Showing papers on "Sialic acid published in 1974"

The histochemical demonstration of o-acylated sialic acid in gastrointestinal mucins their association with the potassium hydroxide-periodic acid-schiff effect

Abstract: O-Acylated sialic acids have been demonstrated histochemically in the epithelial mucins of the lower end of the gastrointestinal tract. The potassium hydroxide-periodic acid-Schiff effect has been ...

Alterations of Membrane Glycopeptides in Human Colonic Adenocarcinoma

Abstract: Membrane glycopeptides were examined in human colonic adenocarcinoma and normal colonic mucosa. The carbohydrates of membrane glycopeptides were found to be markedly reduced in tumor tissue and the relative proportions of the various sugars were altered. Although all of the sugars were lower in tumor tissue when compared to the adjacent normal mucosa, galactosamine, fucose, and sialic acid were more significantly reduced. Examination of the blood group activity and lectin-binding properties of membrane glycopeptides revealed that specific carbohydrate structures had changed in the tumor tissue. Most striking of these changes was the disappearance of glycoprotein-associated blood group A activity. Assay of the enzyme responsible for synthesis of the blood group A determinant showed that this glycosyltransferase activity was greatly diminished in tumor tissue. A galactosyltransferase and a fucosyltransferase were also significantly lower in the tumor tissue whereas the levels of another galactosyltransferase and a sialyltransferase were unaltered. Glycosidase activities in the normal and tumor tissues were similar. The results show that an alteration in glycoprotein biosynthesis occurred during tumorigenesis that resulted in a modified membrane glycoprotein composition and that these changes are probably a reflection of reduced levels of the enzymes responsible for glycoprotein synthesis.

Glycoproteins of Sindbis Virus: Preliminary Characterization of the Oligosaccharides

Abstract: The carbohydrate content of Sindbis virus was determined by gas chromatographic analysis. The two viral glycoproteins were found to be approximately 8% carbohydrate by weight. Mannose is the sugar present in the largest amount. Smaller amounts of glucosamine, galactose, sialic acid, and fucose were also detected. Each of the two viral glycoproteins appears to contain two structurally unrelated oligosaccharides. Two of the three Sindbis-specific glycoproteins found in infected chick cells were shown to contain short, unfinished oligosaccharides.

Use of mass spectrometry for the carbohydrate composition and sequence analysis of glycosphingolipids.

Abstract: Mass spectrometry has been applied for a detailed structural characterization of glycosphingolipids. Methylated and methylated plus reduced glycolipids (amide groups of ceramide and amino sugars were reduced to the corresponding amines) were found the most useful derivatives. Molecular weight ions [M – 1] were not obtained for methylated lipids with more than four sugar units, but were easily obtained for reduced derivatives, so far with six sugars. Spectra of reduced derivatives showed very abundant ions containing the complete carbohydrate and the fatty acid, allowing a conclusion to be made concerning the carbohydrate composition (ratio of hexose and hexosamine and sialic acid). In addition, conclusive information was obtained for the carbohydrate sequence, including branching of the chain. By a combined use of both derivatives the long chain base and fatty acid composition was also evident. Spectra are discussed for a synthetic monoglycosylceramide, the Forssman glycolipid hapten (pentaglycosylceramide) and two gangliosides (a triglycosylceramide and a pentaglycosylceramide). The mass spectrum of the Forssman glycolipid provides the first conclusive evidence for two amino sugars in the terminal disaccharide of the molecule.

New Sialic Acids

Abstract: 1 Sialic acids were released by dilute acids or by neuraminidase from glycoproteins of bovine and equine submandibular glands, from glycoproteins of equine blood plasma and from equine erythrocyte membranes. They were purified by ion-exchange chromatography and fractionated on cellulose. 2 The following methods have been adapted to the structural analysis of sialic acids with regard to the nature and position of the N-acyl and O-acyl groups. a) Thin-layer chromatography in two dimensions with intermediate ammonia treatment to remove the O-acyl groups leading to the identification of the basic N-acylneuraminic acids. b) Thin-layer chromatography in two dimensions with intermediate hydroxylamine treatment allowing the identification of the O-acyl groups of sialic acids as hydroxamates. c) Gas-liquid chromatography for identification of the different N-acylated and O-acylated sialic acids. 3 The structure of the following new sialic acids have been established: a) N-glycoloyl-8-O-acetylneuraminic acid isolated from glycoproteins of bovine submandibular glands; b) N-acetyl-4-O-glycoloylneuraminic acid isolated from glycoproteins of equine submandibular glands and also occurring in equine blood plasma and equine erythrocyte membranes; c) N-acetyl-7 or 8-O-glycoloylneuraminic acid detected in glycoproteins from bovine submandibular glands. 4 The O-acetylated N-glycoloylneuraminic acid first detected in horse erythrocyte membranes by Hakomori and Saito and in horse serum by Pepper, was determined to be N-glycoloyl-4-O-acetyl-neuraminic acid; it was also found to occur in submandibular glands of horse. 5 The sialic acid patterns from the different biological materials investigated are compared.

Changes in composition of mucin in the mucosa adjacent to carcinoma of the colon as compared with the normal: a biochemical investigation.

Abstract: Fifteen surgical specimens from patients with carcinoma of the colon and rectum were studied. Scrapings from normal mucosa distant from the tumour and from macroscopically normal mucosa adjacent to the tumour (;transitional') were used for chemical estimation of hexosamines, sialic acid, and proteins. The presence of hexosamines and sialic acid was confirmed in both normal and transitional mucosa. Transitional mucosa showed increased levels of total hexosamines and sialic acid as compared with the normal and this was accompanied by an increase in neuraminidase-sensitive sialic acids. The present data have been compared with previous histochemical and autoradiographic studies and it is suggested that the changes described in the transitional mucosa are transformations representing an early stage of carcinogenesis.

A study on the mechanism of intercellular adhesion. Effects of neuraminidase, calcium, and trypsin on the aggregation of suspended HeLa cells.

Abstract: Aggregation of suspended HeLa cells is increased on removal of cell surface sialic acid. Calcium ions promote aggregation whereas magnesium ions have no effect. The calcium effect is abolished by previous treatment of the cells with neuraminidase. Trypsinization of the HeLa cells followed by thorough washing diminishes the rate of mutual cell aggregation. Subsequent incubation with neuraminidase restores the aggregation rate to the original value before trypsin treatment. Cells which had acquired a greater tendency for aggregation after removal of peripheral sialic acid lose this property when subsequently treated with trypsin. Calcium ions have no aggregative effect on trypsinized cells. In contrast to HeLa cells, aggregation of human erythrocytes was not increased after treatment with neuraminidase or on addition of calcium. The results with HeLa cells are interpreted as follows: (a) Trypsin-releasable material confers adhesiveness upon the cells. (b) The adhesive property of this material is counteracted by the presence of cell surface sialic acids. (c) Calcium ions exert their effect by attenuating the adverse effect of sialic acid.

Undialyzable growth factors for Lactobacillus bifidus var. pennsylvanicus. Protective effect of sialic acid bound to glycoproteins and oligosaccharides against bacterial degradation.

Abstract: Lactobacillus bifidus var. pennsylvanicus requires human milk constituents for growth. All growth factors so far known represent low-molecular derivatives of d-glucosamine (2-amino-2-deoxy-d-glucose). Some higher-molecular undialyzable sialic acid-containing oligosaccharides from human milk and some sialo-glycoproteins from different body fluids have been tested for growth promoting activity. Isolation, purification and some structural properties of the oligosaccharides are described. Without pretreatment by neuraminidase, none of the substances exhibit any growth promoting activity. After incubation with neuraminidase from Vibrio cholerae, the activity of the oligosaccharides increased in close correlation to the content of N-acetyl-d-glucosamine to the same extend as ethyl-2-acetamido-2-deoxy-β-d-glucopyranoside, the most active derivative of N-acetyl-d-glucosamine known. The activity of α1-acid glycoprotein from human serum, urinary glycoprotein and submaxillary mucin was considerably lower, possibly due to the different linkages of sialic acid and their more complex structures. The possible protective effect of sialic acid bound to oligosaccharides and glycoproteins against degradation by bacterial enzymes is discussed.

Isolation and characterisation of glycoproteins from sputum.

Abstract: Sputum has been separated into a sol and a gel phase by ultracentrifugation and the components of these phases examined. A glycoprotein of high molecular weight as well as serum albumin, immunoglobulin A, α1 acid glycoprotein and lactoferrin were detected in the sol phase by gel filtration and immunodiffusion studies. A glycoprotein of similar chemical composition was isolated from the gel phase by solubilisation in 6 M urea/0.1 M NaCl followed by fractional precipitation with ethanol. The carbohydrate content of this glycoprotein, termed the bronchial glycoprotein, varied from 58% (w/w) to 69% (w/w) with sputum from different patients and was composed of fucose, galactose, galactosamine, glucosamine and N-acetylneuraminic acid. Serine, threonine and proline constituted 44% (w/w) of the amino acid residues of the bronchial glycoprotein and an alkaline borohydride cleavage study indicated that O-glycosidic linkages exist between N-acetylgalactosamine and the hydroxyamino acids in the peptide core. Fractionation of the bronchial glycoprotein on DEAE-Sephadex A-25 yielded fractions enriched in sulphate and sialic acid but separate fuco, sialo and sulpho glycoproteins were not obtained. Similarly fractionation of the oligosaccharides released by the action of alkaline borohydride yielded a complex mixture of oligosaccharides but sulphated oligosaccharides free of sialic acid were not obtained. Separation of the oligosaccharides into two fractions of different sizes showed that sulphate content was greatest in the larger oligosaccharides whereas sialic acid content was highest in the smaller oligosaccharides. A methylation study of the bronchial glycoprotein, neuraminidase-digested bronchial glycoprotein and mild acid-hydrolysed bronchial glycoprotein revealed that the N-acetylneuraminic acid was linked to C-3 of penultimate galactose units. Fucose occurs in three different linkages, approximately 50% is linked to C-2 of penultimate galactose units, approximately 25% is linked to C-4 of glucosamine residues already substituted at C-3 and the remainder is linked to C-3 of glucosamine residues already substituted at C-4.

Angiotensin-Converting Enzyme from Rabbit Pulmonary Particles

Abstract: Angiotensin-converting enzyme has been solubilized from rabbit pulmonary particles and purified to homogeneity. The molecular weight of the native enzyme was estimated to be about 136,000 by glycerol gradient centrifugation, and a value of 140,000 was obtained for the reduced denatured protein by disc-gel electrophoresis in the presence of sodium dodecyl sulfate and 2-mercaptoethanol. The enzyme was found to be a glycoprotein with carbohydrate accounting for approximately 16% of its dry weight. The major sugar residues were identified as galactose, N-acetylglucosamine, and mannose, with smaller amounts of fucose and sialic acid. The homogeneous enzyme catalyzed the release of His-Leu from the COOH-terminus of angiotensin I and of Phe-Arg and Ser-Pro from that of bradykinin.

Isolation and Characterization of Oligosaccharides from Canine Submaxillary Mucin

Abstract: Pure mucin isolated from canine submaxillary glands was treated with alkaline borohydride and products of degradation were fractionated by a procedure that included ion-exchange chromatography, gel filtration, high-voltage electrophoresis and paper chromatography. Seven acidic, reduced oligosaccharides were isolated being divided into two distinct types: one, containing sialic acid and no glucosamine or sulfate (type A) and the other containing glucosamine and sulfate but no sialic acid (type B). The most complete oligosaccharide of type A designated component (I) was a tetrasaccharide α-l-fucopyranosyl-(1 2)-d-galactopyranosyl-[N-acetylneuraminyl-(2 6)]-2-acetamido-2-deoxy-d-galactitol. The most complex oligosaccharide of type B designated component (V) has a hexasaccharide with the following structure: α-l-fucopyranosyl-(1 2)-β-d-galactopyranosyl-(1 3, 4, or 6)-β-2-acetamido-2-deoxy-d-glucopyranosyl 3 or 4 sulfate-(1 6)-α-l-fucopyranosyl-(1 2)]-β-d-galactopyranosyl-(1 3) 2-acetamido-2-deoxy-d-galactitol. All the other acidic isolated oligosaccharides were derived from these two main components. No oligosaccharide containing both sialic acid and glucosamine sulfate could be demonstrated. Based on these structural features, a possible biosynthetic pathway leading to the two different oligosaccharide chains is discussed. Variations in ratios of sugars observed in canine submaxillary mucin and especially the reciprocal relationship between sialic acid and fucose noted earlier (1962) by Dische, Pallavicini, Kavasaki, Smirnow, Cizek and Chien may reflect variations in the proportions of these two types of oligosaccharides.

The Effect of Enzymes on Structural and Biological Properties of Semliki Forest Virus

Abstract: Summary Treatment of purified Semliki Forest virus with neuraminidase released sialic acid, raised the isoelectric point of the virus by 0.35 pH units but had no effect on the infectivity, haemagglutinating (HA) activity or surface antigenic properties and did not alter the electrophoretic mobility of the envelope glycoproteins on polyacrylamide gels. Treatment of virus with a mixture of sugar hydrolases lowered infectivity and HA activity and slightly increased the electrophoretic mobility of the envelope glycoproteins, but had no measurable effect on surface antigenic properties. Treatment with bromelain digested the envelope glycoproteins, destroyed infectivity, HA activity and surface antigenicity and yielded a sub-viral particle containing lipid. Treatment of this particle with phospholipase C produced a core particle indistinguishable by sedimentation analysis from the nucleocapsids found in infected cells.

A membrane receptor protein for asialoglycoproteins.

Abstract: Publisher Summary Specific receptor sites have been identified on hepatic plasma membranes that appear to be involved in the catabolism of plasma glycoproteins by virtue of their ability to bind selectively to asialoglycoprotein, i.e., glycoproteins from which the terminal sialic acid residues have been removed. These receptors have been solubilized from particulate liver preparations by extraction with the nonionic detergent Triton X-1003 and further purified by affinity chromatography on a column of Sepharose to which asialo-orosomucoid has been covalently attached. Binding of the receptor protein to the immobilized ligand occurs at a neutral or slightly alkaline pH and has an absolute requirement for calcium; elution is accomplished either by reducing the pH to between 5.6 and 6.4 or by addition of the calcium chelator EDTA. Excess Triton X-100 can be readily removed, prior to elution of the receptor by washing the column with a neutral, calcium-containing, aqueous buffer.