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

Polydispersity in sulfation profile of oligosaccharide alditols isolated from the protein-linkage region and the repeating disaccharide region of chondroitin 4-sulfate of bovine nasal septal cartilage

Proteoglycans of bovine nasal septal cartilage bear predominantly chondroitin 4-sulfate. After exhaustive chondroitinase ABC digestion of a chondromucoprotein preparation rich in proteoglycans and subsequent reductive beta-elimination, five hexasaccharide alditols were isolated from the glycosaminoglycan-protein linkage region. They were analyzed by enzymatic digestion in conjunction with HPLC and by one-dimensional and two-dimensional 1H-NMR spectroscopy. They share the conventional core saccharide structure delta 4.5HexA alpha 1-3GalNAc beta 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl-ol (where delta 4.5HexA is 4,5-unsaturated hexuronic acid), but have different sulfation profiles. One compound (I) does not contain sulfate. Two of the three monosulfated compounds (II and III) have an O-sulfate group at either C6 or at C4 of the GalNAc residue. The other monosulfated compound (IV) is hitherto unreported and has a O-sulfate at C4 of the Gal residue preceding the GlcA residue, whereas the GalNAc is not sulfated. The disulfated compound (V) has sulfate groups at C4 of both the Gal residue preceding GlcA and the GalNAc residue. The molar ratio of compounds I-V is 38.3:5.9:43.0:1.6:11.2. The structural heterogeneity of these hexasaccharide alditols reflects the polydispersity in the linkage region of the chondroitin sulfate chains. In addition, two trisaccharide and two tetrasaccharide alditols derived from the repeating disaccharide region of the chondroitin sulfate chains were also isolated. Their structures were unambiguously determined by enzymatic analysis and by 1H-NMR spectroscopy as delta 4.5HexA alpha 1-3GalNAc(4-O- or 6-O-sulfate)beta 1-4GlcA-ol and delta 4.5HexA alpha 1-3GalNAc(4-O- or 6-O-sulfate) beta 1-4GlcA beta 1-3GalNAc(4-O-sulfate)-ol, respectively.

Structural analysis of unsaturated hexasaccharides isolated from shark cartilage chondroitin sulfate D that are substrates for the exolytic action of chondroitin ABC lyase

The enzymatic action of highly purified chondroitin ABC lyase from Proteus vulgaris is dependent on the size of the substrate, and the enzyme does not cleave tetrasaccharides, irrespective of their sulfation profiles [Sugahara, K., Shigeno, K., Masuda, M., Fujii, N., Kurosaka, A. & Takeda, K. (1994) Carbohydr. Res. 255, 145-163]. To characterize the enzyme action in more detail, we isolated nine sulfated hexasaccharides from commercial shark cartilage chondroitin sulfate D, after partial digestion with highly purified chondroitin ABC lyase, by means of gel chromatography and HPLC on an amine-bound silica column. Structural analysis by 500-MHz H-NMR spectroscopy, and enzymatic digestion in conjunction with HPLC, demonstrated that these hexasaccharides, with the common core saccharide structure delta 4 HexA (alpha 1-3)GalNAc(beta 1-4)GlcA(beta 1-3)GalNAc(beta 1-4) GlcA(beta 1-3)GalNAc(where delta 4 HexA and GlcA represent 4-deoxy-alpha-L-threo-hex-4-enepyranosyluronic acid and glucuronic acid, respectively) bear three or four sulfate groups in different combinations. In the hexasaccharides, the D, disaccharide unit GlcA2-SO3 (beta 1-3) GalNAc4SO(3-) which is characteristic of chondroitin sulfate D, was arranged on the reducing side of the A disaccharide unit GlcA(beta 1-3)GalNAc4SO(3)-, and thus formed an A-D tetrasaccharide sequence GlcA(beta 1-3)GalNAc4SO(3)-(beta 1-4)GlcA2SO(3)-(beta 1-3) GalNAc6SO(3)-. Analysis of the degradation products of these hexasaccharides with highly purified chondroitin ABC lyase indicated that the enzyme preferentially acted on the unsaturated hexasaccharides in an exolytic fashion and removed an unsaturated disaccharide unit from the non-reducing termini, irrespective of the sulfation profiles of the hexasaccharides.

Specificity studies of bacterial sulfatases by means of structurally defined sulfated oligosaccharides isolated from shark cartilage chondroitin sulfate D

Chondro-4-sulfatase and chondro-6-sulfatase from Proteus vulgaris and delta-hexuronate-2-sulfatase from Flavobacterium heparinum are potentially useful tools for structural studies of chondroitin sulfate and dermatan sulfate. Their substrate specificities were investigated with various structurally defined, sulfated hexasaccharides isolated from chondroitin sulfate as described in the accompanying report [Sugahara, K., Nadanaka, S., Takeda, K. & Kojima, T. (1996) Eur. J. Biochem. 239, 871-880]. The results indicated that delta-hexuronate-2-sulfatase released an ester sulfate from the C2 position of the delta-hexuronate residue located at the non-reducing terminus, while chondro-6-sulfatase removed an ester sulfate from the C6 position of the GalNAc residue at the reducing end of the hexasaccharides. Chondro-4-sulfatase acted preferentially on an ester sulfate on the C4 position of the GalNAc residue at the reducing end under mild incubation conditions, but also released a sulfate group under harsh conditions from the C4 position of the GalNAc residue at the internal positions of the hexasaccharide chains, unless the GalNAc residue had another ester sulfate on its C6 position. The results demonstrated the usefulness of the sulfatases as tools for the structural characterization of chondroitin sulfate oligosaccharides.

Preparation of a series of sulfated tetrasaccharides from shark cartilage chondroitin sulfate D using testicular hyaluronidase and structure determination by 500 MHz 1H NMR spectroscopy

Six tetrasaccharide fractions were isolated from shark cartilage chondroitin sulfate D by gel filtration chromatography followed by HPLC on an amine-bound silica column after exhaustive digestion with testicular hyaluronidase. Their structures were determined unambiguously by one- and two-dimensional 500 MHz 1H NMR spectroscopy in conjunction with HPLC analysis of chondroitinase AC-II digests of the tetrasaccharides. One fraction was found to contain two tetrasaccharide components. All of the seven tetrasaccharides shared the common core structure GlcA beta 1-3GalNAc beta 1-4GLcA beta 1-3GalNAc with various sulfation profiles. Four were disulfated comprising of two monosulfated disaccharide units GLcA beta 1-3GalNAc(4-sulfate) and/or GlcA beta 1-3GalNAc(6-sulfate), whereas the other three were hitherto unreported trisulfated tetrasaccharides containing a disulfated disaccharide unit GlcA(2-sulfate)beta 1-3GalNAc(6-sulfate) and a monosulfated disaccharide unit GlcA beta 1-3GalNac(4- or 6-sulfate). These sulfated tetrasaccharides were demonstrated to serve as appropriate acceptor substrates for serum alpha-N-acetylgalactosaminyltransferase, indicating their usefulness as authentic oligosaccharide substrates or probes for the glycobiology of sulfated glycosaminoglycans.

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.

N-acetylgalactosamine (GalNAc) transfer to the common carbohydrate-protein linkage region of sulfated glycosaminoglycans. Identification of UDP-GalNAc:chondro-oligosaccharide alpha-N-acetylgalactosaminyltransferase in fetal bovine serum

During the course of a study of elucidate the role of modification of the common polysaccharide-protein linkage structure, GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser, in biosynthetic sorting mechanisms of the different sulfated glycosaminoglycan chains, a novel N-acetylgalactosamine (GalNAc) transferase was discovered in fetal bovine serum. The enzyme catalyzed the transfer of [3H]GalNAc from UDP-[3H]GalNAc to linkage tetrasaccharide and hexasaccharide serines synthesized chemically and to various regular oligosaccharides containing terminal D-glucuronic acid (GlcA), which were prepared from chondroitin and chondroitin sulfate using testicular hyaluronidase digestion. The labeled products obtained with the linkage tetra- and hexasaccharide serines and with the tetrasaccharide (GlcA beta 1-3GalNAc)2 were resistant to digestion with chondroitinase AC-II and beta-N-acetylhexosaminidase but sensitive to alpha-N-acetylgalactosaminidase digestion, indicating that the enzyme is an alpha-N-acetylgalactosaminyltransferase. This finding is in contrast to that of Rohrmann et al. (Rohrmann, K., Niemann, R., and Buddecke, E. (1985) Eur. J. Biochem., 148, 463-469), who reported that a corresponding product was susceptible to digestion with beta-N-acetylhexosaminidase. The presence of a sulfate group at C4 of the penultimate GalNAc or Gal units markedly inhibited the transfer of GalNAc to the terminal GlcA, while a sulfate group at C6 of the GalNAc had little effect on the transfer. Moreover, a slight but significant transfer of [3H]GalNAc was observed to an oligosaccharide containing terminal 2-O-sulfated GlcA as acceptor, whereas no incorporation was detected into oligosaccharides containing terminal unsaturated or 3-O-sulfated GlcA units. These results suggest that this novel serum enzyme is a UDP-GalNAc:chondro-oligosaccharide alpha 1-3- or 1-4-N-acetylgalactosaminyltransferase. The possibility of involvement of this enzyme in glycosaminoglycan biosynthesis is discussed.