The structure of the O-glycosylically-linked oligosaccharide chains of LPG-I,a glycoprotein present in articular lubricating fraction of bovine synovial fluid

Periodate oxidation of LPG-1 established that N-acetylneuraminic acid residues are linked preponderantly α-(2→3) to D-galactose residues. The resistance of 2-acetamido-2-deoxyD-galactose residues to periodate oxidation suggests that they are linked at either O-3 or O-4 to D-galactose residues. After treatment of LPG-I with alkaline sulfite, ≈80% of 2-acetamido-2-deoxygalactose was recovered as the sulfonic acid derivative. The Gal→GalNAc disaccharide released from sialic-acid-free LPG-I by digestion with endo-2-acetamido-2-deoxy-α-D-galactosidase (which suggests an α-D-GalNAc→-L-Ser or -L-Thr linkage) gave a high color-yield in the Morgan—Elson reaction, indicating that 2-acetamido-2-deoxy-D-galactose residues are linked at C-3 to D-galactose residues. The migration of the released Gal-GalNAc disaccharide was the same as that of a standard sample of O-β-D-galactosyl-(1→3)-2-acetamido-2-deoxy-D-galactose. Treatment of sialic acid-free LPG-I with Streptococcus pneumoniae β-D-galactosidase, which hydrolyzes only galactosides linked β-D-(1→4) gave no free D-galactose, whereas treatment of LPG-I with bovine testes β-D-galactosidase released > 90% of D-galactose. These results provide evidence for β-D-Galp-(1→3)-α-D-GalNAcp-(1→3)-L-Ser or -L-Thr and α-NeuAc-(2→3)-β-D-Galp-(1→3)-α-D- GalNAcp-(1→3)-L-Ser or -L-Thr structures. The sensitivity of the methods used and the recovery of constituents following treatment of LPG-I do not rule out the occurrence of small amounts of other tri- or tetra-saccharide chains.     

Synthesis of 2-acetamido-2-deoxy-4-O-alpha-L-fucopyranosyl-alpha-D-glucopyranose]

Condensation of 2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl bromide with benzyl 2-acetamido-3,6-di-O-benzyl-alpha-D-glucopyranoside in dichloromethane-N,N-dimethylformamide, in the presence of tetraethylammonium bromide, diisopropylethylamine, and molecular sieve (halide ion-catalyzed reaction), gave benzyl 2-acetamido-3,6-di-O-benzyl-2 deoxy-4-O-(2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl)-alpha-D-glucopyranoside in crystalline form in 82% yield. Hydrogenolysis of the benzyl groups gave the title disaccharide, in crystalline form in 90% yield, which was characterized by a crystalline peracetylated alpha-D derivative.     

Modified assay-procedure for guanosine diphosphate-L-fucose: 2-acetamido-2-deoxy-beta-D-glucopyranoside-(1 leads to 4)-alpha-L-fucosyltransferase with the aid of synthetic phenyl 2-acetamido-2-deoxy-4-O-alpha-L-fucopyranosyl-3-O-beta-D-galactopy-ranosyl -beta-D-glucopyranoside as a reference compound

Starting from phenyl 2-acetamido-2-deoxy-4,6-O-(p-methoxybenzylidene)-beta-D-glucopyranoside (1), chemical syntheses were developed for phenyl 2-acetamido-2-deoxy-3-O-beta-D-galactopyranosyl-beta-D-glucopyranoside (4) and phenyl 2-acetamido-2-deoxy-4-O-alpha-L-fucopyranosyl-3-O-beta-D-galactopyranosyl -beta-D-glucopyranoside (8). Thin-layer chromatography in the solvent system 6:4:1:5 (v/v) 2-propanol-ethyl acetate-ammonium hydroxide-water clearly separated the synthetic trisaccharide 8 (RF 0.69) from synthetic disaccharide 4 (RF 0.78), fucose (RF 0.56), and GDP-fucose (which remained at the origin). Based upon this observation, a modified method for the determination of GDP-L-fucose: N-acetylglucosaminide-(1 leads to 4)-alpha-L-fucosyltransferase was developed that employed the synthetic disaccharide 4 as an acceptor, and compound 8 as an authentic reference-compound. This modified assay-procedure can simultaneously monitor possible competing reactions which may interfere with determination of alpha-(1 leads to 4)-L-fucosyltransferase activity; these include phosphorylase and alpha-L-fucosidase activities, and incorporation of alpha-L-[14C]-fucose into endogenous acceptors of enzyme preparations. Thus, the modified assay-procedure should facilitate determination of alpha-(1 leads to 4)-L-fucosyltransferase.     

Incompatible blood-group A determinants in tumoral mucins. Isolation of oligosaccharides having a 2-acetamido-2-deoxy-alpha-D-galactopyranosyl group at the non-reducing end

Two glycopeptide fractions were obtained from pseudomyxomatous mucins secreted by an ovarian cystadenocarcinoma from a female having blood-group B, and by an appendix tumor from a male having blood-group O. The carbohydrate and amino acid content of these fractions suggests the presence of numerous carbohydrate side-chains linked through O-glycosyl bonds to a peptide core rich in threonine and proline. The two glycopeptide fractions exhibit compatible B- and H-blood-group activities. They are reactive towards Dolichos biflorus lectin and human anti-A agglutinins, and so exhibit an incompatible A activity. Alkali-borohydride degradation of Pronase-digested glycopeptides gave dialyzable oligosaccharides that were purified and shown to possess 2-acetamido-2-deoxygalactitol at the terminal reducing-end. 2-Acetamido-2-deoxyglucose, galactose, fucose, and neuraminic acid were absent, or present, in variable proportions. Four oligosaccharides containing 2-acetamido-2-deoxy-D-galactose residues were reactive towards Dolichos biflorus lectin and human anti-A agglutinins, indicating the presence, at the nonreducing end, of a 2-acetamido-2-deoxy-alpha-D-galactopyranosyl group, responsible for blood-group A activity.     

A convenient synthon for the synthesis of the determinant oligosaccharides Le and ABH (type 1)

Precursors of blood group oligosaccharides ABH (type 1) and Le have been synthesized starting from benzyl 2-acetamido-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-6-O-ben zyl-2- deoxy-alpha-D-glucopyranoside after simple blocking and deblocking steps. The above disaccharide was prepared by regioselective galactosylation of benzyl 2-acetamido-6-O-benzyl-2-deoxy-alpha-D-glucopyranoside under Helferich conditions in 69% yield.     

Determination of the position of linkage of 2-acetamido-2deoxy-D-galactose and 2-acetamido-2-deoxy-D-glucose residues in oligosaccharides and glycoproteins. Synthesis of 2-acetamido-2deoxy-D-xylitol and 2-acetamido-2-deoxy-L-threitol

A method has been studied for the determination of the position of the linkage of the 2-acetamido-2-deoxy-D-galactose and 2-acetamido-2-deoxy-D-glucose residues in oligosaccharides and glycoproteins that is based on the borohydride reduction of the reducing terminal residues to the corresponding alditol derivatives periodate oxidation, borohydride reduction, hydrolysis (eventually followed by borohydride reduction), separation of the fragments as per-O-(trimethylsilyl) or per-O-(trifluoroacetyl) derivatives, and identification of the fragments as derivatives of 2-acetamido-2-deoxyglycerol, 2-acetamido-2-deoxy-L-threitol, 2-acetamido-2-deoxy-L-arabinitol, 2-acetamido-2-deoxy-D-xylitol, 2-acetamido-2-deoxy-D-galactitol, and 2-acetamido-2-deoxy-D-glucitol by gas-liquid chromatography-mass spectrometry. New syntheses for the standard compounds 2-acetamido-2-deoxy-L-threitol and 2-acetamido-2-deoxy-D-xylitol are described.     

The behavior of some aldoses with 2,2-dimethoxypropane-N,N-dimethylformamide-p-toluenesulfonic acid. I. At room temperature (25 degrees)

When treated at room temperature with a small excess of 2,2-dimethoxypropane in N,N-dimethylformamide solution in the presence of a trace of p-toluenesulfonic acid, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-mannose, 2-acetamido-2-deoxy-D-galactose, and D-glucose yield the corresponding 4,6-O-isopropylidenealdo-pyranoses. D-Mannose, however, gives the known 2,3:5,6-di-O-isopropylidene-D-mannofuranose.     

Structural characterization of the antigenic capsular polysaccharide and lipopolysaccharide O-chain produced by Actinobacillus pleuropneumoniae serotype 15.

The specific capsular polysaccharide produced by Actinobacillus pleuropneumoniae serotype 15 was determined to be a high-molecular-mass polymer having [alpha]D + 69 degrees (water) and composed of a linear backbone of phosphate diester linked disaccharide units of 2-acetamido-2-deoxy-D-glucose (D-GlcNAc) and 2-acetamido-2-deoxy-D-galactose (D-GalNAc) residues (1:1). Thirty percent of the D-GalNAc residues were substituted at O-4 by beta-D-galactopyranose (beta-D-Galp) residues. Through the application of chemical and NMR methods, the capsule, which defines the serotype specificity of the bacterium, was found to have the structure [structure: see text]. The O-polysaccharide (O-PS) component of the A. pleuro pneumoniae serotype 15 lipopolysaccharide (LPS) was characterized as a linear unbranched polymer of repeating pentasaccharide units composed of D-glucose (2 parts) and D-galactose (3 parts), shown to have the structure [structure: see text]. The O-PS was chemically identical with the O-antigen previously identified in the LPSs produced by A. pleuro pneumoniae serotypes 3 and 8.     

Preparation from keratin sulfate of substrates for the measurement of 2-acetamido-2-deoxy-D-glucose 6-sulfate sulfatase and (1 goes to 3)-N-acetyl-beta-D-glucosaminidase

An extract of bacterial cells Pseudomonas sp. IFO-13309 grown on medium containing 0.1% bovine cornea keratan sulfate of low sulfate content degraded exhaustively bovine cornea keratan sulfate to give 2-acetamido-2-deoxy-beta-D-gluco-pyranosyl 6-sulfate-(1 goes to 3)-D-galactose, isolated by gel filtration on Sephadex G-25 and purified by preparative paper chromatography. This was reduced with sodium borotritide to give 2-acetamido-2-deoxy-beta-D-glucopyranosyl 6-sulfate-(1 goes to 3)-D-[1-3H]galactitol, purified by gel filtration on Sephadex G-15, which was an excellent substrate for the measurement of 2-acetamido-2-deoxy-D-glucose 6-sulfate sulfatase. The reduced, radioactive monosulfated disaccharide was desulfated with methanolic 70mM hydrogen chloride and purified by gel filtration on Sephadex G-15 to give O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-(1 goes to 3)-D-[1-3H]galactitol, which allowed the measurement of (1 goes to 3)-N-acetyl-beta-D-glucosaminidase. This enzyme may participate in the normal degradation of keratan sulfate.     

Determination of 2-acetamido-2-deoxy-D-galactose and mechanism of formation of chromogens.

A method for the colorimetric determination of 2-acetamido-2-deoxy-D-galactose was developed. The procedure is based on the high reactivity of the aldehyde group of this amidosugar with pentane-2,4-dione in anhydrous alkaline conditions. The product of reaction was crystallized and the structure 1-C-acetonyl-2-acetamido-2-deoxy-D-galactitol was deduced from chemical evidence. When the N-acetyl group of this compound is split off by hydrolysis, the formation of pyrrole groups ensues by condensation of the free amino group with the carbonyl group of the chain at C-1. 2-Methylpyrrole was isolated by steam distillation after mild alkaline hydrolysis and estimated by reaction with p-dimethylaminobenzaldehyde. A more complex pyrrole is formed during acid hydrolysis under the conditions used in the direct Ehrlich reaction.     

Synthesis of 4-deoxy-4-fluoro analogues of 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-galactose and their effects on cellular glycosaminoglycan biosynthesis

4-Deoxy-4-fluoro analogues of 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-galactose were synthesized and evaluated as inhibitors of hepatic glycosaminoglycan biosynthesis. 2-Acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-4-fluoro-D-glucopyranose (16) exhibited a reduction of [3H]GlcN and [35S]SO4 incorporation into hepatocyte cellular glycosaminoglycans to 12 and 18%, respectively, of the control cells, at 1.0 mM. Similarly, 2-acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-4-fluoro-D-galactopyranose (31) exhibited a reduction of [3H]GlcN and [35S]SO4 incorporation to 1 and 9%, respectively, of the control cells, at 1.0 mM. Unlike 16, 31 exhibited a reduction of [14C]Leu incorporation into cellular protein to 57% of control cells, at 1.0 mM.     

Structure of a 2-aminoethyl phosphate-containing O-specific polysaccharide of Proteus penneri 8 from a new serogroup O67.

An acidic O-specific polysaccharide was obtained by mild acid degradation of the Proteus penneri 8 lipopolysaccharide and found to contain D-glucose, D-galacturonic acid, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-galactose, 2-acetamido-2,6-dideoxy-L-galactose (L-FucNAc) and 2-aminoethyl phosphate (PEtn) in the ratios 2 : 1 : 1 : 1 : 1 : 1. 1H and 13C NMR spectroscopy was applied to the intact and dephosphorylated polysaccharides, and the following structure of the hexasaccharide repeating unit was established: The O-specific polysaccharide has a unique structure, and, accordingly, we propose for P. penneri 8 a new Proteus O67 serogroup, in which this strain is at present the single representative. The nature of epitopes on LPS of P. penneri 34, P. mirabilis O16, P. mirabilis O23 and P. vulgaris O22, which cross-react with O-antiserum against P. penneri 8, is discussed.     

Structural studies on the specific type VII pneumococcal polysaccharide

The specific type VII pneumococcal polysaccharide was isolated from the crude capsular material by precipitative and chromatographic methods. It contained D-galactose, D-glucose, L-rhamnose, 2-acetamido-2-deoxy-D-glucose, and 2-acetamido-2-deoxy-D-galactose in the molar ratio of 3.5:2.3:3.0:2.1:1.0. Some of its structural features were revealed by methylation studies, time-lapse hydrolysis, periodate oxidation, and enzymic hydrolysis. The polysaccharide is branched at residues of D-galactose and 2-acetamido-2-deoxy-D-galactose. Non-reducing end groups consisted of D-galactopyranose and 2-acetamido-2-deoxy-D-glucopyranose residues, with the former predominating. Major components of the linear chains were (1→3)-linked L-rhamnose and (1→4)-linked D-glucose; the minor ones were (1→2)-linked L-rhamnose, (1→6)-linked D-galactose, and (1→6)-linked 2-acetamido-2-deoxy-D-glucopyranose. The (1→4)-linked D-glucose components may be present as cellobiose residues. The results are in accord with structural features deduced from the serological cross-reactivity of this polysaccharide.     

Transglycosylation Catalyzed by Almond β-glucosidase and Cloned Pichia etchellsii β-glucosidase II using Glycosylasparagine Mimetics as Novel Acceptors

The stability of almond β-glucosidase in five different organic media was evaluated. After 1 hour of incubation at 30°C, the enzyme retained 95, 91, 81, 74 and 56% relative activity in aqueous solutions [30% (v/v)] of dioxane, DMSO, DMF, acetone and acetonitrile, respectively. Transglucosylation involving p-nitrophenyl β-D-glucopyranoside as donor and β-1-N-acetamido-D-glucopyranose, which is a glycosylasparagine mimic, as acceptor was explored under different reaction conditions using almond βglucosidase and cloned Pichia etchellsii β-glucosidase II. The yield of disaccharides obtained in both reactions turned out to be 3%. Both enzymes catalyzed the formation of (1→3)- as well as (1→6)- regioisomeric disaccharides, the former being the major product in cloned β-glucosidase II reaction while the latter predominated in the almond enzyme catalyzed reaction. Use of β-1-N-acetamido-D-mannopyranose and β-1-N-acetamido-2-acetamido-2-deoxy-D-glucopyranose as acceptors in almond β-glucosidase catalyzed reactions, however, did not afford any disaccharide products revealing the high acceptor specificity of this enzyme.     

Carbohydrate-binding specificity of the so-called galactose-specific phytohemagglutinins.

The carbohydrate-binding specificities of various so-called galactose-specific phytohemagglutinins were investigated by means of hemagglutination-inhibition assays. As hapten inhibitors, glycopeptides prepared by pronase-digestion of various glycoproteins (porcine submaxillary mucin, bovine submaxillary mucin, and porcine thyroglobulin), and several glycosides of D-galactose and 2-acetamido-2-deoxy-D-galactose were employed. The results indicate that these galactose-specific phytohemagglutinins may recognize the sugar residue penultimate to D-galactose or 2-acetamido-2-deoxy-D-galactose residues of the sugar chain with which they interact, and that they can be classified into three groups based on the type of sugar sequence which they primarily recognize.     

Multigram syntheses of the disaccharide repeating units of chondroitin 4- and 6-sulfates.

The multigram syntheses of beta-D-glucopyranosyluronic acid-(1-->3)-2-acetamido-2-deoxy-4- and 6-O-sulfo-D-galactopyranose disodium salt, the disaccharide repeating units of chondroitin 4- and 6-sulfates, are described. The disaccharide benzyl methyl 2,3,4-tri-O-benzoyl-beta-D-glucopyranosyluronate- (1-->3)-2-acetamido-2-deoxy-alpha-D-galactopyranoside was used as a common intermediate. Selective benzoylation at O-6 followed by O-sulfonation at C-4 of the aminosugar moiety, saponification and catalytic hydrogenation afforded the 4-O-sulfo derivative, whereas selective O-sulfonation at C-6 followed by similar deprotection steps provided the 6-O-sulfo derivative in high yield.     

The synthesis ofP1-[2-acetamido-2-deoxy-3-O-(β-D-glucopyranosyluronic acid)-α-D-glucopyranosyl] P2-dolichyl diphosphate (N-acetylhyalobiosyluronic dolichyl diphosphate)

Starting from 2-acetamido-4,6-di-O-acetyl-2-deoxy-3-O-(methyl 2,3,4-tri-O-acetyl-β-D-glucopyranosyluronate)-α-D-glucopyranose (20), a crystalline intermediate prepared by a conventional sequence of reactions, the total synthesis of N-acetyl-hyalobiosyluronic dolichyl diphosphate was achieved. One of the key steps involved the transformation of the disaccharide 20 into the methyloxazoline 26, which was then converted into the stable, crystalline disaccharide phosphate derivative in ～30% yield. The methyloxazoline 26 was directly prepared from the corresponding methyl α-glycoside by acetolysis. Similarly, the allyl α-glycoside was transformed into 26.     

One-pot enzymatic production of 2-acetamido-2-deoxy-D-galactose (GalNAc) from 2-acetamido-2-deoxy-D-glucose (GlcNAc)

2-Acetamido-2-deoxy-D-galactose (GalNAc) is a common monosaccharide found in biologically functional sugar chains, but its availability is often limited due to the lack of abundant natural sources. In order to produce GalNAc from abundantly available sugars, 2-acetamido-2-deoxy-D-glucose (GlcNAc) was converted to GalNAc by a one-pot reaction using three enzymes involved in the galacto-N-biose/lacto-N-biose I pathway of bifidobacteria. Starting the reaction with 600 mM GlcNAc, 170 mM GalNAc was produced at equilibrium in the presence of catalytic amounts of ATP and UDP-Glc under optimized conditions. GalNAc was separated from GlcNAc using water-eluting cation-exchange chromatography with a commonly available cation-exchange resin.     

Synthesis of three disaccharides for the preparation of immunogens bearing immunodeterminants known to occur on glycoproteins

p-Nitrophenyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-beta-D-glucopyranoside was condensed with 2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl bromide, the product deprotected, and the disaccharide glycoside converted into p-trifluoroacetamidophenyl 2-acetamido-2-deoxy-4-O-beta-D-galactopyranosyl-beta- D-glucopyranoside. p-Nitrophenyl 3-O-benzoyl-4,6-di-O-benzylidene-alpha-D-mannopyranoside was condensed with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl bromide, and the product was deprotected, to yield p-nitrophenyl 2-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-alpha-D-mannopyranoside. p-Nitrophenyl 2-acetamido-3,4-di-O-benzoyl-2-deoxy-beta-D-glucopyranoside was condensed with 2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl bromide, and, after reduction, trifluoroacetylation, and deprotection, p-trifluoroacetamidophenyl 2-acetamido-2-deoxy-6-O-alpha-L-fucopyranosyl-beta-D-glucopyranoside was obtained.     

Synthesis and utility of sulfated chromogenic carbohydrate model substrates for measuring activities of mucin-desulfating enzymes

A chromogenic substrate, 4-nitrophenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside 6-sodium sulfate was synthesized and used in combination with beta-N-acetylhexosaminidase for detection of the sulfatase, MdsA, by release of 4-nitrophenol. MdsA was originally isolated from the bacterium Prevotella strain RS2 and is believed to be involved in desulfation of sulfomucins, major components of the mucus barrier protecting the human colon surface. The exo nature of the MdsA sulfatase was indicated by its inability to de-esterify the disaccharide 4-nitrophenyl beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-beta-D-glucopyranoside 6-sodium sulfate. This latter compound was prepared from monosaccharide precursors by two different methods, the shorter requiring just six steps from 4-nitrophenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside and giving an overall yield of 26.4%. The syntheses of 4-nitrophenyl beta-D-galactopyranoside 3-triethylammonium sulfate and 6-triethylammonium sulfate and their use in combination with beta-galactosidase as chromogenic substrates for detecting Bacteroides fragilis sulfatases with different specificities was also demonstrated.