxin and sucrose leads to induction of xylogenesis, has been used as a source for purification of the enzyme. UDP-glucuronic acid decarboxylase was purified by ion-exchange, gel filtration and affinity chromatography on Reactive Brown-Agarose. The native enzyme had an apparent M(r) of 220,000 which yielded a single subunit of 87,000 when analysed on SDS-PAGE using silver staining. This appears to be a novel form of the enzyme since a gene family encoding polypeptides around M(r) 40,000 with homology to the fungal enzyme also exists in plants. Using an antibody raised to the native 87 kDa form of the enzyme, this decarboxylase was localised mainly to to cambium and differentiating vascular tissue in tobacco stem, consistent with a role in the provision of UDP-xylose for the synthesis of secondary wall xylan. Further analysis using immunogold electron microscopy localised the 87 kDa UDP-glucuronic acid decarboxylase to the cytosol of developing vascular tissue.

Antibodies↗
PubMed2006

Biosynthesis of dermatan sulfate: chondroitin-glucuronate C5-epimerase is identical to SART2.

We identified the gene encoding chondroitin-glucuronate C5-epimerase (EC 5.1.3.19) that converts D-glucuronic acid to L-iduronic acid residues in dermatan sulfate biosynthesis. The enzyme was solubilized from bovine spleen, and an approximately 43,000-fold purified preparation containing a major 89-kDa candidate component was subjected to mass spectrometry analysis of tryptic peptides. SART2 (squamous cell carcinoma antigen recognized by T cell 2), a protein with unknown function highly expressed in cancer cells and tissues, was identified by 18 peptides covering 26% of the sequence. Transient expression of cDNA resulted in a 22-fold increase in epimerase activity in 293HEK cell lysate. Moreover, overexpressing cells produced dermatan sulfate chains with 20% of iduronic acid-containing disaccharide units, as compared with 5% for mock-transfected cells. The iduronic acid residues were preferentially clustered in blocks, as in naturally occurring dermatan sulfate. Given the discovered identity, we propose to rename SART2 (Nakao, M., Shichijo, S., Imaizumi, T., Inoue, Y., Matsunaga, K., Yamada, A., Kikuchi, M., Tsuda, N., Ohta, K., Takamori, S., Yamana, H., Fujita, H., and Itoh, K. (2000) J. Immunol. 164, 2565-2574) with a functional designation, chondroitin-glucuronate C5-epimerase (or DS epimerase). DS epimerase activity is ubiquitously present in normal tissues, although with marked quantitative differences. It is highly homologous to part of the NCAG1 protein, encoded by the C18orf4 gene, genetically linked to bipolar disorder. NCAG1 also contains a putative chondroitin sulfate sulfotransferase domain and thus may be involved in dermatan sulfate biosynthesis. The functional relation between dermatan sulfate and cancer is unknown but may involve known iduronic acid-dependent interactions with growth factors, selectins, cytokines, or coagulation inhibitors.

Amino Acid Sequence↗
PubMed1987

Characterization of sulfated glucuronic acid containing glycolipids reacting with IgM M-proteins in patients with neuropathy.

In some patients with neuropathy and plasma cell dyscrasia, the serum IgM M-proteins are known to bind to the myelin associated glycoprotein and to peripheral nerve glycolipids. We have isolated two acidic glycolipids which bind to the M-protein from human cauda equina by DEAE-Sephadex, Iatrobeads, and high performance liquid column chromatographies. The major acidic glycolipid migrated between GM1 and GD1a and the minor acidic glycolipid migrated between GD1a and GD1b. Their structures were elucidated by sugar analysis, enzymatic digestion, mild acid hydrolysis, permethylation, fast atom bombardment mass spectrometry, and NMR studies. Their core structure was confirmed to be paragloboside by high performance thin-layer chromatography-immunostaining using anti-paragloboside monoclonal antibody. Both acidic glycolipids lacked sialic acid but contained sulfated glucuronic acid as their acidic moiety. The sulfate group in the glucuronic acid was established by periodate oxidation and permethylation studies to be attached to the 3 position. The structures of the two acidic glycolipids are therefore consistent with the following: IV3GlcUA(3-sulfate)nLcOse4Cer and VI3GlcUA(3-sulfate)nLcOse6Cer. Additionally, the free carboxyl group on the glucuronic acid residue was shown to be necessary to bind the IgM M-proteins from neuropathy patients.

Antibodies, Monoclonal↗
PubMed1986

A general assay for UDPglucuronosyltransferase activity using polar amino-cyano stationary phase HPLC and UDP[U-14C]glucuronic acid.

The assay of UDPglucuronosyltransferase activity toward various substrates using UDP[U-14C]glucuronic acid is described. HPLC on a polar amino-cyano bonded phase column was used to separate radioactive glucuronides from unmetabolized UDP[U-14C]glucuronic acid and other labeled reaction products. Radioactivity was measured using flow-through scintillation counting. All the glucuronides analyzed, with one exception, chromatographed with the same retention time (9.0-9.6 min) under the conditions described. Glucuronide conjugates were identified by comparison with retention times of commercial glucuronide standards, using radioactive aglycones, or hydrolysis with beta-glucuronidase. The method provides a unified, sensitive (100-200 pmol of glucuronide product) and reproducible assay for a wide variety of UDPglucuronosyltransferase substrates, and could be extended to include many others.

Animals↗
PubMed1990

Purification and characterization of iduronic acid-rich and glucuronic acid-rich proteoglycans implicated in human post-burn keloid scar.

Small proteoglycans (PGs), extracted from human keloid scar tissue with 4M guanidinium chloride and fractionated by DEAE-cellulose chromatography, were separated by ethanol precipitation into one L-iduronic acid-rich and one D-glucuronic acid-rich fraction. The size of the L-iduronic acid-rich PG was 102 kDa with a 27 kDa glycosaminoglycan chain, that of the D-glucuronic acid-rich PG was 90 kDa with a 26 kDa glycosaminoglycan chain, and the protein core of both PGs was 14.5 kDa. The two PGs carried sulfate groups mostly attached at C-4 of the 2-amino-2-deoxy-D-galactose units. The N-terminal amino acid sequence of both was similar to human bone PGII (decorin), normal and hypertrophic scar, and human dermal tissue PG.

Amino Acid Sequence↗
PubMed1976

Modifications of drug metabolism by disulfiram and diethyldithiocarbamate. II. D-Glucuronic acid pathway.

Hepatic enzymes connected with the formation and metabolism of free D-glucuronic acid were affected in rats after treatment with disulfiram or diethyldithiocarbamate (300 mg/kg, intragastrically, per day, 4 X). The activities of UDPglucose dehydrogenase, UDPglucuronic acid pyrophosphatase, UDPglucuronosyltransferase and L-gulonate dehydrogenase were enhanced, while those of glucose-6-phosphate dehydrogenase, beta-glucuronidase and D-glucuronolactone dehydrogenase were inhibited. These changes were more pronounced with disulfiram than diethyldithiocarbamate. Treatment with phenobarbital (80 mg/kg, i.p., per day, 4 X) enhanced UDP glucuronosyl-transferase, but brought about different effects on the other enzymes. Concurrent administration of phenobarbital with disulfiram or diethyldithiocarbamate led to potentiation or antagonism of the primary effects of each compound when given alone. The results suggest that activation of the D-glucuronic acid pathway may proceed in various ways, and that it is not necessarily followed by a simultaneous induction of the microsomal mixed-function oxygenase activity.

Alcohol Oxidoreductases↗
PubMed1995

Conformational analysis of segments of oxidized cellulose. Part I: Molecular modelling of glucuronic acid dimers considering the effect of counter-ions and a polar environment.

Conformational analysis of various forms of glucuronic acid dimers as the model structures of oxidized cellulose has been performed using molecular mechanics with a CVFF force field. The effects of ionization of carboxyl groups, ion pairing with explicit consideration of counter-ions (Na+, Mg2+) and the implicit inclusion of a solvent effect via the dielectric constant, epsilon, have been simulated. The non-ionized glucuronic acid dimer shows conformational behaviour similar to that of unoxidized cellobiose. The ionization of COOH groups leads to strong destabilization of C and D conformers (with both COO- groups on the same side of the molecule), while complexation with counter-ions leads to strong stabilization of these forms which yield highly wound low-pitch helices. An increase in the solvent polarity has an attenuating effect on the behaviour described above.

Anions↗
PubMed1988

Glycogenolysis--and not gluconeogenesis--is the source of UDP-glucuronic acid for glucuronidation.

Differences in cofactor (NADPH and UDP-glucuronic acid) supply for various processes of biotransformation were studied by investigating the interrelations between glucose production (gluconeogenesis and glycogenolysis) and drug (p-nitrophenol, aminopyrine, phenolphthalein) biotransformation (hydroxylation and conjugation) in isolated murine hepatocytes. In glycogen-depleted hepatocytes prepared from animals fasted for 48 h (i) p-nitrophenol conjugation was decreased by 80% compared to the fed control, while aminopyrine oxidation was unaltered, (ii) addition of glucose or gluconeogenic substrates failed to increase the rate of p-nitrophenol conjugation, while the rate of p-nitrophenol and also aminopyrine oxidation was increased and (iii) gluconeogenesis was inhibited by 80% by aminopyrine oxidation: it was moderately decreased by p-nitrophenol oxidation and conjugation and remained unchanged by phenolphthalein conjugation. In hepatocytes prepared from fed mice (i) p-nitrophenol conjugation was independent of the extracellular glucose concentration, (ii) it was linked to the consumption of glycogen--addition of fructose inhibited p-nitrophenol glucuronidation only, while sulfation was unaltered and (iii) p-nitrophenol oxidation was not detectable: aminopyrine oxidation was not affected by fructose addition. It is suggested that UDP-glucuronic acid for glucuronidation derives predominantly from glycogen, while the NADPH generation for mixed function oxidation is linked to glucose uptake and/or gluconeogenesis in the liver.

Aminopyrine↗
PubMed1992

Glucuronic acid-containing glycosaminoglycans occur in otoconia: cytochemical evidence by hyaluronidase-gold labeling.

Localization of glucuronic acid-containing glycosaminoglycans in the gerbil utricle was examined, using a hyaluronidase-gold labeling technique with special emphasis on the otoconia. Otoconia and the gelatinous layer of the otoconial membrane were strongly labeled by hyaluronidase-gold. The secretory granules in supporting cells were also strongly labeled, suggesting that the organic matrix of otoconia is secreted from the supporting cells. Otoconia seem to lose labeling while they degenerated. The degenerating otoconia were observed to be absorbed into dark cells. Glucuronic acid-containing glycosaminoglycans occur in otoconia. These glycosaminoglycans may play a crucial role in the formation and degeneration of otoconia.

Animals↗
PubMed1987

Determination of the distribution of D-glucuronic acid units within the chain of pig-skin dermatan sulfate near the linkage region.

A method for analyzing the distribution of D-glucuronic acid units within the chain and near the linkage region of dermatan sulfate has been developed. The method consists of a chemical modification of the reducing terminal residue in the polysaccharide by reductive amination with excess 1,2-diaminoethane in the presence of sodium cyanoborohydride, desulfative fragmentation of the polysaccharide, labeled with 2-aminoethylamino (AEA) groups, in hot dimethyl sulfoxide containing 10% of water followed by 2,4-dinitrophenylation of the 2-aminoethylamino group, separation of the 2-(2,4-dinitrophenylamino)ethylamino labeled dermatan fragments from nonlabeled fragments on Octyl-Sepharose CL-4B gel, and determination of the uronic acid composition of the labeled fragments having various chain-length. A preparation of pig-skin dermatan sulfate (Mr 21,000, ratio of GlcA to total uronic acid, 93:500) showed an average distribution pattern of D-glucuronic acid residues near the linkage region of one N-acetylchondrosine unit in the disaccharide sequence 1-5(6) linked to the Xyl----Gal----Gal----GlcA residue, a cluster of 6-8 N-acetyldermosine units in the sequence 6(7)-12(13), and four separate N-acetylchondrosine units between the sequence adjacent to the N-acetyldermosine cluster and the sequence 23 or higher.

Animals↗
PubMed1981

Biosynthesis of dermatan sulphate. Loss of C-5 hydrogen during conversion of D-glucuronate to L-iduronate.

The formation of L-iduronic acid during biosynthesis of dermatan sulphate has been studied in culture human fibroblasts and in microsomes from the same cells. The cells were incubated with D-[14C]glucose and D-[5-3H]glucose for 72 h. The [14C,3H]dermatan sulphate was hydrolysed and the disaccharides obtained were acetylated and separated by ion-exchange chromatography. The ratio of 3H/14C was 0.36 for N-acetyldermosine and 1.36 N-acetylchondrosine. A microsomal preparation from the fibroblasts was incubated with UDP-D-[5-3H]glucuronic acid, UDP-D-[14C]glucuronic acid, UDP-N-acetyl-D-galactosamine and 3'-phospho-5'-adenylyl sulphate. The polymeric products were separated into nonsulphated and sulphated components which had 3H/14C ratios of 0.51 and 0.20 and contained 9% and 70% of their uronosyl residues in the L-ido-configuration, respectively. Chondroitinase-AC digestion of these polymers liberated all of the remaining 3H activity. Hydrolysis and N-acetylation followed by paper chromatography showed that the L-iduronic acid-containing products were devoid of 3H. The data obtained indicate that the epimerization of D-glucuronosyl to L-iduronosyl residues during biosynthesis of dermatan sulphate involves an abstraction of the C-5 hydrogen of the uronosyl residue.

Carbon Radioisotopes↗
PubMed1990

The poly-alpha- and -beta-1,4-glucuronic acid moiety of teichuronopeptide from the cell wall of the alkalophilic Bacillus strain C-125.

Teichuronopeptide is a structural component of the cell wall of alkalophilic Bacillus strain C-125 and is a complex composed of polyglutamate and polyglucuronate. A structural analysis of the polyglucuronic acid moiety was carried out. Periodate oxidation and Smith degradation of the moiety, and enzymic analysis after reduction of glucuronic acid to glucose, revealed that glucuronic acid bound together with alternately alpha- and beta-1,4-linkages.

Bacillus↗