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At least 253 records · Page 14Linked to original sources
PubMed1980

Biosynthesis of mammary glycoproteins. Partial characterization of the sequence for the assembly of lipid-linked saccharides.

Incubation of a membrane preparation from the lactating bovine mammary gland with UDP-[3H]GlcNAc, GDP-[14C]Man, and UDP-[3H]Glc results in the biosynthesis of 15 lipid-linked saccharides that differ from one another by a monosaccharide unit. Pulse and chase kinetics indicate that these glycolipids are related to one another as precursor products for the biosynthesis of asparagine-linked glycoproteins of this tissue. [Man-14C]- and [Man-14C, GlcNAc-3H]saccharides were prepared from corresponding glycolipids by mild acid hydrolysis. Following extensive purification by paper and gel filtration chromatography, structural characterization was conducted on tri-, tetra-, penta-, and undecasaccharides via size determination on calibrated columns of Bio-Gel P-2 and P-4, compositional analysis, exo- and endoglycosidase digestions, methylation, Smith degradation, and acetolysis. These structures were identified as: Man beta 1 leads to 4(3)GlcNAc beta 1 leads to 4(3)Glc-NAc, Man alpha 1 leads to 3Man beta 1 leads to 4(3)GlcNAc beta 1 leads to 4(3)GlcNAc, Man alpha 1 leads to 3(Man alpha 1 leads to 6)Man beta 1 leads to 4(3)Glc NAc beta 1 leads to 4(3)Glc-NAc, and Man alpha 1 leads to 2 Man alpha 1 leads to 2Man alpha 1 leads to 3(Man alpha 1 leads to 2Man alpha 1 leads to 6[Man alpha 1 leads to 2Man alpha 1 leads to 3]Man alpha 1 leads to 6)Man beta 1 leads to 4(3)GlcNAc beta 1 leads to 4(3)GlcNAc.

Animals↗
PubMed1984

Trypanosoma (Nannomonas) congolense: analysis by fluorescein-conjugated plant lectins of surface saccharides of cloned variant antigen types differing in infectivity for mice.

Surface saccharides of 4 cloned VATs (variant antigen types) of Trypanosoma (Nannomonas) congolense, AmNats (Amherst Nannomonas antigen types) 1.1, 1.2, 2.1, and 3.1, derived from 3 different stocks, were compared by fluorescein-conjugated, plant lectins using a quantitative fluorescence method. It was ascertained by the ID63 assay that the 4 AmNats differed in their infectivity for mice. The lectins employed for AmNats 1.1, 2.1, and 3.1 were concanavalin A (Con A), wheat germ agglutinin (WGA), soybean agglutinin (SBA), garden pea agglutinin (GPA), and gorse seed (Ulex europaeus) agglutinin (UEA). In view of the results obtained with these 3 AmNats, only Con A, WGA, and GPA were used with AmNat 1.2, which was isolated after the lectin analyses of the other cloned VATs were completed. On the basis of experimental results, we concluded that the amounts of saccharide residues binding the several lectins differed among the 4 AmNats. In each instance, the reaction specificity was controlled by inclusion of an appropriate sugar in the incubation mixture. Although the actual numbers of various specific lectin-binding sites differed among the AmNats 1.1, 2.1, and 3.1, all of them were found to have the following sugars on their surfaces: alpha-D-mannose, N-acetyl-D-glucosamine, D-galactose, alpha-D-glucose, and alpha-L-fucose. AmNat 1.2 treated with Con A, WGA, and GPA only had the first 2 sugars named above and alpha-D-glucose residues. The results of the ID63 assay indicated AmNats 1.1 and 2.1 to be significantly more infective for mice than AmNats 1.2 and 3.1. The lectin analysis revealed that the 2, more infective, cloned VATs incubated with Con A or WGA emitted significantly (approximately 39% to approximately 62%) more fluorescence than the less infective ones. Thus there were significantly more numerous Con A and WGA binding sites on the more infective AmNats. The situation was reversed with regard to GPA. Upon treatment with this lectin, fluorescence emitted by AmNats 1.1 and 2.1 was significantly (approximately 56% to approximately 81%) lower than that recorded for the less infective AmNats 1.2 and 3.1. In light of our results, infectivity of T. congolense cloned VATs was correlated with the presence of higher numbers of alpha-D-mannose and N-acetyl-D-glucosamine residues and of lower numbers of alpha-D-glucose residues on the surface of the bloodstream trypanosomes. There appeared to be no correlation between infectivity and the numbers of D-galactose and alpha-L-fucose residues present on these parasites.

Animals↗
PubMed1978

Impairment of dolichyl saccharide synthesis and dolichol-mediated glycoprotein assembly in the aortic smooth muscle cell in culture by inhibitors of cholesterol biosynthesis.

25-Hydroxycholesterol treatment of the aortic smooth muscle cell inhibited the incorporation of acetate but not mevalonate into dolichol and cholesterol by 91 and 82%, respectively, and diminished the synthesis from glucose of cholesterol, dolichylpyrophosphoryl oligosaccharide, and dolichol-dependent glycoproteins. The dolichol-bound oligosaccharide unit contained approximately 10 Man/2 Glc/2 GlcNAc residues and appeared to be a precursor to protein-bound saccharide units which contained on the average 8 Man/1 Glc/2 GlcNAc residues. Mevalonate was found to protect the cells against the effect 25-hydroxycholesterol and to restore normal cellular synthesis of dolichyl saccharides and glycoproteins. It is suggested that hydroxymethylglutaryl coenzyme A reductase may function as a rate-controlling enzyme in the biosynthesis of not only sterols but also dolichols, and may as a result regulate the assembly of certain cellular glycoproteins.

Acetates↗
PubMed1994

Sialylation of terminal saccharides of glycoconjugates expressed by murine molar tooth germs developing in vitro and in vivo.

During development of the mammalian tooth germ the pattern of terminal saccharides of glycoconjugates changes, with many structures losing lectin reactivity in a consistent pattern. This study investigated whether the epitopes are lost or become masked by terminal sialylation, using a combination of neuraminidase treatment of sections and sialic acid-reactive lectins. The results suggested that most of the terminal galactosamine and fucose sites in the epithelial enamel organ were removed during morphogenesis. Conversely, during condensation of the dental mesenchyme, masked peanut agglutinin (PNA)-reactive galactose epitopes appeared. During differentiation and organisation of the mesenchyme into odontoblasts and a subodontoblastic layer the PNA-reactive sites became masked again. These regions also specifically expressed sialylated glucosamine. However, at the proliferating epithelial cervical loop galactose sites appeared to be masked. This was more pronounced during in vitro development when abnormal expression of PNA-reactive sites was found at the cervical loop. Additionally, fucosylated sites persisted in the enamel organ, further indicating that the expression of terminal saccharides was disrupted during development in the organ culture system. These data suggest that loss of terminal galactose and galactosamine is related to differentiation of the cells. However, whether this loss occurs by removal or sialic acid masking is not dependent either on the origin of the cells or the epitope being lost.

Animals↗
PubMed1977

Evidence for the participation of saccharide-lipids in the synthesis of the oligosaccharide chain of ovalbumin.

To obtain information on the mechanism of glycosylation of ovalbumin, three types of experiments were performed with either hen oviduct membrane preparations or tissue slices and the antibiotic tunicamycin. First, experiments involving the addition of tunicamycin to oviduct membranes demonstrated that this antibiotic inhibited the synthesis of a N-acetylglucosaminyl-lipid with the properties of N-acetyl-glucosaminylpyrophosphorylpolyisoprenol. No inhibitory effects on the other steps in the synthesis of oligosaccharide-lipid were observed. Thus, tunicamycin inhibits the lipid-linked pathway for membrane protein glycosylation by blocking the first step in the synthesis of oligosaccharide-lipid, namely, the synthesis of N-acetylglucosaminylpyrophosphorylpolyisoprenol. Second, in experiments using membranes prepared from oviduct tissue slices preincubated with tunicamycin, it was found that mannosylphosphoryldolichol was the only saccharide-lipid synthesized. This result indicates that tunicamycin administered in vivo depletes endogenous pools of N-acetylglucosamine-lipid precursors to oligosaccharide-lipid in a manner consistent with its activity in vitro. Finally, it was found that tissue slices incubated in the presence of tunicamycin synthesized the polypeptide chain of ovalbumin at almost normal rates. However, the protein newly synthesized in vivo did not contain labeled N-acetylglucosamine or mannose and had the properties of unglycosylated ovalbumin. These results indicate that saccharide-lipids participate in the assembly of the core oligosaccharide of the secretory glycoprotein, ovalbumin.

Acetylglucosaminidase↗
PubMed1996

Poly-N-acetyllactosaminyl saccharide chains of band 3 as determinants for anti-band 3 autoantibody binding to senescent and oxidized erythrocytes.

Natural IgG antibodies to band 3 glycoprotein of erythrocyte membrane (anti-band 3 IgG) are known to bind to senescent erythrocytes, and believed to initiate antibody-dependent phagocytic removal of the senescent cells from blood circulation. Anti-band 3 antibodies also bind to the erythrocytes with hereditary hemoglobin abnormalities such as sickle, beta-thalassemic and hemoglobin Köln erythrocytes. Oxidative stress appears to be responsible for the generation of senescent cell antigen on erythrocytes, to which anti-band 3 antibodies bind, since erythrocytes oxidized in vitro bind anti-band 3 IgG, and various oxidative modifications are observed in senescent erythrocytes as well as the erythrocytes with abnormal hemoglobin. Major antigenic sites of band 3 for anti-band 3 IgG autoantibodies are its sialylated poly-N-acetyllactosaminyl saccharide chains. The poly-N-acetyllactosaminyl saccharide chains on senescent erythrocytes are indeed involved in the antigenic sites on senescent erythrocytes. The finding of the carbohydrate epitopes and possible involvement of oxidative mechanism are compatible with the band 3 clustering hypothesis, in which clustering of band 3 molecules in erythrocyte membrane is supposed to be responsible for effective binding of anti-band 3 IgG to the cell surface, because the carbohydrate epitopes of band 3 can form multivalent epitopes on cell surface when band 3 molecules cluster, and oxidative stress can induce such clusters. Interestingly, poly-N-acetyllactosaminyl chains of band 3 on oxidized erythrocytes are also recognized by macrophages directly. Thus, poly-N-acetyllactosaminyl chains may play dual roles as determinants for recognition by anti-band 3 IgG and by macrophages.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1976

Lipid-saccharide intermediates in glycoprotein biosynthesis. II. Studies on the structure of an oligosaccharide-lipid from thyroid.

Structural studies have been performed on an oligosaccharide-lipid from thyroid believed to be an intermediate in glycoprotein synthesis. For these investigations the compound was isolated from the gland in unlabeled form as well as differentially radiolabeled in its saccharide, lipid, and phosphate portions by incubation of slices with [14C]- or [3H]glucose, [3H]mevalonic acid and [32P]phosphate, respectively. The unlabeled oligosaccharide-lipid was obtained in a chloroform/methanol/water (10/10/3) extract in a yield of about 1 nmol/g of thyroid and was purified therefrom by DEAE-cellulose chromatography. The saccharide moiety released from the glycolipid by mild acid hydrolysis was isolated by gel filtration and contained 11 mannose, 1 to 2 glucose, and 2 N-acetylglucosamine residues. The reducing terminal position of the oligosaccharide was occupied by 1 of the glucosamine residues and from these analyses a molecular weight of 2,415 was calculated. That glucose is an integral part of the molecule was further demonstrated by the finding that during Dowex 50 chromatography it remained as a constituent of the positively charged oligosaccharide produced by deacetylation with alkaline borohydride at 80 degrees. The phosphorus content of the purified unlabeled oligosaccharide-lipid was determined to be 2 residues per molecule, suggesting the presence of a pyrophosphate bridge between its carbohydrate and lipid portions. Further evidence for such a linkage region was provided by characterization of the products from mild acid and alkaline hydrolysis of the differentially radiolabeled glycolipid. These included dolichyl mono- and pyrophosphate, oligosaccharide phosphate, and free oligosaccharide. Digestion with alpha-mannosidase of the radiolabeled glycolipid led to the release of 39% of its mannose while from the free oligosaccharide 53% of this sugar was removed. Acetolysis of the [14C]oligosaccharide yielded a mannobiose and mannotriose as well as larger fragments consisting of mannose, glucose, and glucosamine. Smith periodate degradation gave rise to a small core segment (6 glycose residues) made up only of mannose and glucosamine from which half of the mannose residues could be released by alpha-mannosidase digestion. From these studies a tentative structure for the carbohydrate moiety of the oligosaccharide-lipid has been proposed. In this formulation an inner core (periodate-resistant) made up of 4 mannose and 2 N-acetylglucosamine residues is attached to the pyrophosphate group by the most internal glucosamine. This core, as well as an additional mannose and 1 to 2 glucose residues, constitutes the alpha-mannosidase-resistant fragment. More peripherally are found other mannose residues, all in alpha-linkage. In this structural scheme the glucose is located so as to prevent the enzymatic release of more internally situated alpha-linked mannose residues.

Acetylglucosamine↗
PubMed1984

Altered muscle saccharide pattern in X-linked muscular dystrophy.

Five lectins were used as fluorescence microscopic markers for sugar residues in skeletal muscle. Biopsy specimens were taken from patients with X-linked muscular dystrophy (Duchenne's and Becker's), patients with other neuromuscular diseases, and normal controls. In both the controls and the pathologic samples, concanavalin A gave a bright fluorescence of the myofiber surface, whereas soybean agglutinin and Dolichos biflorus agglutinin fluorescence was negative. Peanut agglutinin and wheat germ agglutinin were more avidly bound to the sarcolemma and/or endomysial connective tissue in the patients with X-linked muscular dystrophy than in the controls or the patients with other conditions. The altered saccharide pattern may reflect either a myofiber membrane change or a specific mesenchymal reaction in the dystrophic muscle.

Adolescent↗
PubMed1998

Saccharide-RNA recognition.

Among saccharides, the antibiotics of the aminoglycoside family are the best-studied class of molecules interacting with RNA. By binding to RNA targets, aminoglycosides act as inhibitors of protein biosynthesis, they interfere with protein-RNA interaction of retroviral regulatory elements, and they inhibit the catalytic action of ribozymes. Here, we survey the available data on molecular structural details of aminoglycoside-RNA interaction.

Aminoglycosides↗
PubMed1980

The structure of the m/z 101 ion in the spectra of permethylated saccharides.

In this paper the structure of the most important fragment ion ([C5H9O2]+, m/z 101) in the spectra of permethylated saccharides is investigated. The participation of the C-1 carbon atom in the formation of this ion has been quantitatively determined from the spectra of 13C labelled permethylated glucofuranosides. Investigation of the metastable ion and collisional activation spectra of m/z 101 yielded evidence for an acylic ion structure.

Chemical Phenomena↗
PubMed1997

The mast cell function-associated antigen exhibits saccharide binding capacity.

The mast cell function-associated antigen (MAFA) is a membrane glycoprotein first identified on rat mucosal type mast cells (line RBL-2H3) and known to inhibit the Fc epsilon RI-mediated secretory response. In its extracellular domain, an amino acid stretch homologous to the carbohydrate binding domain of calcium-dependent animal lectins has been found. To investigate its carbohydrate binding capacity, the MAFA has been expressed in the Spodoptera frugiperda insect cell line (Sf9) using the baculovirus expression system. Analysis by flow cytometry and surface labeling with 125I showed that the recombinant MAFA (rMAFA) was expressed as a monomeric and disulfide-linked homodimeric glycoprotein in the membrane of the insect cells, and both forms exhibited the same epitopes as the protein isolated from RBL-2H3 cells. Immunoaffinity-purified rMAFA was then employed for studies of its saccharide binding capacity by using different neoglycans and glycoproteins. The rMAFA was found to bind specifically terminal mannose residues in a Ca(2+)-dependent manner. These results support the notion that the extracellular domain of the MAFA is indeed able to bind ligands, which may be modulatory for the mast cell response.

Animals↗
PubMed1991

Polyacrylamide gel electrophoresis of reducing saccharides labeled with the fluorophore 8-aminonaphthalene-1,3,6-trisulphonic acid: application to the enzymological structural analysis of oligosaccharides.

Mono- and oligosaccharides, each containing a reducing end group, were labeled with the charged fluorophore 8-aminonaphthalene-1,3,6-trisulphonic acid and the resulting derivatives were separated with high resolution by polyacrylamide gel electrophoresis using a method developed recently (P. Jackson, Biochem. J. 1990, 270, 705-713) but with an alternative electrophoretic buffer system. The fluorescent derivatives of glucose and all its straight chain, alpha 1-4 linked, oligomers from maltose to maltoheptaose were well resolved. Various isomers such as maltose and lactose could be separated, as were maltose and cellobiose and some epimers, for instance glucose and galactose. The method was applied to the analysis of the partial sequential degradation of a complex oligosaccharide with neuraminidase and beta-galactosidase. Gels showing fluorescent saccharide band patterns were recorded in picomolar quantities either photographically or using an imaging system based on a cooled charge-coupled device.

Electrophoresis, Polyacrylamide Gel↗
PubMed1992

Human serum amyloid P is a multispecific adhesive protein whose ligands include 6-phosphorylated mannose and the 3-sulphated saccharides galactose, N-acetylgalactosamine and glucuronic acid.

Carbohydrate recognition by amyloid P component from human serum has been investigated by binding experiments using several glycosaminoglycans, polysaccharides and a series of structurally defined neoglycolipids and natural glycolipids. Two novel classes of carbohydrate ligands have been identified. The first is 6-phosphorylated mannose as found on lysosomal hydrolases, and the second is the 3-sulphated saccharides galactose, N-acetyl-galactosamine and glucuronic acid as found on sulphatide and other acidic glycolipids that occur in neural or kidney tissues or on subpopulations of lymphocytes. Binding to mannose-6-phosphate containing molecules and inhibition of binding by free mannose-6-phosphate and fructose-1-phosphate are features shared with mannose-6-phosphate receptors involved in trafficking of lysosomal enzymes. However, only amyloid P binding is inhibited by galactose-6-phosphate, mannose-1-phosphate and glucose-6-phosphate. These findings strengthen the possibility that amyloid P protein has a central role in amyloidogenic processes: first in formation of focal concentrations of lysosomal enzymes including proteases that generate fibril-forming peptides from amyloidogenic proteins, and second in formation of multicomponent complexes that include sulphoglycolipids as well as glycosaminoglycans. The evidence that binding to all of the acidic ligands involves the same polypeptide domain on amyloid P protein, and inhibition data using diffusible, phosphorylated monosaccharides, is potentially important leads to novel drug designs aimed at preventing or even reversing amyloid deposition processes without interference with essential lysosomal trafficking pathways.

Acetylgalactosamine↗
PubMed2004

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nuclear magnetic resonance analyses of end-functionalized saccharidic polymers: an example of a useful analytical technique combination.

The living cationic polymerization of a saccharidic monomer (1,2:3,4-di-O-isopropylidene-6-O-(2-vinyloxyethyl)-D-galactopyranose, GVE) gives rise to aldehyde end-capped polymers (PGVE--CHO) of low molar masses (<10 000 Da) and low molar mass distribution (<1.2). These polymers were derivatized by selective introduction of either hexamethylenediamine (PGVE-NH2) or 9-fluorenylmethyl carbazate (PGVE-Fmoc) end groups. The resulting polymers were fully characterized by complementary use of nuclear magnetic resonance (1H NMR) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The expected structure according to the polymerization mechanism, the occurrence of side reactions and the success of the post-functionalization reactions were confirmed.

Chemistry Techniques, Analytical↗
PubMed2002

Analysis of saccharides in beer samples by flow injection with electrospray mass spectrometry.

Saccharides in foods play important roles, as they are essential substrates for fermentation processes. In brewing, the concentration of maltooligosaccharides influences the characteristics of beers and therefore their determination is of great practical interest. Electrospray ionization mass spectrometry (ESI-MS) was applied to identify and characterise maltooligosaccharides in beer samples. The effects due to different cation concentrations and dilution of samples were studied. Furthermore, quantitative analyses of maltooligosaccharides by means of flow-injection ESI-MS (FI/ESI-MS) of 1-microL beer samples (diluted 1000-fold) are described.

Beer↗
PubMed1993

Reduction of ricin toxicity without impairing the saccharide-binding properties by chemical modification of the carboxyl groups.

The usefulness of ricin as a research tool is handicapped by its extremely biohazardous nature. In this work, ricin toxicity has been reduced by chemical modification of carboxyl groups using 1-ethyl-3(3-dimethylaminopropyl) carbodiimide and [14C]glycine methyl ester. The reaction was carried out in 8 M urea and in the presence of 0.1 M lactose to protect the groups involved in saccharide binding. Together with carboxyl groups, tyrosine residues were also modified. The maximum modification achieved was 13 carboxyl groups and 7 tyrosines per molecule (about 30% of total carboxyls and tyrosines). The modification did not alter substantially the strength and specificity of the carbohydrate-binding ability of the lectin, as observed by hemagglutination tests and by inhibition assays with different carbohydrate structures. However, the LD50 decreased 90-fold when the highest modification was achieved. Therefore, the modified lectin can be used more safely in the study of galactose-containing carbohydrates.

Animals↗
PubMed1998

Immobilization of saccharides and peptides on 96-well microtiter plates coated with methyl vinyl ether-maleic anhydride copolymer.

We have previously reported a method to immobilize protein ligands on microtiter plates coated with methyl vinyl ether-maleic anhydride copolymer (MMAC) [Isosaki, K., et al. (1992) J. Chromatogr. 597, 123-128]. In this study, we improved the MMAC method to efficiently immobilize not only small ligands such as peptides and oligosaccharides, which could not be efficiently immobilized previously, but also heparin via its reducing end. Amino and hydrazino groups were introduced to MMAC-coated microtiter plate wells by coupling to acid anhydride groups of MMAC with 1,6-hexamethylenediamine and adipic acid dihydrazide, respectively. The amino groups introduced were allowed to react with peptides by use of divalent cross-linkers. Hydrazino groups were allowed to react with formyl groups of saccharides by reductive amination. Peptides and oligosaccharides were immobilized in a dose-dependent manner by these methods. In the case of the angiotensin peptide thus immobilized, the detection limit by monoclonal antibodies was as low as 0.1-1 fmol peptide per well. Application of 20-200 nmol oligosaccharides to the well was sufficient to immobilize and subsequently detect lectins. Furthermore, heparin immobilized on the hydrazinocoated wells was successfully used for the binding assay of annexin IV.

Adipates↗
PubMed1996

One electron reduction of vanadate(V) to oxovanadium(IV) by low-molecular-weight biocomponents like saccharides and ascorbic acid: effect of oxovanadium(IV) complexes on pUC18 DNA and on lipid peroxidation in isolated rat hepatocytes.

One electron reduction of vanadate(V) to vanadyl(IV) occurs in the presence of biocomponents, such as, saccharide s and L-ascorbic acid under physiological conditions. The vanadyl(IV) complexes thus generated have been demonstrated to introduce nicks in pUC18 DNA in the absence or in the presence of hydrogen peroxide and also exhibit lipid peroxidation in isolated rat hepatocytes. Thus the reducing and complexing abilities of these molecules may help in understanding the in vivo reduction and the resultant toxicity to cells incubated with vanadate(V).

Animals↗