A rapid method for seperation and identification of several hexuronic acids and hexuronic acid-containing oligosaccharides.
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Electrophoresis, Paper↗
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2-O-methyl-D-glucuronic acid, a new hexuronic acid of biological origin.
Acid hydrolysis of the extracellular polysaccharide of Porphyridium cruentum (a unicellular red alga) produced a mixture of aldobiuronic acids and free hexuronic acids. Fractionation of this mixture on an ion-exchange column yielded a hexuronic acid characterized as the title compound. Its identity was confirmed by chromatographic comparisons with the authentic compound, by reduction to the corresponding methylated aldose, by resistance to controlled lead tetra-acetate oxidation and by chemical-ionization mass spectrometry. Complete spectra have been deposited as Supplementary Publication SUP50062 (7 pages) with the British Library (Lending Division), Boston Spa, Wetherby, W. Yorkshire LS23 7BQ, U.K., from whom copies may be obtained under the terms given in Biochem. J. (1976) 153, 5.
Carbohydrates↗
Total synthesis of hexuronic acids.
Six stereoisomeric hexuronic acids (tert-butyl esters of methyl pyranosides) having the altro, manno, gluco, gulo, galacto, and talo configurations were obtained from cis,trans-tert-butyl 2-methoxy-5,6-dihydro-2H-pyran-6-carboxylate (5). The synthesis involved the following successive steps: epoxidation of the double bond in 5, opening of the epoxides with dimethylamine, Cope degradation of the dimethyl-amino derivatives, and hydroxylation of the double bond in the tert-butyl hex-3-enuronates. All compounds were obtained as pure diastereoisomers in racemic form.
Hexuronic Acids↗
Bilirubin conjugates of human bile. The excretion of bilirubin as the acyl glycosides of aldobiouronic acid, pseudoaldobiouronic acid and hexuronosylhexuronic acid, with a branched-chain hexuronic acid as one of the components of the hexuronosylhexuronide.
Structure elucidations have been performed on the bilirubin conjugates isolated from human hepatic bile as the phenylazo derivatives. The major bilirubin conjugates are excreted, not as was formerly thought in the form of glucuronides, but as the acyl glycosides of aldobiouronic acid, pseudoaldobiouronic acid and hexuronosylhexuronic acid. The isolated aldobiouronides are proposed to have the structures of an acyl 6-O-hexopyranosyluronic acid-hexopyranoside, an acyl 4-O-hexofuranosyluronic acid-d-glucopyranoside, and an acyl 4-O-beta-d-glucofuranosyluronic acid-d-glucopyranoside respectively, with the acyl radicals being those of the phenylazo derivative of bilirubin. The pseudoaldobiouronide is suggested to be the acyl 4-O-alpha-d-glucofuranosyl-beta-d -glucopyranosiduronic acid, with the acyl radical being that of the phenylazo derivative of vinylneoxanthobilirubinic acid. The hexuronosylhexuronide presumably is the acyl 4-O-(3-C-hydroxymethylribofuranosyluronic acid)-beta-d-glucopyranosiduronic acid, with the acyl radical being that of the phenylazo derivative of bilirubin. The 3-C-hydroxymethylriburonic acid, isolated as one of the components of the hexuronosylhexuronide, is the first natural branched-chain hexuronic acid to be detected, and the first branched-chain sugar ever detected in humans.
Azo Compounds↗
G.L.C. of the O-trimethylsilyl derivatives of hexuronic acids.
The free acids, sodium salts, and lactones of several hexuronic acids have been studied as their O-trimethylsilyl derivatives by gas-liquid chromatography using SE-30 and XE-60 liquid phases. Silylation was best performed in methyl sulphoxide. The equilibrium between the various forms of a hexuronic acid in methyl sulphoxide was also studied by g.l.c. following silylation. The hexamethyldisilazane used in the silylation disturbed the equilibrium attained in the solvent, but this was overcome by premixing the hexamethyldisilazane with chlorotrimethylsilane. Methyl sulphoxide and the silylating reagents gave a two-phase system in which the derivative was favourably partitioned into the upper layer. Partition coefficients and stabilities of the derivatives were measured, and a g.l.c. method for the analysis of the hexuronic acids was thereby developed. The oximes of the hexuronic acids were studied as alternative derivatives for g.l.c., and their equilibrium compositions and g.l.c. retention times are recorded.
Chromatography, Gas↗
Improved analytical method for the hexuronic acids at the reducing terminals of glycosaminoglycans.
When endo-uronidases act on glycosaminoglycans, the reaction products have hexuronic acid residues at the reducing terminals. An analytical method for hexuronic acids at the reducing terminals was devised for hyaluronate oligosaccharides having hexuronic acid residues at the reducing terminals. The procedure is as follows: Hexuronic acid residues at the reducing terminals of hyaluronate oligosaccharides were tritiated with reduction using NaB[3H]4 and the products were hydrolyzed with trifluoroacetic acid and nitrous acid. As a result, the tritiated and reduced hexuronic acid residues, that is aldonic acids, were liberated from the reducing terminals. After passing them through anion and cation ion-exchange resins, the aldonic acids were lactonized. The lactones were developed on paper chromatography, and their radioactivities determined on the paper. The method is also useful for discrimination between glucuronic acid and iduronic acid at the reducing terminals of glycosaminoglycans.
Chromatography, Paper↗
A gas chromatographic method for the quantitative determination of hexuronic acids in alginic acid.
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Alginates↗
The relationship of serum hexuronic acid and monosaccharide levels to urinary free cortisol and cortisone excretion in healthy subjects and in patients with diabetes mellitus and atherosclerotic peripheral vascular disease.
The relationship of hexuronic acid and monosaccharide concentrations in serum to the excretion of urinary free cortisol and cortisone was studied in 14 healthy subjects, in 16 patients with diabetes mellitus, and in 14 patients with atherosclerotic peripheral vascular disease. In both groups of patients increased values of hexuronic acids, reducing monosaccharides and keto-sugars were registered. In diabetics the relative proportion of monosaccharides was increased, the proportion of hexuronic acids was lowered. In atherosclerotic peripheral vascular disease a significant preponderance of hexuronic acid and keto-sugar amounts in the composition of total sugar components was observed in comparison with healthy subjects. In healthy subjects there is a close correlation of urinary free cortisol and cortisone with reducing monosaccharides in blood, measured on the same day. In diabetes not any correlation of the increased values of free corticoids with the sugar components was registered. In atherosclerotic peripheral vascular disease a highly significant correlation between urinary free cortisol and cortisone and the hexuronic acid content in serum was observed. In patients with atherosclerotic peripheral vascular disease the results suggest an altered metabolism of glucose, which is shunted into insulin-insensitive glucuronate pathway in conditions of endogenous hypercortisolism.
Adult↗
Structural identification of isomeric O-trimethylsilyl derivatives of some hexuronic acids.
The structures of the isomeric products obtained on trimethylsilylation of naturally occurring hexuronic acids and their sodium salts and lactones have been established by the application of n.m.r. (for anomeric configuration) and mass spectrometry (for ring size). The equilibria of some of the hexuronic acids in methyl sulphoxide involved a larger proportion of furanoid forms than those in water or pyridine. The proportion of furanoses was also increased by the addition of hexamethyldisilazane. Kinetic evidence indicated that two molecules of each hexuronic acid interacted autocatalytically during mutarotation.
Hexuronic Acids↗
[Content of hexuronic acids, hexoses and tyrosine in the lung tissue in experimental pneumoconiosis].
Content of hydroxyproline, thyrosine, hexuronic acids, hexoses and dry weight of lungs were studied in animals with pneumoconiosis, caused by various agents: two types of silicosis, induced by crystalline and condensed modifications of silica, and anthracosis, caused by anthracite. The data obtained showed that in all the types of pneumoconiosis dry weight of defatted lungs was increased with simultaneous increase of hydroxyproline content in the tissue. The more pronounced alterations were observed in silicosis. In all the types of pneumoconiosis within the experimental period content of hexuronic acids was higher in impaired animals as compared with control ones; the increase in content of hexuronic acids preceded the accumulation of hydroxyproline. Content of hexoses and thyrosine was distinctly increased within 2 days, which apparently correlated with the processes of exudation. Then it was decreased and at the later steps of the impairment amount of hexoses and thyrosine was shown to increase with simultaneous accumulation of hydroxyproline. Dynamics of accumulation of non-collagen components of connective tissue in lungs depended upon the type of a dust to which the animals were exposed.
Animals↗
Modified procedures for the determination of hexuronic acids, hexoses and proteins using the Auto Analyzer II system.
Previous automated procedures for the determination of hexuronic acids, hexoses and proteins have been modified to suit the Technicon Auto Analyzer II system. The present methods were highly reproducable and the detection limits showed to be in the order of 10 micrograms/l (hexuronic acids and hexoses) and 60 micrograms/l (protein) when 0.13--0.34 ml of the sample was used.
Autoanalysis↗
Hexuronic acid dehydrogenase of Agrobacterium tumefaciens.
Growth of Agrobacterium tumefaciens on d-glucuronic acid (GlcUA) or d-galacturonic acid (GalUA) induces formation of hexuronic acid dehydrogenase [d-aldohexuronic acid: nicotinamide adenine dinucleotide (NAD) oxidoreductase]. The dehydrogenase, which irreversibly converts GlcUA or GalUA to the corresponding hexaric acid with the concomitant reduction of NAD, but not of nicotinamide adenine dinucleotide phosphate was purified 60-fold by MnCl(2) treatment, (NH(4))(2)SO(4) fractionation, chromatography on diethylaminoethyl Sephadex and negative adsorption with Ca(3)(PO(4))(2) gel. The pH optimum is 8.0. Other uronic acids, aldohexoses, aldopentoses, and polyols, are not substrates. Reduced nicotinamide adenine dinucleotide is an inhibitor strictly competitive with NAD. Kinetic data indicate that the dehydrogenase induced by growth on GlcUA may not be identical with that induced by growth on GalUA.
Glucuronates↗
Isolation and characterization of the unusual lipopolysaccharide component, 2-amino-2-deoxy-2-N-(27-hydroxyoctacosanoyl)-3-O-(3-hydroxy- tetradecanoyl)-gluco-hexuronic acid, and its de-O-acylation product from the free lipid A of Rhizobium trifolii ANU843.
Two new, unusual lipid A components have been isolated and characterized from the free lipid A of Rhizobium trifolii ANU843. 2-Amino-2-deoxy-2-N-(27-hydroxyoctacosanoyl)-3-O-(3-hydroxy- tetradecanoyl)-gluco-hexuronic acid and its de-O-acylation product were purified from the chloroform/methanol extract of a mild acid hydrolysate of the lipopolysaccharide by chromatography on C18 reverse-phase columns and layers. The compositions of the two compounds were determined by releasing the acyl components by exhaustive acid-catalyzed methanolysis and identifying them as their methyl esters by gas chromatography and gas chromatography/mass spectrometry. The sugar component was identified by converting it to the alditol acetate derivative of glucosamine in a two-step reduction and identifying it as such by gas chromatography/mass spectrometry. The linkages of the fatty acyl components to the sugar residue and the configuration of the sugar component was confirmed by 1H and 13C NMR spectroscopy. The complete structures of the two compounds were further confirmed by fast atom bombardment mass spectrometry. It is still unsure whether the de-O-acylated derivative was formed from the di-acyl compound by de-O-acylation during acid hydrolysis. These structures represent the first report of 2-amino-2-deoxy-gluco-hexuronic acid in the free lipid A of a Gram-negative bacterium and confirms our earlier contention (Hollingsworth, R.I., and Carlson, R. W. (1989) J. Biol. Chem. 264, 9000-9303) of the involvement of 27-hydroxyoctacosanoic acid in the structure of the lipopolysaccharide of Rhizobium trifolii ANU843.
Acylation↗
The short-term effect of cortisol, dexamethasone and ACTH administration on the serum levels of hexuronic acids and monosaccharides in man.
The levels of serum monosaccharides (SMO) and hexuronic acids (SHA) were measured in subjects without any metabolic or endocrine disease after a short-time administration of cortisol, dexamethasone and ACTH. The effects of the three hormones were evaluated in regard to the urinary excretion of free cortisol and cortisone at basal conditions. In thirteen subjects a significant increase of SMO during cortisol treatment was registered after 24 hours. A distinct difference in the response of SMO to cortisol treatment was observed in patients with normal or increased cortisol excretion, respectively. In the subjects with high urinary free corticoids a peak of SMO occurred soon after 4 hours after cortisol administration, in the next 48 hours no tendency of return towards basal levels was observed. In the subjects with normal urinary free cortisol excretion only a slight increment was seen after 24 hours. Soon after 4 hours in eight subjects dexamethasone administration resulted in an increase of SMO without regard to the excretion of urinary free corticoids. The highest values were obtained after 28 hours of dexamethasone treatment. Ten hours after cessation of dexamethasone the levels of SMO reached the basal values. In the study in which ACTH was administered, an increment of SMO was registered only in the first four hours. In the group of subjects treated with ACTH a slight difference between subjects with normal and increased corticoid excretion was seen. The levels of SHA successively increased after the administration of all three hormones, without regard to the basal excretion of urinary free corticoids. This increase persisted also 10 hours after cessation of cortisol and dexamethasone, and 40 hours after the last dosis of ACTH, respectively. The possibility of an altered metabolism of glucose through the glucuronate pathway under conditions of glucocorticoid excess is discussed.
Adrenocorticotropic Hormone↗
The occurrence of three isoforms of heparan sulfate 6-O-sulfotransferase having different specificities for hexuronic acid adjacent to the targeted N-sulfoglucosamine.
We previously cloned heparan sulfate 6-O-sulfotransferase (HS6ST) (Habuchi, H., Kobayashi, M., and Kimata, K. (1998) J. Biol. Chem. 273, 9208-9213). In this study, we report the cloning and characterization of three mouse isoforms of HS6ST, a mouse homologue to the original human HS6ST (HS6ST-1) and two novel HS6STs (HS6ST-2 and HS6ST-3). The cDNAs have been obtained from mouse brain cDNA library by cross-hybridization with human HS6ST cDNA. The three cDNAs contained single open reading frames that predicted type II transmembrane proteins composed of 401, 506, and 470 amino acid residues, respectively. Amino acid sequence of HS6ST-1 was 51 and 57% identical to those of HS6ST-2 and HS6ST-3, respectively. HS6ST-2 and HS6ST-3 had the 50% identity. Overexpression of each isoform in COS-7 cells resulted in about 10-fold increase of HS6ST activity. The three isoforms purified with anti-FLAG antibody affinity column transferred sulfate to heparan sulfate and heparin but not to other glycosaminoglycans. Each isoform showed different specificity toward the isomeric hexuronic acid adjacent to the targeted N-sulfoglucosamine; HS6ST-1 appeared to prefer the iduronosyl N-sulfoglucosamine while HS6ST-2 had a different preference, depending upon the substrate concentrations, and HS6ST-3 acted on either substrate. Northern analysis showed that the expression of each message in various tissues was characteristic to the respective isoform. HS6ST-1 was expressed strongly in liver, and HS6ST-2 was expressed mainly in brain and spleen. In contrast, HS6ST-3 was expressed rather ubiquitously. These results suggest that the expression of these isoforms may be regulated in tissue-specific manners and that each isoform may be involved in the synthesis of heparan sulfates with tissue-specific structures and functions.
Amino Acid Sequence↗
Substrate specificity of the heparan sulfate hexuronic acid 2-O-sulfotransferase.
The interaction of heparan sulfate with different ligand proteins depends on the precise location of O-sulfate groups in the polysaccharide chain. We have previously shown that overexpression in human kidney 293 cells of a mouse mastocytoma 2-O-sulfotransferase (2-OST), previously thought to catalyze the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate to C2 of L-iduronyl residues, preferentially increases the level of 2-O-sulfation of D-glucuronyl units [Rong, J., Habuchi, H., Kimata, K., Lindahl, U., and Kusche-Gullberg, M. (2000) Biochem. J. 346, 463-468]. In the study presented here, we further investigated the substrate specificity of the mouse mastocytoma 2-OST. Different polysaccharide acceptor substrates were incubated with cell extracts from 2-OST-transfected 293 cells together with the sulfate donor 3'-phosphoadenosine 5'-phospho[(35)S]sulfate. Incubations with O-desulfated heparin, predominantly composed of [(4)alphaIdoA(1)-(4)alphaGlcNSO(3)(1)-](n)(), resulted in 2-O-sulfation of iduronic acid. When, on the other hand, an N-sulfated capsular polysaccharide from Escherichia coli K5, with the structure [(4)betaGlcA(1)-(4)alphaGlcNSO(3)(1)-](n)(), was used as an acceptor, sulfate was transferred almost exclusively to C2 of glucuronic acid. Substrates containing both iduronic and glucuronic acid residues in about equal proportions strongly favored sulfation of iduronic acid. In agreement with these results, the 2-OST was found to have a approximately 5-fold higher affinity for iduronic acid-containing substrate disaccharide units (K(m) approximately 3.7 microM) than for glucuronic acid-containing substrate disaccharide units (K(m) approximately 19.3 microM).
Animals↗
[Hexuronic acid content of the blood proteins].
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Ascorbic Acid↗
[A manometric method for the determination of hexuronic acids].
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Hexuronic Acids↗