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PubMed1987

Characterization of the products generated from oversulphated dermatan sulphate isomers with chondroitinase-B by high-performance liquid chromatography.

Characterization with specific chondroitinase-B of the constituents of the unsaturated sulphated disaccharides generated from variously sulphated dermatan sulphate (DS) isomers in human kidney tissues was carried out by high-performance liquid chromatography, using a sulphonized styrene-divinylbenzene copolymer. The products derived from the variously sulphated DS isomers with the chondroitinase-B at specific unsaturated disaccharides were characterized as unsaturated mono-, di- and trisulphated disaccharides. The results suggest that chondroitinase-B converts DS isomers into unsaturated 4-sulphated disaccharide, unsaturated disulphated disaccharides types B and H (delta Di-diSB and delta Di-diSH) and unsaturated trisulphated disaccharide (delta Di-triS), which possess sulphate linkage (s) at position 4 of the galactosamine residues and, in addition, at position 6 of galactosamine and/or position 2 of iduronic acid. The delta Di-diSB, delta Di-diSH and delta Di-triS were found for the first time in human kidney tissue.

Chondroitin↗
PubMed2002

An efficient and practical synthesis of beta-(1 --> 3)-linked xylooligosaccharides.

A facile and practical method was developed for the synthesis of beta-(1 --> 3)-linked xylooligosaccharides. Dibezoylation of allyl alpha-D-xylopyranoside (1) afforded 2,4-dibenzoate 6 as the major product. Chloroacetylation of 6, followed by deallylation and trichloroacetimidation, gave a 1:3 alpha/beta imidate (10 and 11) mixture. Coupling of the imidate mixture with 6 gave a disaccharide 13, whose dechloroacetylation afforded the disaccharide acceptor 16. Condensation of perbenzoylated xylosyl alpha/beta imidate (7 and 8) mixture with 6 gave the disaccharide 12. Deallylation of 12, followed by trichloroacetimidation, furnished the disaccharide donor as a 1:1 alpha/beta mixture. Coupling of the disaccharide donor mixture with the disaccharide acceptor 16 yielded the tetrasaccharide 17. Reiteration of deallylation and trichloroacetimidation transformed 17 to the tetrasaccharide donor mixture. Condensation of the tetrasaccharide donor mixture with the acceptor 16 gave the hexasaccharide 21. Debenzoylation with saturated ammonia-methanol afforded beta-(1 --> 3)-linked allyl xylotetraoside and xylohexaoside.

Carbohydrate Conformation↗
PubMed1998

Mechanism of heparin activation of antithrombin: evidence for an induced-fit model of allosteric activation involving two interaction subsites.

The anticoagulant activation of the serpin antithrombin by heparin pentasaccharide DEFGH was previously shown to involve trisaccharide DEF first binding and inducing activation of the serpin, followed by disaccharide GH binding and stabilizing the activated state [Petitou et al. (1997) Glycobiology 7, 323-327; Desai et al. (1998) J. Biol. Chem. 273, 7478-7487]. In the present study, the role of conformational changes and charged residues of the GH disaccharide in the allosteric activation mechanism was investigated with variant pentasaccharides modified in the GH disaccharide. Perturbation of the conformational equilibrium of iduronate residue G through replacement of the nonessential 3-OH of this residue with -H resulted in parallel decreases in the fraction of residue G in the skew boat conformer (from 64 to 24%) and in the association constant for pentasaccharide binding to antithrombin [(2.6 +/- 0.3)-fold], consistent with selective binding of the skew boat conformer to the serpin. Introduction of an additional sulfate group to the 3-OH of residue H flanking a putative charge cluster in the GH disaccharide greatly enhanced the affinity for the serpin by approximately 35-fold with only a small increase in the fraction of residue G in the skew boat conformation (from 64 to 85%). The salt dependence of binding, together with a recent X-ray structure of the antithrombin-pentasaccharide complex, suggested that the majority of the enhanced affinity of the latter pentasaccharide was due to direct electrostatic and hydrogen-bonding interactions of the H residue 3-O-sulfate with antithrombin. All variant pentasaccharides produced a normal enhancement of antithrombin fluoresence and normal acceleration of factor Xa inhibition by the serpin at saturating levels, indicating that conformational activation of antithrombin was not affected by the pentasaccharide modifications. Rapid kinetic studies were consistent with the altered affinities of the variant pentasaccharides resulting mostly from perturbed interactions of the reducing-end GH disaccharide with the activated antithrombin conformation and minimally to an altered binding of the nonreducing-end DEF trisaccharide to the native serpin conformation. Together, these results support a model in which the conformational flexibility of the G residue facilitates conversion to the skew boat conformer and thereby allows charged groups of the GH disaccharide to bind and stabilize the activated antithrombin conformation that is induced by the DEF trisaccharide.

Allosteric Regulation↗
PubMed1997

Total Synthesis of Tricolorin A.

Tricolorin A (1) is a novel tetrasaccharide macrolactone that is a natural herbicide. In this paper is reported a total synthesis of 1. Coupling of hydroxy ester 18 with D-fucosyl trichloroacetimidate 23 gave fucoside 24. Removal of the C-2 pivaloyl group of 24 followed by coupling with D-glucosyl trichloroacetimidate 29 resulted in isolation of disaccharide 30. Saponification of the ester groups of 30 and subsequent selective macrolactonization of the acid diol 31 by the Yonemitsu protocol gave only the desired lactone 32. The key step in the assembly of disaccharide glycosyl trichloroacetimidate 52 was coupling L-rhamnoside 47 with L-rhamnosyl trichloroacetimidate 43. Attempts to couple lactone disaccharide 32 with disaccharide 52 were unsuccessful. Using an alternate plan for assembly of the tetrasaccharide, reaction of disaccharide glycosyl trichloroacetimidate 58 with disaccharide 37 gave tetrasaccharide 59. Diester lactone 63 was generated by selective macrolactonization of tetrasaccharide acid triol 60, again using the Yonemitsu protocol, followed by addition of the chiral side chain acid to the reaction vessel. Synthetic tricolorin A (1) was obtained by deprotection of 63. Starting from fucose, glucose, rhamnose, and (S)-1-octyn-3-ol, the synthesis required 39 steps overall. The longest linear sequence was 14 steps, with an overall yield for this longest linear sequence of 6%.

Journal Article↗
PubMed1998

Characterization of a low-sulfated chondroitin sulfate from the body of Viviparus ater (mollusca gastropoda). Modification of its structure by lead pollution.

A chondroitin sulfate was purified from the body of Viviparus ater(Mollusca gastropoda) and analyzed for molecular mass, constituent disaccharides, and structure by 1H NMR and 1H 2D NMR. A quite unique glycosaminoglycan species was isolated having a high molecular mass (greater than 45,000) and low charge density, about 0.60, due to the presence of 42% non-sulfated disaccharide, 5% 6-sulfated disaccharide, 48% 4-sulfated disaccharide, and 5% 4,6-disulfated disaccharide. Specimens of Mollusca were also submitted to lead exposure for different times, and the effect on chondroitin sulfate structure was studied. After 96 h treatment a strong decrease in chondroitin sulfate content was observed with a significant modification of its structure producing a more desulfated polymer, in particular in position 4 of the galactosamine unit. Simultaneously, the amount of unsaturated non-sulfated disaccharide increased with an overall decrease of the charge density.

Animals↗
PubMed1999

Dynamic epigenetic regulation of initial O-glycosylation by UDP-N-Acetylgalactosamine:Peptide N-acetylgalactosaminyltransferases. site-specific glycosylation of MUC1 repeat peptide influences the substrate qualities at adjacent or distant Ser/Thr positions.

In search of possible epigenetic regulatory mechanisms ruling the initiation of O-glycosylation by polypeptide:N-acetylgalactosaminyltransferases, we studied the influences of mono- and disaccharide substituents of glycopeptide substrates on the site-specific in vitro addition of N-acetylgalactosamine (GalNAc) residues by recombinant GalNAc-Ts (rGalNAc-T1, -T2, and -T3). The substrates were 20-mers (HGV20) or 21-mers (AHG21) of the MUC1 tandem repeat peptide carrying GalNAcalpha or Galbeta1-3GalNAcalpha at different positions. The enzymatic products were analyzed by MALDI mass spectrometry and Edman degradation for the number and sites of incorporated GalNAc. Disaccharide placed on the first position of the diad Ser-16-Thr-17 prevents glycosylation of the second, whereas disaccharide on the second position of Ser-16-Thr-17 and Thr-5-Ser-6 does not prevent GalNAc addition to the first. Multiple disaccharide substituents suppress any further glycosylation at the remaining sites. Glycosylation of Ser-16 is negatively affected by glycosylation at position -6 (Thr-10) or -10 (Ser-6) and is inhibited by disaccharide at position -11 (Thr-5), suggesting the occurrence of glycosylation-induced effects on distant acceptor sites. Kinetic studies revealed the accelerated addition of GalNAc to Ser-16 adjacent to GalNAc-substituted Thr-17, demonstrating positive regulatory effects induced by glycosylation on the monosaccharide level. These antagonistic effects of mono- and disaccharides could underlie a postulated regulatory mechanism.

Acetylgalactosamine↗
PubMed2003

The low sulfated chondroitin sulfate proteoglycans of human placenta have sulfate group-clustered domains that can efficiently bind Plasmodium falciparum-infected erythrocytes.

Plasmodium falciparum infection in pregnant women results in the chondroitin 4-sulfate-mediated adherence of the parasite-infected red blood cells (IRBCs) in the placenta, adversely affecting the health of the fetus and mother. We have previously shown that unusually low sulfated chondroitin sulfate proteoglycans (CSPGs) in the intervillous spaces of the placenta are the receptors for IRBC adhesion, which involves a chondroitin 4-sulfate motif consisting of six disaccharide moieties with approximately 30% 4-sulfated residues. However, it was puzzling how the placental CSPGs, which have only approximately 8% of the disaccharide 4-sulfated, could efficiently bind IRBCs. Thus, we undertook to determine the precise structural features of the CS chains of placental CSPGs that interact with IRBCs. We show that the placental CSPGs are a mixture of two major populations, which are similar by all criteria except differing in their sulfate contents; 2-3% and 9-14% of the disaccharide units of the CS chains are 4-sulfated, and the remainder are nonsulfated. The majority of the sulfate groups in the CSPGs are clustered in CS chain domains consisting of 6-14 repeating disaccharide units. While the sulfate-rich regions of the CS chains contain 20-28% 4-sulfated disaccharides, the other regions have little or no sulfate. Further, we find that the placental CSPGs are able to efficiently bind IRBCs due to the presence of 4-sulfated disaccharide clusters. The oligosaccharides corresponding to the sulfate-rich domains of the CS chains efficiently inhibited IRBC adhesion. Thus, our data demonstrate, for the first time, the unique distribution of sulfate groups in the CS chains of placental CSPGs and that these sulfate-clustered domains have the necessary structural elements for the efficient adhesion of IRBCs, although the CS chains have an overall low degree of sulfation.

Animals↗
PubMed2006

Effect of diglucosamine on the entrapment of protein into liposomes.

Liposomes, which had entrapped bovine serum albumin (BSA), were modified with diglucosamine by two methods. The liposome was prepared by a freeze-thawing method in the presence of the disaccharide, or the disaccharide was added to the liposome prepared in advance without it. To examine the effects of diglucosamine, the morphology, mean particle size, and zeta potential of both liposomes were compared with those of BSA-entrapping liposome prepared without the disaccharide. Diglucosamine caused no remarkable change in shape and no aggregation of the liposome. The presence of the disaccharide was confirmed on the surfaces of modified liposomes, and the entrapment of BSA into the liposomes was increased by the disaccharide. The entrapment behavior was affected by the way the disaccharide was added, and the difference in the way the BSA was entrapped was also indicated.

Animals↗
PubMed1991

Structural analysis of the lipid A component of Campylobacter jejuni CCUG 10936 (serotype O:2) lipopolysaccharide. Description of a lipid A containing a hybrid backbone of 2-amino-2-deoxy-D-glucose and 2,3-diamino-2,3-dideoxy-D-glucose.

The chemical structure of Campylobacter jejuni CCUG 10936 lipid A was elucidated. The hydrophilic backbone of the lipid A was shown to consist of three (1----6)-linked bisphosphorylated hexosamine disaccharides. Neglecting the phosphorylation pattern, a D-glucosamine (2-amino-2-deoxy-D-glucose) disaccharide [beta-D-glucosaminyl-(1----6)-D-glucosamine], a hybrid disaccharide of 2,3-diamino-2,3-dideoxy-D-glucose and D-glucosamine [2,3-diamino-2,3-dideoxy-beta-D-glucopyranosyl-(1----6)-D-glucosamine], and a 2,3-diamino-2,3-dideoxy-D-glucose disaccharide were present in a molar ratio of 1:6:1.2. Although the backbones are bisphosphorylated, heterogeneity exists in the substitution of the polar head groups. Phosphorylethanolamine is alpha-glycosidically bound to the reducing sugar residue of the backbone, though C-1 is also non-stoichiometrically substituted by diphosphorylethanolamine. Position 4' of the non-reducing sugar residue carries an ester-bound phosphate group or is non-stoichiometrically substituted by diphosphorylethanolamine. By methylation analysis it was shown that position 6' is the attachment site for the polysaccharide moiety in lipopolysaccharide. These backbone species carry up to six molecules of ester- and amide-bound fatty acids. Four molecules of (R)-3-hydroxytetradecanoic acid are linked directly to the lipid A backbone (at positions 2, 3, 2', and 3'). Laser desorption mass spectrometry showed that both (R)-3-hydroxytetradecanoic acids linked to the non-reducing sugar unit carry, at their 3-hydroxyl group, either two molecules of hexadecanoic acid or one molecule of tetradecanoic and one of hexadecanoic acid. It also suggested that the (R)-3-(tetradecanoyloxy)-tetradecanoic acid was attached at position 2', whereas (R)-3-(hexadecanoyloxy)-tetradecanoic acid was attached at position 3', or at positions 2' and 3'. Therefore, the occurrence of three backbone disaccharides differing in amino sugar composition and presence of a hybrid disaccharide differentiate the lipid A of this C. jejuni strain from enterobacterial and other lipids A described previously.

Campylobacter jejuni↗
PubMed2006

Keratan sulfate and chondroitin/dermatan sulfate in maximally recovered hypocellular stromal interface scars of postmortem human LASIK corneas.

PURPOSE: To analyze the amounts and distributions of nonsulfated and sulfated keratan sulfate (KS) and chondroitin/dermatan sulfate (CS/DS) disaccharides in the interface wound of human postmortem LASIK corneas in comparison with normal control corneas. METHODS: Corneal stromal tissue samples from central and paracentral hypocellular primitive stromal interface scars of human LASIK corneas and from similar regions of normal control corneas were collected by laser capture microdissection (LCM) and subsequently were digested with specific glycosidase enzymes. Digests were directly analyzed by electrospray ionization tandem mass spectrometry (ESI-MS/MS). RESULTS: Concentrations of both monosulfated GlcNAc(6S)-beta-1,3-Gal (MSD2) and disulfated Gal (6S)-beta-1,4-GlcNAc(6S) (DSD) KS disaccharides from the LASIK interface scars were significantly lower than in normal control corneal stromas. No significant difference was found for the concentration of nonsulfated (NSD) KS disaccharides in LASIK interface scars compared with normal controls. The concentration of DeltaUA-beta-1,3-GalNAc(6S) (Deltadi-6S) CS/DS disaccharides from the LASIK interface scar was significantly higher than normal corneal stroma, whereas concentrations of DeltaUA-beta-1,3-GalNAc(4S) (Deltadi-4S) and nonsulfated Deltadi-0S CS/DS disaccharides demonstrated no significant differences from normal corneas. CONCLUSIONS: The profiles of KS and CS/DS disaccharides in LASIK interface scars are significantly different from those in normal cornea stromal tissue, as revealed by LCM and ESI-MS/MS.

Chondroitin Sulfates↗
PubMedDate not supplied

Differential binding properties of Gal/GalNAc specific lectins available for characterization of glycoreceptors.

Differentiating the binding properties of applied lectins should facilitate the selection of lectins for characterization of glycoreceptors on the cell surface. Based on the binding specificities studied by inhibition assays of lectin-glycan interactions, over twenty Gal and/or GalNAc specific lectins have been divided into eight groups according to their specificity for structural units (lectin determinants), which are the disaccharide as all or part of the determinants and of GalNAc alpha 1-->Ser (Thr) of the peptide chain. A scheme of codes for lectin determinants is illustrated as follows: (1) F (GalNAc alpha 1-->3GalNAc), Forssman specific disaccharide--Dolichos biflorus (DBL), Helix pomatia (HPL) and Wistaria floribunda (WFL) lectins. (2) A (GalNAc alpha 1-->3 Gal), blood group A specific disaccharide--Codium fragile subspecies tomentosoides (CFT), Soy bean (SBL), Vicia villosa-A4 (VVL-A4), and Wistaria floribunda (WFL) lectins. (3) Tn (GalNAc alpha 1-->Ser (Thr) of the protein core)--Vicia villosa B4 (VVL-B4), Salvia sclarea (SSL), Maclura pomifera (MPL), Bauhinia purpurea alba (BPL) and Artocarpus integrifolia (Jacalin, AIL). (4) T (Gal beta 1-->3GalNAc), the mucin type sugar sequences on the human erythrocyte membrane(T alpha), T antigen or the disaccharides at the terminal nonreducing end of gangliosides (T beta)--Peanut (PNA), Bauhinia purpurea alba (BPL), Maclura pomifera (MPL), Sophora japonica (SJL), Artocarpus lakoocha (Artocarpin) lectins and Abrus precatorius agglutinin (APA).(5) I and II (Gal beta 1-->3(4)GlcNAc)--the disaccharide residue at the nonreducing end of the carbohydrate chains derived from either N- or O-glycosidic linkage--Ricinus communis agglutinin (RCA1), Datura stramonium (TAL, Thorn apple), Erythrina cristagalli (ECL, Coral tree), and Geodia cydonium (GCL). (6) B (Gal alpha 1-->3Gal), human blood group B specific disaccharide--Griffonia(Banderiaea) simplicifolia B4 (GSI-B4). (7) E (Gal alpha 1-->4Gal), receptors for pathogenic E. coli agglutinin, Shiga toxin and Mistletoe toxic lectin-I (ML-I) and abrin-a.

Acetylgalactosamine↗
PubMed1988

Localization and catabolism of cyanogenic glycosides.

The catabolism of cyanogenic glycosides is initiated by cleavage of the carbohydrate moiety by one or more beta-glycosidases, which yields the corresponding alpha-hydroxynitrile. Until recently, the mode by which cyanogenic disaccharides are hydrolysed was largely unclear. Investigation of highly purified beta-glycosidases from plants containing cyanogenic disaccharides has now indicated that these compounds may be degraded via two distinct pathways, depending on the plant species. beta-Glycosidases from Davallia trichomanoides and Vicia angustifolia hydrolysed (R)-vicianin and (R)-amygdalin at the aglycone-disaccharide bond producing mandelonitrile and the corresponding disaccharide. Alternatively, hydrolysis of cyanogenic disaccharides in Prunus serotina, almonds, and Linum usitatissimum involves stepwise removal of the sugar residues. The nature of these enzymes and of other beta-glycosidases responsible for hydrolysis of simple cyanogenic monosaccharides is discussed. Hydroxynitriles may decompose either spontaneously or enzymically in the presence of a hydroxynitrile lyase to produce hydrogen cyanide and an aldehyde or ketone. The major kinetic and molecular properties of hydroxynitrile lyases purified from species accumulating aromatic and aliphatic cyanogens are reviewed. Cyanogenesis occurs rapidly only after cyanogenic plant tissues are macerated, allowing glycosides access to their catabolic enzymes. The possible nature of the compartmentation which prevents cyanogenesis under normal physiological conditions is discussed in relation to our knowledge of the tissue and subcellular localizations of cyanogens and catabolic enzymes.

Aldehyde-Lyases↗
PubMed1983

Synthesis of methyl 3-O- and 2-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-alpha D-galactopyranoside.

Condensation of methyl 2-O-benzoyl-4,6-O-benzylidene-alpha-D-galactopyranoside with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl bromide (1) in dichloromethane, in the presence of silver trifluoromethanesulfonate, 2,4,6-trimethylpyridine, and molecular sieves, afforded methyl 2-O-benzoyl-4,6-O-benzylidene-3-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalim ido- beta-D-glucopyranosyl)-alpha-D-galactopyranoside (4). Deacetalation of 4 in hot, 80% aqueous acetic acid gave methyl 2-O-benzoyl-3-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido- beta-D-glucopyranosyl)-alpha-D-galactopyranoside (5), which, on deacylation, followed by peracetylation, furnished the peracetylated disaccharide derivative (6). The structures of 5 and 6 were established by 1H-n.m.r. spectroscopy. O-Deacetylation of 6 afforded the title beta-(1 leads to 3)-linked disaccharide 7. For the synthesis of the beta-(1 leads to 2)-linked isomer, methyl 3-O-benzoyl-4,6-O-benzylidene-alpha-D-galactopyranoside was similarly condensed with bromide 1 to give the fully protected disaccharide derivative (8). Cleavage of the benzylidene group of 8 gave methyl 3-O-benzoyl-2-O-(3,4,6- tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-alpha-D- galactopyranoside (9). Deacetylation of 9, followed by peracetylation, afforded the peracetate (10). O-Deacetylation of 10 gave the beta-(1 leads to 2)-linked disaccharide (11). The structures of the disaccharides 7 and 11 were confirmed by 13C-n.m.r. spectroscopy.

Blood Group Antigens↗
PubMed1976

On the structure of heparitin sulfates. Analyses of the products formed from heparitin sulfates by two heparitinases and a heparinase from Flavobacterium heparinum.

The analyses of the products formed from heparitin sulfates by the action of two heparitinases and a heparinase from Flavorbacterium heparinum is reported. Heparitin sulfates A and B are degraded by heparitinase I yielding two disaccharides, one of them composed of N-acetylucosamine and an unsaturated uronic, joined by alpha(1 lead to 4) linkage, and the other, with the same composition but with an O-sulfate at the hexosamine moiety. A third disaccharide is also formed from heparitin sulfate B, by the action of the same enzyme, composed of glucosamine N-sulfate and an unsaturated uronic acid joined probably by alpha(1 lead to 4) linkage. Besides these three disaccharides, heparitin sulfate B yields, by the action of heparitinase I, an oligosaccharide (with an average molecular weight of 6000) which is completely degraded by the heparitinase II yielding a disaccharide composed of glucosamine 2,6-disulfate and unsaturated uronic acid. All the disaccharides are further degraded by alpha-glycuronidase from Flavobacterium heparinum yielding the respective monosaccharides. Based on these and other analyses the possible structures of the heparitin sulfates are proposed.

Acetylglucosamine↗
PubMed2005

Characterization of heparan sulfate from the unossified antler of Cervus elaphus.

The antler is the most rapidly growing tissue in the animal kingdom. According to previous reports, antler glycosaminoglycans (GAGs) consist of all kinds GAGs except for heparan sulfate (HS). Chondroitin sulfate is the major antler GAG component comprising 88% of the total uronic acid content. In the current study, we have isolated HS from antler for the first time and characterized it based on both NMR spectroscopy and disaccharide composition analysis. Antler GAGs were isolated by protease treatment and followed by cetylpyridinium chloride precipitation. The sensitivity of antler GAGs to heparin lyase III showed that this sample contained heparan sulfate. After incubation of antler GAGs with chondroitin lyase ABC, the HS-containing fraction was recovered by ethanol precipitation. The composition of HS disaccharides in this fraction was determined by its complete depolymerization with a mixture of heparin lyase I, II, and III and analysis of the resulting disaccharides by the reversed-phase (RP) ion pairing-HPLC, monitored by the fluorescence detection using 2-cyanoacetamide as a post-column labeling reagent. Eight unsaturated disaccharides (DeltaUA-GlcNAc, DeltaUA-GlcNS, DeltaUA-GlcNAc6S, DeltaUA2S-GlcNAc, DeltaUA-GlcNS6S, DeltaUA2S-GlcNS, DeltaUA2S-GlcNAc6S, DeltaUA2S-GlcNS6S) were produced from antler HS by digestion with the mixture of heparin lyases. The total content of 2-O-sulfo disaccharide units in antler HS was higher than that of heparan sulfate from most other animal sources.

Animals↗
PubMed2005

Alternansucrase acceptor reactions with D-tagatose and L-glucose.

Alternansucrase (EC 2.4.1.140) is a d-glucansucrase that synthesizes an alternating alpha-(1-->3), (1-->6)-linked d-glucan from sucrose. It also synthesizes oligosaccharides via d-glucopyranosyl transfer to various acceptor sugars. Two of the more efficient monosaccharide acceptors are D-tagatose and L-glucose. In the presence of d-tagatose, alternansucrase produced the disaccharide alpha-d-glucopyranosyl-(1-->1)-beta-D-tagatopyranose via glucosyl transfer. This disaccharide is analogous to trehalulose. We were unable to isolate a disaccharide product from L-glucose, but the trisaccharide alpha-D-glucopyranosyl-(1-->6)-alpha-d-glucopyranosyl-(1-->4)-l-glucose was isolated and identified. This is analogous to panose, one of the structural units of pullulan, in which the reducing-end D-glucose residue has been replaced by its L-enantiomer. The putative L-glucose disaccharide product, produced by glucoamylase hydrolysis of the trisaccharide, was found to be an acceptor for alternansucrase. The disaccharide, alpha-D-glucopyranosyl-(1-->4)-L-glucose, was a better acceptor than maltose, previously the best known acceptor for alternansucrase. A structure comparison of alpha-D-glucopyranosyl-(1-->4)-L-glucose and maltose was performed through computer modeling to identify common features, which may be important in acceptor affinity by alternansucrase.

Binding Sites↗
PubMed1996

The synthesis of galactopyranosyl derivatives with beta-galactosidases of different origins.

beta-Galactosidases from four different sources were used to catalyze the transfer of beta-D-galactopyranosyl from 4-nitrophenyl-beta-D-galactopyranoside to a hydroxyl group of 2-acetamido-2-deoxy-galactopyranose in the synthesis of Gal beta (1-3)GalNAc (1), Gal beta (1-4)GalNAc (2) and Gal beta (1-6)GalNAc (3), in triethyl phosphate buffered solutions (20-60%). When beta-galactosidases from Penicillium multicolor and Aspergillus oryzae were used as the catalysts, the beta (1-6)-linked disaccharide was produced as the major product. However, with beta-galactosidase from Bifidobacterium bifidum, the major products were the beta (1-4) and beta (1-6)-linked disaccharides. On the other hand, with beta-galactosidase from Streptococcus 6646K, beta (1-3)-linked disaccharide was predominant together with beta (1-4)-linked isomer. Gal beta (1-3)GlcNAc (4), Gal beta (1-4)GlcNAc (5) and Gal beta (1-6)GlcNAc (6) were also synthesized with beta-galactosidase from S. 6646K and B. bifidum with 2-acetamido-2-deoxy-glucopyranose as the acceptor and PNPGal as the donor. In both cases, the beta (1-4)-linked disaccharide was predominantly produced. In addition, a comparative study was carried out to determine the regioselectivity of the transglycosylation reaction as well as the hydrolytic specificity toward the same linked disaccharides.

Acetylgalactosamine↗
PubMed2001

Solution structure of a cyanovirin-N:Man alpha 1-2Man alpha complex: structural basis for high-affinity carbohydrate-mediated binding to gp120.

BACKGROUND: Cyanovirin-N (CVN) is a novel, 11 kDa cyanobacterial protein that potently inhibits viral entry by diverse strains of HIV through high-affinity carbohydrate-mediated interactions with the viral envelope glycoprotein gp120. CVN contains two symmetry-related carbohydrate binding sites of differing affinities that selectively bind to Man(8) D1D3 and Man(9) with nanomolar affinities, the carbohydrates that also mediate CVN:gp120 binding. High-resolution structural studies of CVN in complex with a representative oligosaccharide are desirable for understanding the structural basis for this unprecedented specificity. RESULTS: We have determined by multidimensional heteronuclear NMR spectroscopy the three-dimensional solution structure of CVN in complex with two equivalents of the disaccharide Manalpha1-2Manalpha, a high-affinity ligand which represents the terminal-accessible disaccharide present in Man(8) D1D3 and Man(9). The structure reveals that the bound disaccharide adopts the stacked conformation, thereby explaining the selectivity for Man(8) D1D3 and Man(9) over other oligomannose structures, and presents two novel carbohydrate binding sites that account for the differing affinities of the two sites. The high-affinity site comprises a deep pocket that nearly envelops the disaccharide, while the lower-affinity site comprises a semicircular cleft that partially surrounds the disaccharide. The approximately 40 A spacing of the two binding sites provides a simple model for CVN:gp120 binding. CONCLUSIONS: The CVN:Manalpha1-2Manalpha complex provides the first high-resolution structure of a mannose-specific protein-carbohydrate complex with nanomolar affinity and presents a new carbohydrate binding motif, as well as a new class of carbohydrate binding protein, that facilitates divalent binding via a monomeric protein.

Amino Acid Sequence↗