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PubMed1996

A lipid A analog inhibits LPS-induced cytokine expression and improves survival in endotoxemic mice.

It has recently been shown that inactive disaccharidic analogs of lipid A, an essential structure of lipopolysaccharide (LPS), may act as LPS antagonists which would be effective against septic shock induced by gram-negative bacteria endotoxin. In the present study we examined the inhibitory effect of DY-9973, a synthetic monosaccharidic lipid A analog, on LPS-induced cytokine expression in macrophages and lethal toxicity in mice. DY-9973 inhibited TNF-alpha production induced by LPS in human monocytes and monoblastic U937 cells. Expression of cytokine mRNAs such as TNF-alpha and IL-1 beta induced by LPS was inhibited by treatment with DY-9973 in U937 cells. Meanwhile, DY-9973 did not inhibit IL-1 beta-induced TNF-alpha production in U937 cells. TNF-alpha production induced by LPS or IL-1 beta was similarly inhibited by treatment with herbimycin, a tyrosine kinase inhibitor. Pretreatment with DY-9973 inhibited the elevation of serum TNF-alpha activity induced by the injection of LPS and reduced the lethal toxicity of LPS in BCG-primed mice. These results suggest that monosaccharidic lipid A analog such as DY-9973 can inhibit LPS-induced activation of macrophages and that it reduces lethal toxicity of LPS.

Animals↗
PubMed1981

Sugar residues on proteins.

Glycoproteins have become increasingly important in the structure and function of many different mammalian systems; for example, membrane glycoproteins and glycoprotein hormones. It is, therefore, important to understand their chemistry, which would include an understanding of both the carbohydrate and protein parts of the molecule. Since the chemical characterization of the protein moiety has been extensively examined and the techniques for its characterization are well worked out, only the carbohydrate portion of glycoproteins will be reviewed in this article. The chemical nature of the carbohydrate moiety of glycoproteins will be examined. First, the types of monosaccharides present in animal systems, especially those in the mammalian systems, will be described. Next, various types of simple and complex carbohydrate chains will be discussed to establish the diversity, size, and number of chains present in the carbohydrate units in different glycoproteins. Then, the type of linkages of the carbohydrate to the protein will be examined to determine if the primary sequence of protein is important in determining the size and type of carbohydrate chains present in glycoproteins. Finally, the current methods of structural elucidation such as monosaccharide sequence, intersugar bonds, and anomeric linkages in the carbohydrate moiety of glycoproteins will be reviewed. These methods include the techniques of periodate oxidation, methylation, partial acid hydrolysis, and specific glycosidase digestion of glycoproteins, as well as the latest techniques using micromethods of carbohydrate quantitation and characterization involving gas chromatography and mass spectrometry. The function of the carbohydrate in glycoproteins will also be considered. First, hormone glycoproteins will be discussed in their relationship to the immunological and biological function of the glycoprotein when the carbohydrate is sequentially removed. Next, the function of the carbohydrate in the turnover of glycoproteins will be discussed. These topics will be considered in order to develop an understanding of a specific function(s) of the carbohydrate in glycoproteins.

Amino Acid Sequence↗
PubMed1986

In vitro fermentation of sugars, grains, and by-product feeds in relation to initiation of ruminal lactate production.

In vitro fermentations of various sugars, grains, and by-products were conducted to investigate the relationships between soluble carbohydrates and initiation of ruminal lactate production. Fermentation of hexose sugars, both monosaccharides and disaccharides, resulted in greater accumulation of lactate than did fermentation of pentoses. Results of fermentation of grains and by-products, in order of greatest to least potential to produce lactic acid, were steam-flaked barley = barley = wheat greater than moisture corn = sorghum grain. Water-soluble fractions of the grains and by-products were more rapidly fermented to lactate than the insoluble fractions. Combining 10% soluble fractions from wheat, barley, and steam-flaked barley with 90% insoluble fractions from corn resulted in significant increases in lactate concentration. Analysis of sugar composition of these water soluble materials indicated that monosaccharides and disaccharides constitute 23 to 46% by weight. Data suggest that water-soluble materials play a role in initiation of lactate production from grains, and further production is dependent on starch fermentability.

Animal Feed↗
PubMed1992

Variations and distributions of O-glycosidically linked sugar chains in bovine kappa-casein.

The variation and distribution of O-glycosidically linked sugar chains in kappa-casein from bovine mature milk were analyzed by HPLC, fast atom bombardment mass spectrometry, and 13C nuclear magnetic resonance. A monosaccharide alditol (N-acetylgalactosaminitol) and four oligosaccharide alditols [a neutral disaccharide (galactosyl-beta 1-3N-acetylgalactosaminitol), two acidic trisaccharides (straight chain: N-acetylneuraminyl alpha 2-3galactosyl-beta 1-3N-acetylgalactosaminitol and branch chain: galactosyl beta 1-3(N-acetylneuraminyl alpha 2-6)N-acetylgalactosaminitol), and an acidic tetrasaccharide(N-acetylneuraminyl alpha 2-3galactosyl-beta 1-3(N-acetylgalactosaminyl alpha 2-6)N-acetylgalactosaminitol] were identified as sugar chains linking on normal bovine kappa-casein. The most dominant sugar chain was an acidic tetrasaccharide. The four oligosaccharide chains were identical to those already found, but N-acetylgalactosamine was a newly identified sugar chain linking on kappa-casein. The distribution of monosaccharide, disaccharide, trisaccharide (straight), trisaccharide (branched), and tetrasaccharide chains were determined by HPLC to be .8, 6.3, 18.4, 18.5, and 56.0%, respectively (means of five kappa-caseins).

Animals↗
PubMed1998

Inhibition of insulin release by alpha- and beta-D-galactose pentaacetate.

Several monosaccharide polyacetate esters display higher biological efficiency than the corresponding unesterified carbohydrates, this being attributable to their capacity to cross the plasma membrane without requiring the intervention of a specific carrier system and to their subsequent intracellular esterase-catalyzed hydrolysis. Some of these esters, however, also exert a direct effect upon a receptor system apparently displaying analogies with that involved in the identification of bitter compounds by taste buds. For instance, under suitable experimental conditions, esters of non-nutrient monosaccharides, such as L-glucose, D-mannoheptulose or 2-deoxy-D-glucose, unexpectedly stimulate insulin release. The present work reveals that alpha-D-galactose pentaacetate and, to a lesser extent, beta-D-galactose pentaacetate both inhibit leucine-induced insulin release in rat pancreatic islets. This indicates that the postulated receptor system displays anomeric specificity and may participate in a negative modulation of insulin secretion. It is proposed that advantage could be taken of the negative insulinotropic action of D-galactose pentaacetate esters to prevent excessive insulin release in pathological situations.

Animals↗
PubMed1998

Enzyme array-amperometric detection in carbohydrate analysis.

The introduction of an enzyme array-electrochemical detection method for carbohydrate analysis is demonstrated by using two complex and one high mannose N-linked oligosaccharides. Instead of measuring the remaining uncleaved oligosaccharides in enzymatic digestion, released monosaccharides are directly quantified by pulsed amperometric detection at a gold electrode. The measured monosaccharide concentrations in combination with the enzyme array analysis provide structural characterization of oligosaccharides. The enzyme array-electrochemical detection method does not require any separation procedure or any prior labeling of oligosaccharides. However, this method is limited by the use of purified oligosaccharide samples and the nature of the enzyme array. The development of more sophisticated enzyme arrays relies upon the introduction of a bank of highly specific (bond, arm, aglycon) exoglycosidases.

Carbohydrate Metabolism↗
PubMed1999

D-glucose increases the synthesis of tissue-type plasminogen activator (t-PA) in human peritoneal mesothelial cells.

Physical and chemical irritation of the peritoneum through glucose-based hyperosmolar dialysis solutions results in a nonbacterial serositis with fibrinous exudation. Thereby, human peritoneal mesothelial cells (HMC) play an important role in maintaining the balance between the peritoneal generation and degradation of fibrin by expressing the fibrinolytic enzyme tissue-type plasminogen activator (t-PA) as well as the specific plasminogen activator inhibitor-1 (PAI-1). In this study, we analyzed the effect of D-glucose and metabolically inert monosaccharides on the synthesis of t-PA and PAI-1 in cultured HMC. Incubation of HMC with D-glucose or the metabolically inert monosaccharides mannitol and L-glucose (5-90 mM) resulted in a time- and concentration-dependent increase in t-PA mRNA expression and antigen secretion without affecting PAI-1 synthesis. A similar effect was evident when HMC were first exposed sequentially to pooled spent peritoneal dialysis effluent for up to 4 hours, and subsequently incubated for 20 hours in control medium. The stimulating effect of high D-glucose on t-PA expression in HMC was prevented by treating the cells with different protein kinase C (PKC) inhibitors (Ro 31-8220, Gö 6976), but could not be mimicked by the PKC-activating phorbol ester PMA, indicating that this effect of high glucose is dependent on PKC activity, but not mediated through PKC activation. Also, using specific inhibitors (PD 98059, SB 203580) and activators (PMA, anisomycin, IL-1alpha) of the major routes of the mitogen-activated protein kinases (MAPKs) cascade, we found no evidence for a role of this cascade in regulating t-PA expression in HMC. We conclude that hyperosmolarity induces t-PA (but not PAI-1) in HMC via a regulatory mechanism that requires active PKC, but that does not involve a major pathway in the MAPK cascade.

Cells, Cultured↗
PubMed2000

Sequence and structural determinants of mannose recognition.

Mannose, an abundant cell surface monosaccharide binds to a diverse set of receptors, which are involved in a variety of important cellular processes. Structural analysis has been carried out on all the proteins containing non-covalently bound mannose as a monosaccharide in the Protein Data Bank, to identify common recognition principles. Proteins, highly specific to mannose, belonging to the super family of bulb lectins, are found to contain a consensus sequence motif QXDXNXVXY, which has been identified to be essential for mannose binding. Analysis of this motif in the crystal structures of bulb lectins has led to the understanding of the contribution of individual residues in mannose recognition. Comparison with other mannose binding proteins, reveals common hydrogen bonding patterns in all of them, despite differences in sequence, overall fold and the substructures at the binding sites of individual proteins. A database analysis also suggests that although the topology of the backbone, as at the binding site in bulb lectins, can generate mannose binding capability in a few other proteins, sequence and disposition of not only the residues in the motif, but also the residues in the neighborhood play a crucial role in allowing that property to be retained.

Amino Acid Motifs↗
PubMedDate not supplied

[A quantitative method for determining lectin activity on microplates].

A modification of a known quantitative solidphase microtiter plate lectin assay elaborated by Hatakeyama and coauthors developed with biotinylated lectins and ExtrAvidin--alkaline phosphatase conjugate was proposed. The modification was performed in order to use a broad spectra of lectin ligands, including glycopeptides, peptides, etc. The optimal concentrations of the reagents and time of the reagents incubation were selected. Being known from the literature Kdiss for Concanavalin A and monosaccharides: methyl-Man, Man, Glc and Gal were determined in a model experiments. The results were in agreement with the range of monosaccharides specificity for the Concanavalin A. The modification described is relatively simple and sensitive.

Alkaline Phosphatase↗
PubMed1975

Carbohydrate absorption. Studies on the glucose transport by isolated brush border membranes. A contribution towards an understanding of the molecular mechanism of sugar absorption.

From investigations, mainly on intact in vitro preparations of small intestine, it has been established that the epithelial cell carries out digestion as well as absorption of carbohydrates, i.e. the luminal (brush border) plasma membrane contains di- and poly-saccharidases for the degradation of carbohydrates to monosaccharides as well as transport systems for monosaccharides. Recently, an intact glucose transport system has been demonstrated in isolated membranes from rat intestinal brush borders. In the isolated membranes, glucose transport has the characteristics expected for 'facilitated diffusion' of glucose coupled to Na+ translocation. The Na+-dependent uptake of glucose can be influenced by electrical potentials across the brush border membrane, which indicates that the positive charge of Na+, associated with sugar uptake, is not compensated by the counter-movement of another cation, e.g. K+, or by the co-movement of an anion via the same glucose 'carrier'. In other words, the Na+-coupled D-glucose transport is linked to a charge translocation - it is electrogenic. The apparent Na+ independence of glucose transport in vivo and the accumulation of glucose against a glucose as well as a Na+ concentration gradient by isolated epithelial cells may be explained by the 'ion gradient' model of Crane and Schultz and Zalusky provided the electrical membrane potential is high under these conditions and the electrochemical potential of Na+ serves as driving force for 'active' glucose transport.

Animals↗
PubMed2000

Strongyloides ratti: chemotactic responses of third-stage larvae to selected serum proteins and albumins.

Experiments were carried out in vitro to investigate whether the sera of several animals as well as albumins and peptides might act as attractants for larvae of Strongyloides ratti. Samples of sera from several mammal species were dialysed and the aliquots were further centrifuged using ultrafiltration cartridges to remove any remaining small molecules. Additional test substances included commercially obtained ovalbumin, rat and bovine serum albumins, polypeptides such as peptone, tryptone and tryptose, amino nitrogens, monosaccharides, and reduced glutathione (triaminopeptide). Larvae were strongly attracted to the dialysed mammalian sera, which mainly consisted of serum albumin and globulins. Ov- and serum albumins, and polypeptides also acted as attractants. On the other hand, reduced glutathione, 16 kinds of amino acids and four kinds of monosaccharides did not attract this nematode.

Animals↗
PubMed1975

Carbohydrate digestion and absorption in the equine small intestine.

Dietary carbohydrates, which constitute a most important source of equine nutrition, are digested and absorbed by a series of complex processes principally in the small intestine, beginning with intraluminal starch hydrolysis by the action of pancreatic amylase. The continuous secretion of a copious volume of pancreatic juice, low in enzyme activity, presumably releases sufficient oligosaccharides for further hydrolysis at the intestinal cell surface by brush border enzymes. Active carrier mediated mechanisms then transport the final hexose products across the intestinal cell for uptake in the hepatic portal system. Brush border disaccharidase activities in the equine small intestine are of the same order of magnitude, and have a similar distribution pattern, to those reported in omnivorous and carnivorous species. The disaccharidase development patterns are characteristic and reflect the ability of the horse to digest the major nutrient sources adequately at various stages of life. The efficiency of the mucosal disaccharidases and the monosaccharide transport systems in the equine small intestine have been established by a series of oral disaccharide and monosaccharide tolerance tests. Horses older than three years of age are unable to hydrolyse lactose, but young and adult horses are fully capable of rapidly hydrolysing sucrose and maltose loads. Several tests have clinical application for assessing small intestinal dysfunction in the investigation of diarrhoea and malabsorption. The deficient digestion or absorption of carbohydrate, whether primary or secondary, can almost always be localized to a defect in the enzymic or transport capacity of the small intestinal surface cell. The continued ingestion of lactose could be detrimental in severely diarrhoeic foals.

Animals↗
PubMedDate not supplied

[Characteristics of bacterial lipopolysaccharides depending on extraction method].

Carbohydrate-containing biopolymers have been isolated from Erwinia carotovora subsp. atroseptica 549 by two methods--the aqueous-phenol and with using physiological solution--with addition and without addition of ethylenediaminetetraacetate (EDTA). The biopolymers yield from the cells of bacteria are shown to depend on the extraction method. Lipopolysaccharide-protein complex have been isolated by the sparing method. The purest lipopolysaccharide have been isolated by the aqueousphenol method. The preliminary treatment of cells by EDTA increased the biopolymers output. Carbohydrate containing biopolymers isolated from the cells of bacteria by different methods possess the similar qualitative composition of monosaccharides but they differ in the quantitative content of monosaccharides, spectrum of fatty acids of lipid components as well as in the protein content.

Biopolymers↗
PubMed2002

Gas-chromatography/mass-spectrometry analysis of human skin constituents as heptafluorobutyrate derivatives with special reference to long-chain bases.

The composition of the constituents (monosaccharides, long-chain bases, and fatty acids) found in an ethanol extract of the human skin could be determined, without time-consuming steps of purification, after acid-catalyzed anhydrous methanolysis, followed by the formation of volatile derivatives with heptafluorobutyric anhydride and gas-chromatography/mass-spectrometry analysis. Despite the extreme heterogeneity of such extracts, the electron impact analysis of the constituents allowed qualitative and quantitative determinations of monosaccharides, long-chain bases, fatty acids, and alkyl-glycerols. Throughout the different long-chain bases, sphingenines (Sphes), sphinganines, phytosphingosines, and 6-hydroxy-Sphes (6oh-Sphes) can be identified and quantified. Long-chain bases with a chain-length up to 28 carbon atoms can be identified through specific fragmentation patterns in the electron impact mode. Particular attention was drawn to the behavior of compounds of the family of 6oh-Sphes upon acid-catalyzed methanolysis.

Acylation↗
PubMed2003

[Congenital disorders of glycosylation].

Congenital disorders of glycosylation (CDG) is a fast growing group of autosomal recessive inherited diseases caused by defects in glycosylation. The biosynthesis of the glycans is a pathways which occurs in the endoplasmic reticulum and Golgi complex thanks to highly specific enzymes: glycosidases and glycosyltransferases. The sequential addition of monosaccharides needs precursors which are nucleotide sugars or dolichyl sugars. CDG are divided into two groups: CDG I composed of defects in enzymes involved in the assembly of dolicholpyrophosphate oligosaccharide and in the transfer of oligosaccharide from dolicholpyrophosphate to an Asn residue on nascent proteins; CDG II composed of defects in the processing of protein-bound glycans with alterations in enzymes or in the transporters of monosaccharides. Clinical symptoms are poorly specific and multisystemic, biochemistry provides the diagnosis: Isoelectrofocalisation and western blot of serum transferrin and some other glycoproteins; Measurement of enzyme activities; Research of gene mutations. Today, thirteen CDG are identified, the most frequent is CDG Ia due to a defect in the phosphomannomutase activities and CDG Ib due to a defective phosphomannose isomerase, is the only CDG which is successfully treated with mannose.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1992

Ligand binding characteristics of the major mistletoe lectin.

Carbohydrate binding specificity of the galactose-specific, major lectin of mistletoe extract (ML-1) was studied by an inhibition assay using monosaccharides, monosaccharide derivatives, disaccharides, and compounds containing multiple galactosyl terminals. The results indicate that 1) both alpha- and beta-galactosyl residues are recognized equally well; 2) each of the hydroxyl groups of galactose contributes to varying degrees to the binding process, the 4-OH being the most important and the 6-OH the least important hydroxyl group; 3) disaccharide sequences of Gal beta 2Gal and Gal beta 3Gal have much higher affinity than galactose, whereas affinity of all other Gal-disaccharides is only slightly better than galactose; 4) macromolecular ligands having 10 or more terminal galactosyl residues have 500-fold higher affinity than Gal; and 5) a group on ML-1 with pK alpha of 4.8 appears to be involved in the binding of ligand.

Binding Sites↗
PubMed1992

Influence of pH and phosphate ions on the kinetics of enolisation and degradation of fructosamines. Studies with the model fructosamine, N epsilon-1-deoxy-D-fructos-1-yl-hippuryl-lysine.

Investigation of the rate of enolisation and degradation of the model peptide fructosamine N epsilon-1-deoxy-D-fructos-1-yl-hippuryl-lysine and related monosaccharides revealed the fructosamine to be activated towards enolisation but little of the enolic intermediates proceeded to form advanced glycation endproducts. For the oxidative degradation of monosaccharides, enolisation was rate-limiting. Enolisation of the fructosamine was promoted by hydroxide, phosphate and pyrophosphate buffer ions but not directly influenced by the protonation state of the fructosyl amino group. The formation of advanced glycation end-products may be greatly enhanced in the presence of suitable catalysts (trace metal ions) of the degradation of fructosamine-derived enolic intermediates.

Anions↗
PubMed1992

Characterization of a series of novel fucose-containing glycosphingolipid immunogens from eggs of Schistosoma mansoni.

Lipid extracts of eggs, worms, and cercariae of the parasitic trematode Schistosoma mansoni have been shown to contain a large number of highly immunogenic glycolipids (Weiss, J. B., Magnani, J. L., and Strand, M. (1986) J. Immunol. 136, 4275-4282). Three fractions of schistosome egg glycolipids were selected on the basis of their reactivity with an anti-schistosome monoclonal antibody (128C3/3), which recognizes a developmentally regulated carbohydrate epitope present on both glycolipid and glycoprotein antigens from S. mansoni. These fractions were purified by silica gel chromatography and preparative high performance thin layer chromatography and characterized by monosaccharide, fatty acid, and linkage analysis with gas chromatography-mass spectrometry, as well as by positive and negative ion fast atom bombardment-mass spectrometry. The immunogens were shown to be glycosphingolipids having homologous structures based on a highly novel extension of glucosylceramide. Monosaccharide inhibition studies indicated that the epitope recognized by 128C3/3 residues in an outer region of the immunogens consisting of Fuc2GlcNAc (where Fuc is fucose) repeating units. The largest antigen characterized may have the following structure, based on the evidence presented in this paper. [sequence: see text] The evidence indicated the existence of a series of glycan structures created by deletions of one or more Fuc1----3 side chains from the above structure.

Animals↗