Carbohydrate-protein Linkage Region Research Articles

Structural variation in the linkage region of pharmaceutical heparin arising from oxidative treatments during manufacture

During the manufacture of pharmaceutical heparin, a range of treatments are applied to sanitize, decolourise and reduce the pyrogenic properties of the samples. The structural effects of bleaching, an oxidative process, are examined. Among 1H and 13C NMR signals ascribable to the tetrasaccharide linkage region of heparin, samples of porcine mucosal heparin frequently display characteristic signals at chemical shift values of 4.5 and 106 ppm respectively, which have not been explained previously. Fractions enriched with material reporting this signal were isolated from heparinase digested porcine mucosal heparin samples and subjected to analysis using mass spectrometry and NMR spectroscopy. A novel structure, ΔU-Gal-Gal-Xyl–CH2–CONH2, was identified by mass fragmentation experiments and further interesting structural motifs emerged following evaluation by mass spectrometry of longer oligosaccharide chains biosynthesized away from the linker tetrasaccharide, GlcA-Gal-Gal-Xyl. The carbohydrate-protein linkage region is thus affected by the bleaching step involved in the manufacturing process of heparin. The discovery of specific modifications that reflect the extent of the oxidation treatment adopted is relevant to the monitoring of inadvertent damage to the heparin structure during manufacture that contributes to sample variation and which could also lead to reduced drug quality.

Tandem mass spectrometry for the characterisation of sulphated‐phosphorylated analogues of the carbohydrate–protein linkage region of proteoglycans

Carbohydrate-protein linkage region of proteoglycans is a key oligosaccharide structure because their sulphated and/or phosphorylated analogues control the biosynthesis of glucosaminoglycans or galactosaminoglycans. Therefore, synthesised sulphated and/or phosphorylated analogues were characterised by tandem mass spectrometry in the negative-ion mode. Results demonstrated that the product ion profile was characterised by glycosidic and cross-ring cleavages depending on the position and the type of the charged group (sulphate, phosphate or carboxylate). When the above compounds were sulphated and phosphorylated, the ion found at m/z 79 was the only one that demonstrated a phosphate group on the structure. The data also suggested that when a sodium cation was present in a sulphated and phosphorylated structure, the phosphate group in most cases was neutralised by the sodium cation, and therefore cleaved off the molecule, while the sulphate group was carrying the negative charge.

A novel type of carbohydrate-protein linkage region in the tyrosine-bound S-layer glycan of Thermoanaerobacterium thermosaccharolyticum D120-70.

The surface-layer (S-layer) protein of Thermoanaerobacterium thermosaccharolyticum D120-70 contains glycosidically linked glycan chains with the repeating unit structure -->4)[alpha-D-Galp-(1-->2)]-alpha-L-Rhap-(1-->3)[beta-D-Glcp-(1--> 6)] -beta-D-Manp-(1-->4)-alpha-L-Rhap-(1-->3)-alpha-D-Glcp-(1--> . After proteolytic degradation of the S-layer glycoprotein, three glycopeptide pools were isolated, which were analyzed for their carbohydrate and amino-acid compositions. In all three pools, tyrosine was identified as the amino-acid constituent, and the carbohydrate compositions corresponded to the above structure. Native polysaccharide PAGE showed the specific heterogeneity of each pool. For examination of the carbohydrate-protein linkage region, the S-layer glycan chain was partially hydrolyzed with trifluoroacetic acid. 1D and 2D NMR spectroscopy, including a novel diffusion-edited difference experiment, showed the O-glycosidic linkage region beta-D-glucopyranose-->O-tyrosine. No evidence was found of additional sugars originating from a putative core region between the glycan repeating units and the S-layer polypeptide. For the determination of chain-length variability in the S-layer glycan, the different glycopeptide pools were investigated by matrix-assisted laser desorption ionization-time of flight mass spectrometry, revealing that the degree of polymerization of the S-layer glycan repeats varied between three and 10. All masses were assigned to multiples of the repeating units plus the peptide portion. This result implies that no core structure is present and thus supports the data from the NMR spectroscopy analyses. This is the first observation of a bacterial S-layer glycan without a core region connecting the carbohydrate moiety with the polypeptide portion.

Molecular structure of the carbohydrate-protein linkage region fragments from connective-tissue proteoglycans

Molecular structure of the carbohydrate-protein linkage region fragments from connective-tissue proteoglycans

NMR and molecular modeling studies on two glycopeptides from the carbohydrate-protein linkage region of connective tissue proteoglycans.

Complete 1H and 13C NMR assignments are reported for two glycopeptides representing the carbohydrate-protein linkage region of connective tissue proteoglycans. These glycopeptides are the octasaccharide hexapeptide, Ser(GlcpAbeta(1-->3) Galpbeta(1-->3)Galpbeta(1-->4)Xylpbeta)-Gly-Ser-Gly-Se r (GlcpAbeta(1-->3)Galpbeta(1-->3)Galpbeta(1-->4)Xylp beta)-Gly (1), and the tetrasaccharide dipeptide, Ser(GlcpAbeta(1-->3)Galpbeta(1-->3)Galpbeta(1-->4)X ylpbeta)-Gly (2). The vicinal coupling constant data show that the monosaccharide residues adopt4 C 1 chair conformations. Distance geometry/simulated annealing calculations using 2D NOESY derived distance constraints yielded a single family of structures for the tetrasaccharide moiety, with well defined interglycosidic linkage conformations. The straight phi torsion angles of the glycosidic C1'-O1 bonds showed a strict preference for the -sc range whereas the psi torsion angles (O1-Cn) exhibited dependence upon the interglycosidic linkage position (-ac for beta(1-->3) linkage, +ac for beta(1-->4) linkage). The predominant conformation about the glycopeptide bond is straight phi = -sc and psi = +ac. The presence of strong daN (i, i+1) NOE contacts, and the general absence of dNN (i, i+1) contacts (except for a weak Ser-5/Gly-6 dNN contact) and the dbN (i, i+1) contacts (except for Ser-1/Gly-2) in the ROESY spectrum, suggest that the backbone for 1 is predominantly in an extended conformation. A comparison of the ROESY data for 1 with those obtained from the unglycosylated hexapeptide (3) of the same sequence suggests that glycosylation has only a marginal influence on the backbone conformation of the hexapeptide.

Structure determination for octasaccharides derived from the carbohydrate-protein linkage region of chondroitin sulphate chains in the proteoglycan aggrecan from bovine articular cartilage.

Five octasaccharides derived from the protein carbohydrate linkage region of chondroitin sulphate (CS) have been isolated from the large aggregating proteoglycan (aggrecan) extracted from the bovine articular cartilage of 6-year-old to 8-year-old animals. Following the purification of aggrecan the attached CS chains were digested with CS ABC endolyase and subsequently released from the protein core by beta-elimination. The individual oligosaccharides were purified by strong anion-exchange chromatography and their structures determined by very high-field one-dimensional and two-dimensional 1H-NMR spectroscopy. They were found to be octasaccharides, comprised of tetrasaccharide repeat-region extensions to the core tetrasaccharide linkage region structure. They have the following structures: deltaUA(beta1-3)GalNAc(beta1-4)GlcA(beta1-3)GalNAc(beta1-4)+ ++GlcA(beta1-3)Gal(beta1-3)Gal(beta1-4)Xyl-ol, deltaUA(beta1-3)GalNAc(beta1-4)GlcA(beta1-3)GalNAc6S(b eta1-4)GlcA(beta1-3)Gal(beta1-3)Gal(beta1-4)Xyl-ol, deltaUA(beta1-3)GalNAc6S(beta1-4)GlcA(beta1-3)GalNAc(b eta1-4)GlcA(beta1-3)Gal(beta1-3)Gal(beta1-4)Xyl-ol, deltaUA(beta1-3)GalNAc6S(beta1-4)GlcA(beta1-3)GalNA c6S(beta1-4)GlcA(beta1-3)Gal(beta1-3)Gal(beta1-4)Xyl-ol and deltaUA(beta1-3)GalNAc4S(beta1-4)GlcA(beta1-3)GalNA c6S(beta1-4)GlcA(beta1-3)Gal(beta1-3)Gal(beta1-4)Xyl-ol. They differ only in the nature of the sulphation of the GalNAc residues of the tetrasaccharide-repeat-region extension, which forms the first two disaccharides of the repeat region. No sulphation of any of the uronic acid residues has been identified and in one oligosaccharide neither of the GalNAc residues were sulphated. The majority of the linkage regions contained GalNAc residues which were fully 6-sulphated. However, in a significant amount, only one of the residues was 6-sulphated while the other was either unsulphated or 4-sulphated. There was no evidence either for sulphation of the linkage region galactose residues or for phosphorylation of the xylose residue, through which the chain is attached to the core protein.

Regioselective deacetylation of peracetylated monosaccharide derivatives by polyethylene glycol-modified lipase for the oligosaccharide synthesis

Lipase modified with polyethylene glycol became soluble and active in organic solvents, and catalyzed regioselective deacetylation of peracetylated monosaccharide derivatives in 1,1,1-trichloroethane. The deacetylation occurred only at the positions of C-4 and C-6 of the glycopyranoside ring. Especially, peracetylated methyl β-D-xylopyranoside and peracetylated L-serine-β-D-xylopyranoside were hydrolyzed only at the position of C-4. Subsequently, one of the resulting products, that is L-serine-2,3-di-O-acetyl-β-D-xylopyranoside, was coupled with galactose residue to obtain L-serine-4-O-(β-D-galactopyranosyl)-β-D-xylopyranoside, a model compound of the carbohydrate-protein linkage region of proteoglycans.

Structural variations in the glycosaminoglycan-protein linkage region of recombinant decorin expressed in Chinese hamster ovary cells.

Decorin is a small fibroblast proteoglycan consisting of a core protein and a single chondroitin/dermatan sulfate chain. The structure of the carbohydrate-protein linkage region of the recombinant decorin expressed in Chinese hamster ovary cells was investigated. The decorin was secreted in the culture medium and isolated by anion-exchange chromatography. The glycosaminoglycan chain was released from the decorin by beta-elimination using alkaline NaBH4, and then digested with chondroitinase ABC. These treatments resulted in a major and a few minor hexasaccharide alditols derived from the carbohydrate-protein linkage region. Their structures were analyzed by enzymatic digestion in conjunction with high-performance liquid chromatography. Two of these compounds have the conventional hexasaccharide core, deltaHexA alpha1-3GalNAc beta1-4GlcA beta1-3Gal beta1-3Gal beta1-4Xyl-ol. One is nonsulfated, and the other is monosulfated on C4 of the GalNAc residue. They represent 12% and 60% of the total linkage region, respectively. The other compound has the hexasaccharide alditol with an internal iduronic acid residue deltaHexA alpha1-3GalNAc(4-sulfate)beta1-4IdoA alpha1-3Gal beta1-3Gal beta1-4Xyl-ol, which was previously demonstrated in one of the five linkage hexasaccharide alditols isolated from dermatan sulfate proteoglycans of bovine aorta (Sugahara et al., J. Biol. Chem., 270, 7204-7212, 1995). The compound accounts for 11% of the total linkage region. These structural variations in the linkage hexasaccharide region of the decorin strikingly contrast to the uniformity demonstrated in the linkage hexasaccharide structure of human inter-alpha-trypsin inhibitor (Yamada et al., Glycobiology, 5, 335-341, 1995) and urinary trypsin inhibitor (Yamada et al., Eur. J. Biochem., 233, 687-693, 1995), both of which have a single chondroitin sulfate chain with a uniform linkage hexasaccharide structure, deltaHexA alpha1-3GalNAc(4-sulfate)beta1-4GlcA beta1-3Gal(4-sulfate)beta1-3Gal beta1-4Xyl, containing a 4-O-sulfated Gal residue.

Complete 1H NMR assignments of synthetic glycopeptides from the carbohydrate-protein linkage region of serglycins.

We present complete 1H NMR assignments for two synthetic glycopeptides representative of the carbohydrate-protein linkage region of serglycin proteoglycans. The peptides are: Ser(Galp-Xylp)-Gly-Ser-Gly-Ser(Galp-Xylp)-Gly and, Ser(Galp-Xylp)-Gly-Ser(Galp-Xylp)-Gly-Ser(Galp-Xylp)-G ly. A number of 2D NMR spectra together with a 3D NOESY-TOCSY spectrum were acquired at 600 MHz to complete the assignments of the glycopeptides dissolved in water with 40% trifluoroethanol. Preliminary analysis of the NMR data suggests folded structures for the glycopeptides.

A stereocontrolled synthetic approach to glycopeptides corresponding to the carbohydrate-protein linkage region of cell-surface proteoglycans

The glycopeptides 1 ( Gly{O-β- D- Xylp }- L-Ser-Gly- L-Glu ) and 2 ( Gly{O-[β- D- GlcpA-(1→3)-β- D- Galp-(1→3)-β- D- Galp]-(1→4)-β- D- Xylp}- L- Ser-Gly- L- Glu }- L- Ser-Gly- L- Glu) ), carrying the core structure of serine-linked cell-surface proteoglycans were synthesized in a stereocontrolled manner. The carbohydrate key imidate xylosyl donors 3 and glycotetraosyl donors 4 and 5, as well as a tetrapeptide glycosyl acceptor 6, were coupled in the crucial glycosylation step. In these reactions, the application of either trimethylsilyl trifluoromethanesulfonate (TMSOTf) or borontrifluoride etherate (BF 3-Et 2O) as catalysts proved to be highly efficient. The serine linked glycopeptides 34, 36 and 37 thus obtained yielded target compounds 1 and 2 on complete deprotection.

The uniform galactose 4-sulfate structure in the carbohydrate-protein linkage region of human urinary trypsin inhibitor.

The carbohydrate-protein linkage region of a chondroitin 4-sulfate chain attached to urinary trypsin inhibitor (UTI) was isolated from human urine and characterized structurally. The chondroitin 4-sulfate chain was released from UTI by beta-elimination using alkaline NaBH4 then digested with chondroitinase ABC. These treatments resulted in only a single hexasaccharide alditol derived from the carbohydrate-protein linkage region. Chemical and enzymic analyses and 600-MHz 1H-NMR spectroscopy revealed that the hexasaccharide alditol had the following structure: delta HexA alpha 1-3GalNAc(4-sulfate) beta 1-4GlcA beta 1- 3Gal(4-sulfate) beta 1-3Gal beta 1-4Xyl-ol, where delta HexA, GlcA and Xyl-ol represent 4-deoxy-alpha-L-threo-hex-4-enepyranosyluronic acid, D-glucuronic acid and D-xylitol, respectively. This structure contained the novel 4-sulfated Gal residue, which was first demonstrated in one of the three linkage hexasaccharide-serines isolated from chondroitin 4-sulfate of rat chondrosarcoma [Sugahara, K., Yamashina, I., de Waard, P., Van Halbeek, H. & Vliegenhart, J. F. G. (1988) J. Biol. Chem. 263, 10168-10174]. This disulfated structure was recently identified as the sole structural component in the linkage hexasaccharide alditol fraction isolated from inter-alpha-trypsin inhibitor (ITI) in human plasma [Yamada, S., Oyama, M., Kinugasa, H., Nakagawa, T., Kawasaki, T., Nagasawa, S., Khoo, K.-H., Morris, H.R., Dell, A. & Sugahara, K. (1995) Glycobiology 5, 335-341]. The structural uniformity in the linkage hexasaccharide structure of ITI and UTI is in marked contrast to the heterogeneity demonstrated in the linkage hexasaccharides isolated from cartilaginous chondroitin sulfate whose linkage regions are sometimes but not always phosphorylated on the Xyl residue or sulfated on the Gal residue(s). The uniform structure containing the novel 4-sulfated Gal residue in the linkage region of UTI and ITI may imply its significance in the biosynthetic mechanism of chondroitin sulfate.

Structure Determination of the Octa- and Decasaccharide Sequences Isolated from the Carbohydrate-Protein Linkage Region of Porcine Intestinal Heparin

Previously we isolated a tetrasaccharide-serine and a hexasaccharide-serine from the carbohydrate-protein linkage region of porcine intestinal heparin after digestion with a mixture of Flavobacterium heparinase and heparitinases I and II (Sugahara, K., Yamada, S., Yoshida, K., de Waard, P., and Vliegenthart, J.F.G. (1992) J. Biol. Chem. 267, 1528-1533). In this study four longer carbohydrate sequences (I-IV) attached to Ser or a dipeptide (Ser-Gly or Gly-Ser), which accounted for at least 18.2% of the total linkage region, were isolated from the same heparin preparation after digestion with heparinase only. IV was successfully isolated only after subsequent digestion with glycuronate-2-sulfatase. Their structures were determined by chemical and enzymatic analyses and 1H NMR spectroscopy and found to be the following octa- and decasaccharide sequences attached to Ser in a molar ratio of 1.1:2.3:1.0:1.3: delta HexA(2S)alpha 1-4GlcN(NS,6S)alpha 1-4GlcA beta 1-4GlcNAc alpha 1-4- GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser (I), delta HexA(2S)alpha 1- 4GlcN(NS,6S)alpha 1-4IdoA alpha 1-4GlcNAc alpha 1-4GlcA beta 1- 3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser (II), delta HexA(2S)alpha 1- 4GlcN(NS,6S)alpha 1- 4IdoA alpha 1-4GlcNAc alpha 1-4GlcA beta 1-4GlcNAc-alpha 1- 4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser (III), delta HexA alpha 1-4GlcN(NS,6S)alpha 1-4IdoA alpha 1-4GlcNAc(6S)alpha 1- 4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser (IV) (delta HexA, GlcA, IdoA, and GlcN represent 4,5-unsaturated hexuronic acid, D-glucuronic acid, L-iduronic acid, and D-glucosamine, whereas 2S, 6S, and NS stand for 2-sulfate, 6-sulfate, and N-sulfate, respectively). I and II contained 1 mol of Gly in addition to Ser. The four structures indicate that sulfation in heparin chains takes place on the monosaccharide residues located in closer vicinity to the core protein than found for heparan sulfate chains and that there exist at least several heparin subclass chains with different linkage region structures. The significance of the isolated structures is discussed in relation to the biological functions and the biosynthetic mechanisms of heparin.

Structural Studies on the Hexasaccharide Alditols Isolated from the Carbohydrate-Protein Linkage Region of Dermatan Sulfate Proteoglycans of Bovine Aorta: DEMONSTRATION OF IDURONIC ACID-CONTAINING COMPONENTS

Five major hexasaccharide alditols were isolated from the carbohydrate-protein linkage region of bovine aorta dermatan sulfate peptidoglycans after reductive beta-elimination and subsequent chondroitinase ABC digestion. These molecules account for at least 55.3% of the total linkage region. Their structures were analyzed by enzymatic digestion in conjunction with high performance liquid chromatography, electrospray ionization mass spectrometry, and 500-MHz one- and two-dimensional 1H NMR spectroscopy. Three of these compounds have the conventional hexasaccharide core; delta HexA alpha 1-3Gal-NAc beta 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl-ol. One is nonsulfated, and the other two are monosulfated on C6 or C4 of the GalNAc residue. They represent at least 6.3, 5.2, and 28.8% of the total linkage region, respectively. The other two compounds have the following hitherto unreported hexasaccharide core with an internal iduronic acid residue in common; delta HexA alpha 1-3GalNAc beta 1-4IdoA alpha 1-3Gal beta 1-3Gal beta 1-4Xyl-ol. One is monosulfated on C4 of the GalNAc, and the other is disulfated on C4 of the GalNAc and of the galactose residue substituted by the iduronic acid residue. These two compounds account for 35% of the five isolated hexasaccharide alditols and at least 4.3 and 10.7% of the total linkage region, respectively. The latter two structures form a striking contrast to the currently accepted conception that heparin, heparan sulfate, and chondroitin/dermatan sulfate share the common linkage tetrasaccharide core GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl. The biological significance of the isolated structures is discussed in relation to the biological functions and the biosynthetic mechanisms of dermatan sulfate.

The sulphated carbohydrate-protein linkage region isolated from chondroitin 4-sulphate chains of inter-alpha-trypsin inhibitor in human plasma.

Inter-alpha-trypsin inhibitor (ITI) in human plasma has a unique structural architecture composed of three polypeptide chains (H1, H2 and L chains), which are linked to each other through a chondroitin 4-sulphate chain. The structure of the carbohydrate-protein linkage region of the chondroitin 4-sulphate chain attached to the L chain was investigated. The peptide-chondroitin sulphate fraction was isolated by anion-exchange chromatography after exhaustive digestion with lysyl endopeptidase and then V8 protease. The chondroitin 4-sulphate chain was released from the peptides by beta-elimination using NaB3H4 and then digested with chondroitinase ABC. These treatments resulted in a single 3H-labelled hexasaccharide alditol fraction derived from the linkage region which had been associated with the L chain. Chemical and enzymatic analyses as well as fast-atom bombardment-mass spectrometry (FAB-MS) analysis revealed that the 3H-labelled hexasaccharide alditol had the following structure: delta HexA-alpha 1-3GalNAc(4-sulphate)beta 1-4GlcA beta 1-3Gal(4-sulphate)beta 1-3Gal beta 1-4Xyl-ol (where delta HexA is 4-deoxy-alpha-L-threo-hex-4-enepyranosyluronic acid and Xyl-ol is xylitol). The structure contained the novel 4-sulphated Gal residue, which was previously demonstrated in a linkage hexasaccharide isolated from chondroitin 4-sulphate of rat chondrosarcoma (Sugahara et al., J. Biol. Chem., 263, 10168-10174, 1988) and of whale cartilage (Sugahara et al., Eur. J. Biochem., 202, 805-811, 1991). The above disulphated hexasaccharide alditol was the only component detected in the linkage region fraction of the chondroitin 4-sulphate chain of ITI, which implies some biological significance of this novel structure.

Synthesis of sulfated and phosphorylated glycopeptides from the carbohydrate-protein linkage region of proteoglycans

The synthesis of the tetrasaccharide dipeptide β- d-Glc pA-(1 → 3)-β- d-Gal p4SO 3Na-(1 → 3)-β- d-Gal p-(1 → 4)-β- d-Xyl p-(1 → O)- l-Ser-Gly was achieved by coupling a suitably protected tetrasaccharide trichloroacetimidate, built up from the nonreducing end by the stepwise addition of monosaccharide units, to the protected dipeptide Z- l-Ser-Gly- OBn. Sulfation at O-4 of the second d-Gal unit and complete deprotection afforded the target molecule in high yield. Its phosphorylated analogue β- d-Glc pA-(1 → 3)-β- d-Gal p-(1 → 3)-β- d-Gal p-(1 → 4)-β- d-Xyl p2PO 3Na 2-(1 → O)- l-Ser-Gly was synthesized by coupling a protected trisaccharide trichloroacetimidate to the 2,3- O-isopropylidene derivative of Z-( d-Xyl-) l-Ser-Gly-OBn. Hydrolysis of the O-isopropylidene group, regioselective acetylation at O-3 of the O-Xyl unit, and phosphorylation at O-2 followed by complete deprotection gave the phosphoryltaed tetrasaccharide dipeptide in high yield. These structures are found in the carbohydrate-protein linkage region of several proteoglycans.

Structural studies on the oligosaccharides isolated from bovine kidney heparan sulphate and characterization of bacterial heparitinases used as substrates.

We prepared a series of oligosaccharides from commercial bovine kidney heparan sulphate after limited digestion with heparitinase I from Flavobacterium heparinum, and determined the structures of eight tetrasaccharides and a hexasaccharide by enzymatic analysis, fast atom bombardment mass spectrometry and 500 MHz 1H NMR spectroscopy. The tetrasaccharides share the common core structure delta 4,5HexA alpha 1-4GlcN alpha 1-4HexA1-4GlcN (where delta 4,5HexA is 4-deoxy-alpha-L-threo-hex-4-enopyranosyluronic acid and HexA is hexuronic acid), with zero, one or two sulphate groups. Seven of them contain non-sulphated glucuronic or iduronic acid, and the other, 2-O-sulphated iduronic acid at the internal position. Although they contain ordinary structures which should be widely distributed in the relatively low-sulphated region of heparan sulphate, five of the tetrasaccharides were isolated for the first time as discrete structures. The structure of the hexasaccharide was determined as delta 4,5HexA alpha 1-4GlcNAc alpha 1-4GlcA beta 1-3Gal beta 1-3Gal beta-1-4 Xyl and is derived from the carbohydrate-protein linkage region of the heparan sulphate chains. The hexasaccharide seems to have been released by the alkaline treatment used to prepare the heparan sulphate. The Gal residues were non-sulphated as are those in the porcine intestinal heparin chains, but in contrast to the sulphated Gal structures previously demonstrated in the carbohydrate-protein linkage region of chondroitin sulphate chains. These oligosaccharides were used to investigate the substrate specificity of heparitinases I and II from F. heparinum. The results revealed that heparitinase I cleaves hexosaminidic bonds linked to non-sulphated glucuronic or iduronic acid residues. The glucosaminidic linkage of the hexasaccharide was sensitive to heparitinase I, but resistant to heparitinase II, demonstrating the differential specificity of these enzymes towards the carbohydrate-protein linkage region.

Structural studies on the tri- and tetrasaccharides isolated from porcine intestinal heparin and characterization of heparinase/heparitinases using them as substrates.

We prepared a series of oligosaccharides from porcine intestinal heparin after extensive digestion with a mixture of Flavobacterium heparinase as well as heparitinases I and II. Previously, we reported the structures of the two glycoserines derived from the carbohydrate-protein linkage region [Sugahara et al., J. Biol. Chem., 267, 1528-1533 (1992)] and three tetrasaccharides derived from the antithrombin III-binding site [Yamada et al., J. Biol. Chem., 268, 4780-4787 (1993)]. In this study, we determined the structures of 10 other tetrasaccharides and a trisaccharide by enzymatic digestion, fast atom bombardment mass spectrometry and 500-MHz 1H NMR spectroscopy. These tetrasaccharides share the common disulphated structure, delta HexA alpha 1-4GlcN(N-sulphate)alpha 1-4IdoA(2-sulphate)alpha 1-4GlcN (where HexA is hexuronic acid and IdoA is L-iduronic acid), and their structural variations are based upon the positions of additional sulphate groups. Eight among the 10 have never been isolated as discrete structures. The structure of the trisaccharide is GlcN(N-sulphate)alpha 1-4IdoA(2-sulphate) alpha 1-4GlcN(N,6-disulphate) and is derived from the non-reducing terminus of heparin chains. This structure may represent the terminus of a biosynthetically formed native heparin chain or a newly formed non-reducing terminus exposed by a tissue endo-beta-glucuronidase which may be involved in the intracellular post-synthetic fragmentation of macromolecular heparin. The 11 structures characterized in the present study and 6 additional tetrasaccharides were used to investigate the substrate specificities of heparinase, as well as heparitinases I and II. The results indicate that modification of the adjacent glucosamine on the reducing side of the disaccharide cleavage site influences the enzymatic action of the lyases, whereas the adjacent uronic acid on the non-reducing side is not recognized by these enzymes.

Total synthesis of the carbohydrate-protein linkage region common to several mammalian proteoglycans

A stereocontrolled synthesis of β-d-GlcpA-(1 → 3)-β-d-Galp-(1 → 3)-β-d-Galp-(1 → 4)-β-d-Xylp-(1 → O)-l-Ser-Gly, the common glycopeptide sequence of the carbohydrate-protein linkage region of most mammalian proteoglycans, was achieved by use of O-[2-(trimethylsilyl)ethyl 2,3,4-tri-O-benzoyl-β-d-glucopyranosyluronate]-(1 → 3)-O-(2,4,6-tri-O-benzoyl-β-d-galactopyranosyl)-(1 → 3)-O-(2,4,6-tri-O-benzoyl-β-d-galactopyranosyl)-(1 → 4)-2,3-di-O-benzoyl-α,β-d-xylopyranosyl trichloroacetimidate as the key intermediate. Condensation of this glycosyl donor with suitably protected l-seryl-glycine dipeptide segments, and peptide chain elongation, allowed the construction in high yield of complex structures of this linkage region.

Structural studies on sulfated oligosaccharides derived from the carbohydrate-protein linkage region of chondroitin 6-sulfate proteoglycans of shark cartilage. II. Seven compounds containing 2 or 3 sulfate residues.

Shark cartilage proteoglycans bear predominantly chondroitin 6-sulfate. After exhaustive protease digestion, reductive beta-elimination and subsequent chondroitinase ABC digestion, 13 hexasaccharide alditols were obtained from the carbohydrate-protein linkage region and six of them contain 0 or 1 sulfate and/or 1 phosphate residue (Sugahara, K., Ohi, Y., Harada, T., de Waard, P., and Vliegenthart, J. F. G. (1992) J. Biol. Chem. 267, 6027-6035). The other seven compounds, which represent approximately 60% of the isolated linkage hexasaccharides, were analyzed by chondroitinase ACII digestion in conjunction with high performance liquid chromatography and by 500-MHz one- and two dimensional 1H NMR spectroscopy. All seven compounds have the following conventional structure in common. [formula: see text] Two disulfated compounds have an O-sulfate on C-6 of the Gal-2 residue attached to xylitol in combination with an O-sulfate on C-4 or on C-6 of the GalNAc residue. The third disulfated compound has O-sulfate on C-6 of Gal-2, and also on C-6 of Gal-3. Two of the trisulfated compounds also have O-sulfate on C-6 of both Gal-2 and Gal-3 with in addition sulfate on C-6 or C-4 of GalNAc. The other two trisulfated compounds have O-sulfate on C-6 of Gal-2 and on C-4 of Gal-3 in conjunction with sulfate on C-6 or C-4 of GalNAc.

Structural studies on sulfated oligosaccharides derived from the carbohydrate-protein linkage region of chondroitin 6-sulfate proteoglycans of shark cartilage. I. Six compounds containing 0 or 1 sulfate and/or phosphate residues.

Shark cartilage proteoglycans bear predominantly chondroitin 6-sulfate. After exhaustive protease digestion, reductive beta-elimination, and subsequent chondroitinase ABC digestion, 13 hexasaccharide alditols, which are nonsulfated, sulfated, and/or phosphorylated, were obtained from the carbohydrate-protein linkage region. Six compounds, containing 0 or 1 sulfate and/or phosphate residue, represent approximately 40% of the isolated linkage hexasaccharide alditols. They were analyzed by chondroitinase ACII or alkaline phosphatase digestion in conjunction with high performance liquid chromatography, and by 500 MHz one- and two-dimensional 1H NMR spectroscopy. All six compounds have the conventional structure in common. Delta 4,5-GlcA beta 1-3GalNAc beta 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl-ol One compound has no sulfate nor phosphate. Two of the monosulfated compounds have a O-sulfate on C-6 or on C-4 of the GalNAc residue. The third monosulfated compound has a novel O-sulfate on C-6 of the Gal residue attached to xylitol. The two phosphorylated compounds have O-phosphate on C-2 of Xyl-ol, and one of them has in addition sulfate on C-6 of GalNAc.