Differentiation of two variants of type-AB GM2-gangliosidosis using chromogenic substrates.

Two variants of type-ABGM2-gangliosidosis can be distinguished by using p-nitrophenyl-6-sulfo-2-acetamido-2-deoxy-beta-D-glucopyranoside (PNP-GlcNAc-6-SO4) as substrate. One of the variants is caused by a deficiency of the activator for the hydrolysis of GM2-ganglioside. The beta-hexosaminidase A from this variant has a normal activity toward both PNP-GlcNAc and PNP-GlcNAc-6-SO4. A second variant caused by a defect in the enzyme, beta-hexosaminidase A, exhibits severely attenuated activity toward PNP-GlcNAc-6-SO4 but normal activity toward PNP-GlcNAc.     

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.     

Sialylation in vitro of purified human liver beta-D-N-acetylhexosaminidase

In order to study structure-function relationships of lysosomal enzymes, human liver beta-N-acetylhexosaminidase (2-acetamido-2-deoxy-beta-D-hexoside acetamidodeoxyhexohydrolase, EC 3.2.1.52) has been purified by an extraction/affinity chromatography/ion-exchange procedure. The isoenzymes A and B, native as well as neuraminidase-treated, were incubated with a partially purified preparation of bovine colostrum sialyltransferase (CMP-N-acetylneuraminate: D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1). Native beta-N-acetylhexosaminidases were found to be poor acceptors for the sialyltransferase used. However, incorporation of sialic acid into neuraminidase-treated beta-N-acetylhexosaminidase A and B amounted to a 58 to 72% saturation of the theoretical acceptor sites, respectively. The acceptor specificity of the sialyltransferase suggests that Gal beta(1 leads to 4)-GlcNAc units may be present on at least part of the beta-N-acetylhexosaminidase A and B molecules. However, oligomannosidic-type chains may also occur on the lysosomal enzyme, as shown by sugar composition of the enzyme. The presence and/or amount of sialic acid residues does not appear to affect the kinetic properties of beta-N-acetylhexosaminidase A and B towards 4-methylumbelliferyl glycoside substrate.     

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.     

Identification and characterization of a sulfoglycosidase from Bifidobacterium bifidum implicated in mucin glycan utilization

Human gut symbiont bifidobacteria possess carbohydrate-degrading enzymes that act on the O-linked glycans of intestinal mucins to utilize those carbohydrates as carbon sources. However, our knowledge about mucin type O-glycan degradation by bifidobacteria remains fragmentary, especially regarding how they decompose sulfated glycans, which are abundantly found in mucin sugar-chains. Here, we examined the abilities of several Bifidobacterium strains to degrade a sulfated glycan substrate and identified a 6-sulfo-β-d-N-acetylglucosaminidase, also termed sulfoglycosidase, encoded by bbhII from Bifidobacterium bifidum JCM 7004. A recombinant BbhII protein showed a substrate preference toward 6-sulfated and 3,4-disulfated N-acetylglucosamines over non-sulfated and 3-sulfated N-acetylglucosamines. The purified BbhII directly released 6-sulfated N-acetylglucosamine from porcine gastric mucin and the expression of bbhII was moderately induced in the presence of mucin. This de-capping activity may promote utilization of sulfated glycans of mucin by other bacteria including bifidobacteria, thereby establishing the symbiotic relationship between human and gut microbes.     

Enzymatic glycosylation using 6-O-acylated sugar donors and acceptors: beta-N-acetylhexosaminidase-catalysed synthesis of 6-O,N,N'-triacetylchitobiose and 6'-O,N,N'-triacetylchitobiose

p-Nitrophenyl 6-O-acetyl-2-acetamido-2-deoxy-beta-D-glucopyranoside (5a) was used as the glycosyl donor in a beta-N-acetylhexosaminidase-catalysed (from Penicillium brasilianum) glycosylation of GlcNAc yielding 6'-O,N,N'-triacetylchitobiose (6), while 6-O-acetyl-2-acetamido-2-deoxy-beta-D-glucopyranose (3a) served as a selectively protected acceptor in a transglycosylation reaction catalysed by the same enzyme to yield 6-O,N,N'-triacetylchitobiose (4).     

Structural analysis of N-linked oligosaccharides from glycoproteins secreted by Dictyostelium discoideum. Identification of mannose 6-sulfate

The N-linked oligosaccharides found on the lysosomal enzymes from Dictyostelium discoideum are highly sulfated and contain methylphosphomannosyl residues (Gabel, C. A., Costello, C. E., Reinhold, V. N., Kurtz, L., and Kornfeld, S. (1984) J. Biol. Chem. 259, 13762-13769). Here we report studies done on the structure of N-linked oligosaccharides found on proteins secreted during growth, a major portion of which are lysosomal enzymes. Cells were metabolically labeled with [2-3H]Man and 35SO4 and a portion of the oligosaccharides were released by a sequential digestion with endoglycosidase H followed by endoglycosidase/peptide N-glycosidase F preparations. The oligosaccharides were separated by anion exchange high performance liquid chromatography into fractions containing from one up to six negative charges. Some of the oligosaccharides contained only sulfate esters or phosphodiesters, but most contained both. Less than 2% of the oligosaccharides contained a phosphomonoester or an acid-sensitive phosphodiester typical of the mammalian lysosomal enzymes. A combination of acid and base hydrolysis suggested that most of the sulfate esters were linked to primary hydroxyl groups. The presence of Man-6-SO4 was demonstrated by the appearance of 3,6-anhydromannose in acid hydrolysates of base-treated, reduced oligosaccharides. These residues were not detected in acid hydrolysates without prior base treatment or in oligosaccharides first treated by solvolysis to remove sulfate esters. Based on high performance liquid chromatography quantitation of percentage of 3H label found in 3,6-anhydromannose, it is likely that Man-6-SO4 accounts for the majority of the sulfated sugars in the oligosaccharides released from the secreted glycoproteins.     

Separation of N-acetyl-beta-hexosaminidase isoenzymes. Methological note

We examined the activity of total N-acetyl-beta-hexosaminidase and of its isoenzyme forms, that represent different stages of the maturation of the lysosomal hydrolase. In both methods the enzyme catalyzes the separation of 4-methylumbelliferone, a fluorescent substance, from 4-methylumelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranoside. We used Leaback's method for the fluorimetric assay of total enzyme, and Ellis's DEAE-cellulose microcolum chromatography for the assay of its components. We obtained a clear separation of each fraction. We will apply these methods in our further studies of children with renal damage, because hexosaminidase seems to be one of the most sensitive markers of tubular damage.     

Synthesis of spacer-equipped phosphorylated di-, tri- and tetrasaccharide fragments of the O-specific polysaccharide of Vibrio cholerae O139

The synthesis of oligosaccharide fragments of the O-specific polysaccharide of Vibrio cholerae O139 containing a 4,6-cyclic phosphate galactose residue linked to GlcNAc is described. 8-Azido-3,6-dioxaoctyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl-(1-->3)-2-acetamido-4,6-O-benzylidene-2-deoxy-beta-D-glucopyranoside, obtained by condensation of 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide and 8-azido-3,6-dioxaoctyl 2-acetamido-4,6-O-benzylidene-2-deoxy-beta-D-glucopyranoside, was converted to 8-azido-3,6-dioxaoctyl 3-O-benzyl-beta-D-galactopyranosyl-(1-->3)-2-acetamido-6-O-benzyl-2-deoxy-beta-D-glucopyranoside (6) by reductive opening of the acetal, followed by deacetylation and selective benzylation. Phosphorylation of 6 furnished two isomeric 4,6-cyclic 2,2,2-trichloroethyl phosphates. Glycosylation of the (S)-phosphate with 2,4-di-O-benzyl-3,6-dideoxy-alpha-L-xylo-hexopyranosyl bromide under halide-assisted conditions gave the desired tetrasaccharide, together with a trisaccharide. Global deprotection and reduction of the azide to an amine was effected by catalytic hydrogenation/hydrogenolysis to give the deprotected tetrasaccharide, which is functionalized for conjugation.     

Glycoside hydrolase family 89 alpha-N-acetylglucosaminidase from Clostridium perfringens specifically acts on GlcNAc alpha1,4Gal beta1R at the non-reducing terminus of O-glycans in gastric mucin

In mammals, α-linked GlcNAc is primarily found in heparan sulfate/heparin and gastric gland mucous cell type mucin. α-N-acetylglucosaminidases (αGNases) belonging to glycoside hydrolase family 89 are widely distributed from bacteria to higher eukaryotes. Human lysosomal αGNase is well known to degrade heparin and heparan sulfate. Here, we reveal the substrate specificity of αGNase (AgnC) from Clostridium perfringens strain 13, a bacterial homolog of human αGNase, by chemically synthesizing a series of disaccharide substrates containing α-linked GlcNAc. AgnC was found to release GlcNAc from GlcNAcα1,4Galβ1pMP and GlcNAcα1pNP substrates (where pMP and pNP represent p-methoxyphenyl and p-nitrophenyl, respectively). AgnC also released GlcNAc from porcine gastric mucin and cell surface mucin. Because AgnC showed no activity against any of the GlcNAcα1,2Galβ1pMP, GlcNAcα1,3Galβ1pMP, GlcNAcα1,6Galβ1pMP, and GlcNAcα1,4GlcAβ1pMP substrates, this enzyme may represent a specific glycosidase required for degrading α-GlcNAc-capped O-glycans of the class III mucin secreted from the stomach and duodenum. Deletion of the C-terminal region containing several carbohydrate-binding module 32 (CBM32) domains significantly reduced the activity for porcine gastric mucin; however, activity against GlcNAcα1,4Galβ1pMP was markedly enhanced. Dot blot and ELISA analyses revealed that the deletion construct containing the C-terminal CBM-C2 to CBM-C6 domains binds strongly to porcine gastric mucin. Consequently, tandem CBM32 domains located near the C terminus of AgnC should function by increasing the affinity for branched or clustered α-GlcNAc-containing glycans. The agnC gene-disrupted strain showed significantly reduced growth on the class III mucin-containing medium compared with the wild type strain, suggesting that AgnC might have an important role in dominant growth in intestines.     

A sulfatase specific for glucuronic acid 2-sulfate residues in glycosaminoglycans

Although 2-O-sulfated L-iduronic acid (IdoA) residues have been known to occur in heparin, 2-O-sulfated D-glucuronic acid (GlcA) residues have been reported only recently (Bienkowski, M. J., and Conrad, H. E. (1985) J. Biol. Chem. 250, 356-365). Disaccharides prepared by cleavage of heparin and N-deacetylated chondroitin 6-sulfate with nitrous acid were used to demonstrate a new sulfatase that catalyzed the removal of the 2-O-sulfate substituents from GlcA but not IdoA residues. The deamination products were labeled by NaB3H4 reduction to give disaccharides from heparin and chondroitin sulfate which had reducing terminal 2,5-anhydro-D-mannitol ([3H]AManR) and 2,5-anhydro-D-talitol ([3H]ATalR) residues, respectively. IdoA(2-SO4)-[3H]AManR(6-SO4) from heparin and GlcA(2-SO4)-[3H]ATalR(6-SO4) from chondroitin sulfate were purified for use as substrates. GlcA(2-SO4)-[3H]AManR(6-SO4) was prepared by epimerization of IdoA(2-SO4)-[3H]AManR(6-SO4) with hydrazine at 100 degrees C. Lysosomal enzyme preparations from chick embryo chondrocytes and from two normal human fibroblast cell lines catalyzed the removal of the 2-O-SO4 substituent from the uronic acid residues of IdoA(2-SO4)-[3H]AManR(6-SO4), GlcA(2-SO4)-[3H] AManR(6-SO4), and GlcA(2-SO4)-[3H]ATalR(6-SO4). In contrast, a lysosomal enzyme preparation from a human fibroblast cell line deficient in idurono-2-sulfatase (Hunter's-syndrome), which had no activity on the IdoA(2-SO4)-[3H]AManR(6-SO4), converted GlcA(2-SO4)-[3H]AManR(6-SO4) to a mixture of GlcA-[3H] AManR(6-SO4) and [3H]AManR(6-SO4). This enzyme also converted GlcA(2-SO4)-[3H]ATalR(6-SO4) to a mixture of GlcA-[3H]ATalR(6-SO4) and [3H]ATalR(6-SO4). Digestion of both GlcA(2-SO4)-[3H]AManR(6-SO4) and GlcA(2-SO4)-[3H]ATalR(6-SO4) was inhibited by 35SO2-4 and was arrested at the monosulfated disaccharide stage by 1,4-saccharolactone. The glucurono-2-sulfatase exhibited a pH optimum of 4. The results indicate that there exists a separate sulfatase for the removal of sulfate substituents from C-2 of GlcA residues in glycosaminoglycans.     

Synthesis and conformational analysis of the repeating units of bacterial spore peptidoglycan

Deprotection of the fully blocked disacharide allyl O-(2-amino-4,6-O-benzylidene-3-O-[(R)-1-carboxyethyl]-2-deoxy-beta-D-glucopyranosyl-1',2-lactam)-(1-->4)-2-acetamido-3,6-di-O-benzyl-2-deoxy-beta-D-glucopyranoside by selective de-O-allylation and parallel removal of the benzylidene and O-benzyl groups is described. The resulting beta-muramyl lactam-(1-->4)-GlcNAc disaccharide is characterised as the per-O-acetylated derivative by 1H and 13C NMR spectroscopy and X-ray structure analysis. Conformational analysis about glycosidic bond of repeating units of bacterial spore cortex is based on experimental data and molecular modelling.     

Synthesis of sulfated phenyl 2-acetamido-2-deoxy-D-galactopyranosides. 4-O-Sulfated phenyl 2-acetamido-2-deoxy-beta-D-galactopyranoside is a competitive acceptor that decreases sulfation of chondroitin sulfate by N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase

We have previously cloned N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST), which transfers sulfate from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the C-6 hydroxyl group of the GalNAc 4-sulfate residue of chondroitin sulfate A and forms chondroitin sulfate E containing GlcA-GalNAc(4,6-SO(4)) repeating units. To investigate the function of chondroitin sulfate E, the development of specific inhibitors of GalNAc4S-6ST is important. Because GalNAc4S-6ST requires a sulfate group attached to the C-4 hydroxyl group of the GalNAc residue as the acceptor, the sulfated GalNAc residue is expected to interact with GalNAc4S-6ST and affect its activity. In this study, we synthesized phenyl alpha- or -beta-2-acetamido-2-deoxy-beta-D-galactopyranosides containing a sulfate group at the C-3, C-4, or C-6 hydroxyl groups and examined their inhibitory activity against recombinant GalNAc4S-6ST. We found that phenyl beta-GalNAc(4SO(4)) inhibits GalNAc4S-6ST competitively and also serves as an acceptor. The sulfated product derived from phenyl beta-GalNAc(4SO(4)) was identical to phenyl beta-GalNAc(4,6-SO(4)). These observations indicate that derivatives of beta-D-GalNAc(4SO(4)) are possible specific inhibitors of GalNAc4S-6ST.     

Synthesis of p-nitrophenyl 2-acetamido-2-deoxy-O-beta-D-galactopyranosyl-beta-D-glucopyranosides.

Reaction of p-nitrophenyl 2-acetamido-2-deoxy-4,6-O-(p-methoxybenzylidene)-beta-D-glucopyranoside (2) with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide (3) under the usual conditions, followed by removal of the p-methoxybenzylidene group and O-deacylation, produced crystalline p-nitrophenyl 2-acetamido-2-deoxy-3-O-beta-D-galactopyranosyl-beta-D-glucopyranoside (6). Starting from p-nitrophenyl 2-acetamido 3,4-di-O-acetyl-2-deoxy-beta-D-glucopyranoside, the synthesis of p-nitrophenyl 2-acetamido-2-deoxy-6-O-beta-D-galactopyranosyl-beta-D-glucopyranoside was also accomplished.     

Chondroitin SO4 catabolism in chick embryo chondrocytes

An enzyme preparation from cultured chick embryo vertebral chondrocytes attacks chondroitin SO4 oligosaccharides from the nonreducing terminal in a recycling pathway involving the sequential action of a beta-glucuronidase, a 4- or a 6-sulfatase, and a beta-N-acetylgalactosaminidase. The sequence is blocked by saccharo-1,4-lactone, an inhibitor of the beta-glucuronidase, or by 2-acetamido-2-deoxy-D-galactonolactone, an inhibitor of the beta-N-acetylgalactosaminidase. The level of 4-sulfatase activity is low relative to the other activities and limits the rate of catabolism of hybrid oligosaccharide structures containing both 6-sulfated galactosamine residues and 4-sulfated galactosamine residues. This results in the accumulation of shortened oligosaccharides, most of which have galactosamine-4-SO4 residues at their nonreducing terminals. In the presence of the lactone inhibitors, polymeric chondroitin SO4 is broken down by the enzyme preparation to oligosaccharides which are 10 to 15 monosaccharides long, indicating that degradation of chondroitin SO4 chains is initiated by an endoglycosidase which generates oligosaccharide substrates for the recycling exoglycosidase system.     

Mannose 6-sulfate is present in the N-linked oligosaccharides of lysosomal enzymes of Dictyostelium

The major N-linked, anionic oligosaccharide found on several lysosomal enzymes of Dictyostelium discoideum contains five charges, composed of three sulfate esters and two residues of Man-6-P in phosphodiester linkage. Most of the SO4 was found as Man-6-SO4. This novel sulfated sugar was detected and quantitated by measuring the appearance of 3,6-anhydromannitol following acid hydrolysis and reduction of base-treated, reduced oligosaccharides. If SO4 is removed by solvolysis prior to the base treatment, the anhydrosugar is not formed, indicating that its presence is not an artifact of the procedure. That these oligosaccharides are derived from standard high-mannose-type oligosaccharides indicates that only one or, at most, two Man residues are unsubstituted at the 6-position.     

Characterization of a thyroid sulfotransferase responsible for the 3-O-sulfation of terminal beta-D-galactosyl residues in N-linked carbohydrate units

Calf thyroid microsomes were found to contain an enzyme which catalyzes the transfer of sulfate from 3'-phosphoadenosine 5'-phospho[35S]sulfate (PAPS) to C-3 of terminal galactose residues in beta 1----4 linkage to GlcNAc. This sulfotransferase is believed to be involved in the biosynthesis of the recently described Gal(3-SO4) capping groups present in the N-linked oligosaccharides of thyroglobulin (Spiro, R.G., and Bhoyroo, V. D. (1988) J. Biol. Chem. 263, 14351-14358). Assays with various native and modified glycopeptides indicated that the enzyme acted optimally on complex-type carbohydrate units in which beta-linked Gal has been uncovered by desulfation or brought into a terminal position by removal of sialyl and/or alpha-galactosyl residues. With fetuin asialoglycopeptides as acceptors (Km = 0.1 mM) the transfer of sulfate from PAPS (Km = 6.3 microM) had a pH optimum of approximately 7.0, required Mn2+ ions (10-50 mM) and was markedly stimulated by Triton X-100 (0.1%) and ATP (2 mM). The same enzyme apparently sulfated free N-acetyllactosamine (LacNAc; Km = 0.69 mM) and its ethyl glycoside, indicating that it had no absolute requirement for a peptide recognition site. Studies with a number of disaccharides related to LacNAc provided information relating to the specifying role of the beta 1----4 galactosyl linkage and the configuration at C-2 of the sugar to which it is attached. Hydrazine-nitrous acid-NaBH4 treatment of the 35S-labeled products from sulfotransferase action on asialoglycopeptides as well as on the ethyl glycoside of LacNAc yielded the same disaccharide, Gal(3-SO4) beta 1----4 anhydromannitol, as is obtained from a similar treatment of thyroglobulin. Subcellular distribution studies indicated that the PAPS:galactose 3-O-sulfotransferase is located in the Golgi compartment which is consistent with the late occurrence of the requisite beta-galactosylation step. It is proposed that in certain tissues the ultimate nature of the capping groups attached to glycoproteins containing terminal Gal beta 1----4GlcNAc sequences could be the result of a competition between this 3-O-sulfotransferase and sialyl- and/or alpha-galactosyltransferases.     

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.     

Chemoenzymatic synthesis of the sialyl-alpha-(2-->3')-lactosamine trisaccharide with a 3-aminopropyl group as a spacer at the reducing end

The trisaccharide, 3-aminopropyl 5-acetamido-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylonic acid-(2-->3)-beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-beta-D-glucopyranoside has been synthesized chemoenzymatically for the first time. First, the acceptor, 3-aminopropyl beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-beta-D-glucopyranoside was synthesized in a conventional chemical manner, and then it was coupled with CMP-sialic acid using alpha-(2-->3)-(N)-sialyltransferase to afford the desired trisaccharide by an enzymatically stereocontrolled manner.     

Characterization of novel sequences containing 3-O-sulfated glucosamine in glomerular basement membrane heparan sulfate and localization of sulfated disaccharides to a peripheral domain

Fragmentation of the heparan sulfate chains from bovine glomerular basement membrane (GBM) by hydrazine/nitrous acid treatment followed by NaB3H4-reduction yielded a mixture of six sulfated disaccharides containing D-glucuronic (GlcUA) or L-iduronic acid (IdUA) and terminating in 2,5-anhydro[3H]mannitol (AnManH2), in addition to the nonsulfated component GlcUA beta 1----4AnManH2. Among these products two novel disaccharide units were identified as IdUA alpha 1----4AnManH2(3-SO4) and IdUA(2-SO4)alpha 1----4AnManH2(3-SO4); these accounted for 22% of the total sulfated species indicating that there are 2-3 residues of 3-O-sulfated glucosamine/heparan sulfate chain. The disulfated disaccharide was shown through its release by direct nitrous acid treatment to be situated in a GlcNSO3-IdUA(2-SO4)-GlcNSO3(3-SO4) sequence which is distinct from that in which 3-O-sulfated glucosamine is located in the antithrombin-binding region of heparins. Analyses of heparan sulfate from lens capsule, a nonvascular basement membrane, indicated the absence of sequences containing 3-O-sulfated glucosamine, although otherwise the sulfated disaccharides produced by hydrazine/nitrous acid/Na-B3H4 treatment (GlcUA beta 1----4AnManH2(6-SO4), IdUA alpha 1----4AnManH2(6-SO4), IdUA(2-SO4)alpha 1----4AnManH2 and IdUA(2-SO4)alpha 1----4AnManH2(6-SO4] were the same as from GBM. Examination of the GBM heparan sulfate domains after nitrous acid treatment indicated that the O- as well as N-sulfate groups are clustered in an iduronic acid-rich 10-disaccharide peripheral segment, while the internal region (approximately 20 disaccharides) is composed primarily of repeating GlcUA beta 1----4GlcNAc units. The localization of chain diversity to the outer region may facilitate interactions of the heparan sulfate with other macromolecular components.