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↗
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↗
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↗
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↗
A partial modification of the carbazole method of Bitter and Muir for quantitation of hexuronic acids.
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Borates↗
Determination of hexuronic acids in glycosaminoglycans by automated ion-exchange chromatography.
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Animals↗
Evidence for degradation of heparan sulfate by endoglycosidases: glucosamine and hexuronic acid are reducing terminals of intracellular heparan sulfate from human skin fibroblasts.
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Animals↗
Study on the factors yielding high color in the carbazole reaction with hexuronic acid-containing substances.
The color yields with hexuronic acids and hexuronic acid-containing substances were studied by means of the carbazole method of Bitter and Muir with or without 0.025 M borate. The carbazole-borate to carbazole (CB/C) ratios thus obtained indicated not only the degree of the borate effects on the color yields with these materials but also the anomalous nature of some of these substances in the carbozole reaction. The present data indicate that the high color yield with heparin in the carbozole reaction may be due to the production of free amino groups from acid-labile sulfamino groups in the early stage of the reaction, resulting in suppression of protonation on the alpha-D-glucosaminidic oxygen atoms attached to the hexuronic acid residues in the molecule. Moreover, it is suggested that the degree of the unusual color yields in the carbazole reaction with glycosaminoglycans is greatly influenced by the anomeric configuration of the hexosaminyl linkages attached to the hexuronic acid residues in these polymers.
Carbazoles↗
Some chemical characteristics of human minor salivary gland secretions.
The minor salivary glands contribute to the composition of whole saliva, but little information has been available about their chemical constituents. Pilocarpine-stimulated labial and palatine secretion from 4 human subjects was investigated by paper and disc electrophoresis, immunochemical analysis, and for content of carbohydrates, amino acids, lipids, hexuronic acids and sulphate. No significant differences were noted between the labial and palatine secretions by any of the methods employed. The minor gland secretions appeared to consist mainly of mucosubstances, possibly with blood group specificity. In addition, three water-soluble components with the characteristics of albumin, alpha-amylase and secretory IgA were seen. The minor gland secretions had an amino acid profile different from those of the major salivary glands and contained higher proportions of carbohydrate. Only one lipid component, with the characteristics of a polar lipid, was seen. Hexuronic acids were not detected in either secretion, whereas both contained sulphate. It would appear that the minor mucous glands contribute to the content of mucosubstances in whole saliva, whereas their content of water-soluble material is negligible in this respect.
Adult↗
Connective tissue constituents of the fowl. Effects of exogenous estrogen.
The levels of connective tissue constituents (hexosamine, hexuronic acid, hexose and hydroxyproline) and the composition of isolated mucopolysaccharide-peptide complexes were determined in some organs and tissue of male and female fowl treated and not treated with estradiol-17beta. Most of the changes occurred in the male. Estrogen administration brought statistically significant increases in the contents of hexosamine and hexuronic acid in the cartilage of the male and of hexose in the spleen of both males and females. It also increased the hydroxyproline in the testis and in the cartilage of the male. Estrogen decreased the content of hexosamine in the combs of both males and females, and in the wattle of the female, of hexuronic acid, hexose and hydroxyproline in the liver of the male, and hydroxyproline in the breast muscle of the male. Hexosamine, sialic acid, lipid and protein contents of blood sera of estrogenized birds were substantially higher than that of the controls. Gas liquid chromatography of the lipids of the tissues indicated that estrogen administration brought about an increase in the proportion of the unsaturated fraction to the total fatty acid content.
Animals↗
Isolation and characterization of a high molecular weight glycoprotein from human blood platelets.
A high molecular weight glycoprotein consisting of three disulfide-linked 142,000 molecular weight chains has been isolated from human blood platelets. The glycoprotein, designated thrombospondin, is released by platelets in response to thrombin treatment and is proteolyzed when left in the presence of platelets after liberation. It is relatively insensitive to degradation by thrombin. Thrombospondin is a filamentous protein of dimensions approximately 7 X 70 nm and contains 1.9% neutral sugars, 1.4% amino sugars, 0.7% sialic acid, and no hexuronic acid. Amino acid analysis reveals that the level of cysteine is approximately 260 residues per molecule. Thrombospondin binds to immobilized heparin but is released by 0.45 M sodium chloride. A single band is obtained by isoelectric focusing, indicating a pI of 4.7 as well as a relatively high degree of purity. Degradation of the intact molecule with trypsin yields a stable core particle of molecular weight 210,000 comprised of three 70,000 chains.
Alkylation↗
The removal of non-collagen components from newborn calf dermis with magnesium chloride solution.
1. Non-collagenous substances in newborn calf dermis were extracted with solutions of various concentrations of MgCl2. The total protein and hydroxyproline contents in MgCl2 extracts increased with increase in the concentration of MgCl2 in the solutions. In particular, steep increases of their contents were observed at concentrations of MgCl2 from 0.5 to 1.0 M. Total amounts of hydroxyproline in 1.0, 2.0, and 3.0 M MgCl2 extracts were equivalent to 40-50% of the hydroxyproline content in the whole connective tissue. Hexose and hexosamine contents of MgCl2 extracts increased with increase of the MgCl2 concentration. Hexuronic acid was hardly present in the residues after extractions with 0.5, 1.0, 2.0, and 3.0 M MgCl2. 2. Plasma proteins, hyaluronic acid, and dermatan sulfate were extracted at low concentrations of MgCl2. A non-collagenous protein and MgCl2-soluble collagen were extracted with 1.0, 2.0, and 3.0 M MgCl2 solutions. The disperson of collagen fibrils was observed in the residue extracted with 1.0 M MgCl2 solution by electron microscopy; the fibril structure of collagen was disordered by extraction with 2.0 and 3.0 M MgCl2. The results suggest that the dispersion and disorder of collagen fibrils lead to the release of a non-collagenous protein. Furthermore, it is suggested that the removal of hyaluronic acid and dermatan sulfate was not very effective for the solubilization of a large amount of collagen, but was suitable as a pretreatment to the extraction of a non-collagenous protein accompanied by the solubilization of a large amount of collagen. 3. The non-collagenous protein was purified by DEAE-cellulose column chromatography. Polyacrylamide gel electrophoresis of this protein at pH 8.5 showed a single band moving to the cathode. The non-collagenous protein contained 3.7% hexose, 1.8% hexosamine, and no hexuronic acid. This protein is rich in glycine, glutamic acid, and alanine, and contains neither hydroxyproline nor hydroxylysine. Sedimentation analysis showed a single peak with 1.8 S and the molecular weight was approx. 43,000 as determided by SDS polyacrylamide gel electrophoresis.
Amino Acids↗
Bilirubin conjugates in bile of man, rat and dog. Semi-quantitative analysis of bile composition by thin-layer chromatography.
1. Conjugated bile pigments, separated in two fractions by semi-quantitative t.l.c. performed on silicic acid with phenol/water as the developing solvent, were treated with diazotized ethyl anthranilate. Resulting dipyrrylazo derivatives were analysed by quantitative t.l.c. 2. The tentative structure elucidation of tetrapyrrolic bilirubin conjugates and semi-quantitative evaluation of rat bile, post-obstructive human bile and dog bile composition is presented. 3. Homogeneous and mixed hexuronic acid diesters of bilirubin containing glucuronic acid constitute 51% of the total conjugates in normal rat bile, 45% of those in human post-obstructive bile and 38% of those in obstructed rat biles. 4. Monoconjugated bilirubin amounts to 33% of total conjugated bile pigments in normal rat bile, and 17 and 14% in post-obstructive hepatic human bile and gall-bladder bile of dog respectively. After loading with unconjugated bilirubin a greater amount of monoconjugates (56%) occur in the rat bile, whereas bilirubin diglucuronide excretion is decreased (34%). 5. In gall-bladder bile of normal dog, 40% of glucose-containing diconjugates, 32% of homogeneous and/or mixed hexuronic acid (mainly glucuronic acid) diesters of bilirubin and 14% of xylose-containing diconjugates are estimated. 6. Increased amounts of bilirubin conjugates, including some with unidentified uronic acid groups, were observed in cholestatic rat biles and quantities of conjugates with glucuronic acid were decreased.
Animals↗
Metabolism and proliferation of L929 mouse fibroblasts cultured in the presence of sodium fluoride.
L 929 mouse fibroblasts were cultured as monolayers with different amounts of sodium fluoride, corresponding to those used therapeutically. Proliferation of the cells was inhibited in the logarithmic phase of cell growth. There was no change in the protein concentration in the cells, but the concentration of hydroxyproline containing substances in the cells increased while that of hexuronic acid containing substances decreased. The changes in proliferation and in the concentrations of hydroxyproline containing substances and hexuronic acid containing substances were statistically significant. Although the findings cannot be explained in detail it can be concluded that at therapeutic concentrations sodium fluoride has a definite action in contact with the fibroblast, the typical connective tissue cell. This dose dependant action corroborates clinical experience.
Animals↗
Nearest neighbor analysis of heparin: identification and quantitation of the products formed by selective depolymerization procedures.
Heparin was carboxyl-reduced with sodium boro[3H]hydride and converted to a mixture of oligosaccharides by treatment with nitrous acid at pH 2. The oligosaccharide mixture was aldehyde-reduced with sodium boro[3H]hydride and the mixture of products, labeled both in the hexoses formed in the carboxyl-reduction step and in the reducing sugars formed in the nitrous acid reaction, was separated and analyzed. The major product, L-idosyl 2-sulfate leads to anhydro-D-mannitol 6-sulfate (I), contained 60% of hexoses derived from the hexuronic acid residues in the original heparin. A second product, which contained 15% of the hexoses derived from the hexuronic acid residues in the original heparin, was identified as a tetrasaccharide composed of two L-idosyl 2-sulfate residues, one anhydro-D-mannitol 6-sulfate residue (the reducing end),and a hydroxymethylpentose sulfate residue formed by deamination of a disulfated D-glucosamine residue without bond cleavage. Several additional disaccharides derived from the regions of the polymer which contained D-glucuronic acid residues and lower degrees of O-sulfation were also identified among the deamination products. The oligosaccharides that were obtained accounted for 100% of the original carboxyl-reduced heparin, and paper chromatographic profiles of the oligosaccharide separations can be used as a fingerprint of the heparin preparation. The properties of I were examined in greater detail. The glycosidic bond of the L-idosyl 2-sulfate residue was found to be extremely labile to 0.1 N HCl at 100 degrees C, hydrolyzing with a t 1/2 of 18 min to give high yields of L-idose 2-sulfate and anhydro-D-mannitol 6-sulfate. L-Idofuranose was also identified as an intermediate in the conversion of L-idose 2-sulfate to L-idosan. The acid lability of the L-idosyl 2-sulfate bond in I offers a new route for the selective cleavage of carboxyl-reduced heparin.
Animals↗
The effects of menadione, ethyl biscoumacetate, and sodium salicylate on the metabolism of mucopolysaccharides in the aortic wall and liver of rats.
In rats with hyper- and hypovitaminosis the contents were determined of acid mucopolysaccharides (MPS) on the basis of contents of hexuronic acids; the total contents of biopolymers containing hexosamines (acid MPS, glycoproteins), on the basis of contents of hexosamines in the aortic wall and in the liver; and the activity of glutamine-fructose-6-phosphate aminotransferase (GPAT; EC 2.6.1.16) in the liver. Menadione-induced K hypervitaminosis was accompanied by moderate elevations of indicators of MPS metabolism. Protracted administration of ethyl biscoumacetate or sodium salicylate lowered the contents of acid MPS and of biopolymers containing hexosamines in the aortic wall and in the liver. Simultaneously, the GPAT activity in the liver markedly decreased.
Animals↗