Isolation and characterization of sulphated mucopolysaccharides from rat leukaemic (RBL-1) basophils.

Proteoglycans of 300 000 mol.wt. were isolated from dispersed rat basophil tumour cells after labelling of the sulphated mucopolysaccharides with 35S in vitro:90% of the 35S-labelled mucopolysaccharides were extracted at high salt concentration. Alkali degradation of the 35S-labelled proteoglycans yielded glycosaminoglycan chains of 40 000 mol.wt. The composition of the salt-extracted 35S-labelled mucopolysaccharides, as defined by parallel or sequential degradation with chondroitinase AC, chondroitinase ABC and heparinase and resolution of the disaccharide-digestion products obtained with chondroitinase AC, was 48--61% chondroitin 4-sulphate, 20--30% dermatan sulphate, 10--15% heparin and 7--9% chondroitin 6-sulphate. Most of the salt-extracted 35S-labelled mucopolysaccharides were highly charged, with heparin and chondroitin 6-sulphate being relatively uniform in this regard, whereas chondroitin 4-sulphate and dematan sulphate exhibited a range of charge characteristics. The diversity of sulphated mucopolysaccharides present in the rat leukaemic basophil is in contrast with the predominance of heparin in the rat mast cell.     

Characterization of newly synthesized proteoglycans from rabbit menisci in organ culture.

Rabbit menisci were incubated with Na2 35SO4 in short-term organ culture to label newly synthesized proteoglycans. The radioactive products present in both tissue and culture medium were characterized separately with respect to distribution after ultracentrifugation in CsCl isopycnic density gradients, hydrodynamic size, interaction with hyaluronic acid, and glycosaminoglycan composition (types, size and content). Analysis of proteoglycan size by gel-filtration chromatography of the most-dense CsCl fractions (A1) on Sephacryl S-500 (associative conditions) resolved three species. A peak with Kav. approx. 0.7 was present in each chromatogram, and constituted the principal component in tissue extracts. Two other peaks with Kav. values of approx. 0.2 and 0.45 were also found. When the A1 fraction from tissue was subjected to CsCl-density-gradient ultracentrifugation under dissociative conditions, 71% of the recovered radioactivity was present in the most dense (A1D1) fraction. Incubation with hyaluronic acid of either A1 or A1D1 fraction from associative extract did not alter the apparent size of the labelled product, indicating a lack of aggregate formation. Meniscal proteoglycans showed an unusual and marked tendency to adsorb irreversibly to agarose and agarose-containing gel-filtration-chromatography media. High-pressure liquid-chromatographic analyses indicated that the sulphated glycosaminoglycans consisted of chondroitin 6-sulphate (72%), chondroitin 4-sulphate (19%) and dermatan sulphate (5%). Endo-beta-galactosidase (keratanase) digestion of the material failed to detect the presence of keratan sulphate. Of the labelled glycosaminoglycans, 95% was eluted from Sephacryl S-400 as a single symmetrical peak with a Kav. of 0.5. The results of studies with tissue extracts and culture medium were similar.     

Biosynthesis of glycosaminoglycans by cultured mastocytoma cells

Biosynthesis of glycosaminoglycans by several lines of cultured neoplastic mouse mast cells was studied by incorporation of [³⁵S]sulphate (and in some cases [6-³H]glucosamine) into macromolecular materials found in both the cells and their growth media. Such intracellular and extracellular radioactively labelled materials (shown to be glycosaminoglycans by susceptibility to digestion with heparinase) were further characterized by ion-exchange chromatography and by digestion with testicular hyaluronidase and chondroitinase. All but one cell line produced chondroitin sulphate as the major sulphated glycosaminoglycan; the remainder of the glycosaminoglycan was heparin-like material. No [³H]hyaluronic acid was synthesized. Cells of a newly derived line, termed P815S, synthesized more glycosaminoglycan than the other lines. This glycosaminoglycan, found in both cells and growth medium, was almost entirely chondroitin 4-sulphate. No chondroitin 6-sulphate was found. The chondroitin 4-sulphate from the cells was shown by gel filtration to be smaller than the chondroitin 4-sulphate in the media of these cultures. This discovery of relatively high proportions of chondroitin 4-sulphate in these mastocytoma-derived cells is noteworthy, since mast cells have generally been considered to produce heparin as their major glycosaminoglycan.     

The biosynthesis in vitro of keratan sulphate in bovine cornea

1. Bovine corneas were incubated in vitro with [U-(14)C]glucose. 2. The glycosaminoglycans of corneal stroma were isolated and fractionated on cetylpyridinium chloride-cellulose columns. The major components were keratan sulphate (71%), chondroitin 4-sulphate (17%) and chondroitin 6-sulphate (4%). 3. The acid-soluble nucleotides and intermediates of glycosaminoglycan biosynthesis of corneal stroma were separated on Dowex 1 (formate form) and the tissue content and cellular concentrations were determined. 4. The rates of synthesis of the intermediates of glycosaminoglycan biosynthesis in corneal stroma were determined. 5. The incorporation of radioactivity from [U-(14)C]glucose into the uronic acid and hexosamine components of the glycosaminoglycans present in corneal stroma were measured and the turnover rates of these polymers were calculated. It was found that keratan sulphate was turning over in about 723h and chondroitin 6-sulphate in 251h.     

Comparative study on glycosaminoglycans synthesized in peripheral and peritoneal polymorphonuclear leucocytes from guinea pigs.

Glycosaminoglycans synthesized in polymorphonuclear (PMN) leucocytes isolated from blood (peripheral PMN leucocytes) and in those induced intraperitoneally by the injection of caseinate (peritoneal PMN leucocytes) were compared. Both peripheral and peritoneal PMN leucocytes were incubated in medium containing [35S]sulphate and [3H]glucosamine. Each sample obtained after incubation was separated into cell, cell-surface and medium fractions by trypsin digestion and centrifugation. The glycosaminoglycans secreted from peripheral and peritoneal PMN leucocytes were decreased in size by alkali treatment, indicating that they existed in the form of proteoglycans. Descending paper chromatography of the unsaturated disaccharides obtained by the digestion of glycosaminoglycans with chondroitinase AC and chondroitinase ABC identified the labelled glycosaminoglycans of both the cell and the medium fractions in peripheral PMN leucocytes as 55-58% chondroitin 4-sulphate, 16-19% chondroitin 6-sulphate, 16-19% dermatan sulphate and 6-8% heparan sulphate. Oversulphated chondroitin sulphate and oversulphated dermatan sulphate were found only in the medium fraction. In peritoneal PMN leucocytes there is a difference in the composition of glycosaminoglycans between the cell and the medium fractions; the cell fraction was composed of 60% chondroitin 4-sulphate, 5.5% chondroitin 6-sulphate, 16.8% dermatan sulphate and 13.9% heparan sulphate, whereas the medium fraction consisted of 24.5% chondroitin 4-sulphate, 28.2% chondroitin 6-sulphate, 33.7% dermatan sulphate and 10% heparan sulphate. Oversulphated chondroitin sulphate and oversulphated dermatan sulphate were found in the cell, cell-surface and medium fractions. On the basis of enzymic assays with chondro-4-sulphatase and chondro-6-sulphatase, the positions of sulphation in the disulphated disaccharides were identified as 4- and 6-positions of N-acetylgalactosamine. Most of the 35S-labelled glycosaminoglycans synthesized in peripheral PMN leucocytes were retained within cells, whereas those in peritoneal PMN leucocytes were secreted into the culture medium. Moreover, the amount of glycosaminoglycans in peritoneal PMN leucocytes was significantly less than that in peripheral PMN leucocytes. Assay of lysosomal enzymes showed that these activities in peritoneal PMN leucocytes were 2-fold higher than those in peripheral PMN leucocytes.     

Inhibition of hydroxyapatite crystal growth by bone proteoglycans and proteoglycan components

The small leucine-rich proteoglycans (SLRPs) interact with hydroxyapatite (HAP) and have been demonstrated to be important modulators of mineralisation. In the present study we have examined the effect of bone SLRPs, purified bone glycosaminoglycan (GAG) chains and core proteins as well as commercial chondroitin 4-sulphate, chondroitin 6-sulphate and desulphated chondroitin on HAP crystal growth. Seeded HAP growth experiments revealed that addition of bone GAG chains resulted in almost complete inhibition of crystal growth (93%), with addition of core proteins and intact PGs resulting in 55 and 37% inhibition, respectively. In contrast, commercial chondroitin 4-sulphate was significantly less inhibitory compared with the bone SLRPs and components, yielding only a 6% reduction in HAP-induced crystal growth at the same concentration. Significantly, chondroitin 6-sulphate was found to be noninhibitory, whilst desulphated chondroitin was inhibitory to seeded HAP growth. The data indicate that direct adsorption of SLRPs to growth sites and their ability to bind calcium are significant determinants in the inhibitory process. In addition, PG/GAG chemistry and the conformation of the macromolecules in solution have also been shown to be important. This work provides new information regarding the role of bone SLRPs and their components in the regulation of the mineralisation process.     

Isolation, characterization and properties of the oversulphated chondroitin sulphate proteoglycan from squid skin with peculiar glycosaminoglycan sulphation pattern.

Oversulphated chondroitin sulphate proteoglycan from squid skin was isolated from 4 M guanidine hydrochloride extract by ion-exchange chromatography, gel chromatography and density gradient centrifugation. The proteoglycan had Mr 3.5 x 10(5), contained on average six oversulphated chondroitin sulphate chains (Mr 4 x 10(4)) bound on a polypeptide of Mr 2.8 x 10(4), and oligosaccharides consisting of both hexosamines, glucuronic acid, sulphates and fucose as the only neutral monosaccharide. The major amino acids of the proteoglycan protein core are glycine (corresponding to about one third of the total amino acids), aspartic acid/asparagine and serine, together amounting to 50% of the total. The proteoglycan was resistant to the proteolytic enzymes V8 protease, trypsin (treated with diphenylcarbamoyl chloride), alpha-chymotrypsin and pronase, while it was completely degraded by papain and to a large extent by collagenase. Pretreated proteoglycan with chondroitinase AC was degraded by pronase to a large extent and slightly by V8 protease and trypsin. The proteoglycan did not interact with hyaluronic acid and did not form self-aggregates. Oversulphated chondroitin sulphate chains were composed of unusual sulphated disaccharide units which were isolated and characterized by HPLC. In particular, it contained 2-acetamido-2-deoxy-3-O-(alpha-L-threo-4-enopyranosyluronic acid)-D-galactose 4-sulphate (delta di-4S) and disulphated disaccharides (delta di-diS) [90% 2-acetamido-2-deoxy-3-O-(alpha-L-threo-4-enopyranosyluronic acid 2/3-sulphate)-D-galactose 6-sulphate (delta di-diSD) and 10% 2-acetamido-2-deoxy-3-O-(alpha-L-threo-4-enopyranosyluronic acid 2/3-sulphate)-D-galactose 4-sulphate (delta di-diSK)] as the major disaccharides, significant amounts of trisulphated disaccharides (delta di-triS) and small amounts of 2-acetamido-2-deoxy-3-O-(alpha-L-threo-4-enopyranosyluronic acid)-D-galactose 6-sulphate (delta di-6S) and 2-acetamido-2-deoxy-3-O-(alpha-L-threo-4-enopyranosyluronic acid)-D-galactose (delta di-OS). Trisulphated disaccharides contained sulphate groups at C-4 and C-6 of the galactosamine and at C-2 or C-3 of the glucuronic acid. By HPLC analysis of a pure preparation of oversulphated chondroitin sulphate, it was found that it contains glucose, galactose, mannose and fucose most likely as branches.     

The synthesis of glycosaminoglycans by cultures of rabbit corneal endothelial and stromal cells.

Confluent monolayer cultures of rabbit corneal endothelial and stromal cells were incubated independently with [35S]sulphate and [3H]glucosamine for 3 days. AFter incubation, labelled glycosaminoglycans were isolated from the growth medium and from a cellular fraction. These glycosaminoglycans were further characterized by DEAE-cellulose column chromatography and by sequential treatment with various glycosamino-glycan-degrading enzymes. Both endothelial and stromal cultures synthesized hyaluronic acid as the principal product. The cell fraction from the stromal cultures, however, had significantly less hyaluronic acid than that from the endothelial cultures. In addition, both types of cells synthesized a variety of sulphated glycosaminoglycans. The relative amounts of each sulphated glycosaminoglycan in the two cell lines were similar, with chondroitin 4-sulphate, chondroitin 6-sulphate and dermatan sulphate as the major components. Heparan sulphate was present in smaller amounts. Keratan sulphate was also identified, but only in very small amounts (1-3%). The presence of dermatan sulphate and the high content of hyaluronic acid are similar to the pattern of glycosaminoglycans seen in regenerating or developing tissues, including cornea.     

Isolation and partial characterization of proteoglycans from rat incisors.

Newly synthesized proteoglycans of rat incisors were labelled in vivo for 6h with [35S]-sulphate in order to facilitate their detection during purification and characterization. Proteoglycans were extracted from non-mineralized portions (predentine) of rat incisors with 4M-guanidinium chloride and subsequently from dentine by demineralization with a 0.4M-EDTA solution containing 4M-guanidinium chloride. Both extractions were performed at 4 degrees C in the presence of proteinase inhibitors. Purification of proteoglycans was achieved with a procedure involving gel-filtration chromatography, selective precipitation of phosphoproteins, affinity chromatography and ion-exchange chromatography. Two proteoglycan populations were found in the initial extract (Pd-PG I and Pd-PG II), whereas only one fraction (D-PG) was obtained after demineralization. The minor proteoglycan fraction from the first extract, Pd-PG I, although not totally characterized, differed sharply from the other proteoglycans in that it had a larger molecular size with larger glycosaminoglycan chains composed of chondroitin 4- and 6-sulphate isomers. In contrast, the major proteoglycans Pd-PG II and D-PG had smaller hydrodynamic sizes with smaller glycosaminoglycan chains (but larger than those from bovine nasal cartilage proteoglycans) composed exclusively of chondroitin 4-sulphate. The major proteoglycans were incapable of interacting with hyaluronic acid. In general, the amino acid compositions of the major proteoglycans of rat incisors resembled that of bovine nasal cartilage proteoglycans, but the former had lower proline, valine, isoleucine, leucine, and higher aspartic acid, contents.     

Glycosaminoglycan composition of human amniotic fluid

The glycosaminoglycan composition of human amniotic fluid between 12–21 weeks gestation has been studied by Dowex column chromatography coupled with enzymatic analyses of the specific glycosaminoglycan in each column fraction. The total uronic acid recovered from the columns consisted of “glycopeptides” (7%), hyaluronic acid (34%), nonsulfated chondroitin (14%), chondroitin-4-sulfate (13%), chondroitin-6-sulfate (20%), dermatan sulfate (5%), and heparan sulfate (6%). Based on these studies a simple screening procedure was devised to detect increased quantities of heparan sulfate and dermatan sulfate in 5–10-ml samples of amniotic fluid and tested in the antenatal diagnosis of Hurler and Hunter's syndrome. A false negative result was recorded in a Hunter fluid obtained early gestation and a false positive result recorded in a normal fluid obtained at weeks. These data suggest that the time in gestation when amniotic fluid is sampled for chemical analysis is an important variable affecting glycosaminoglycan composition in both normal and pathological pregnancies.     

Effect of trimethylcolchicinic acid on the synthesis and excretion of proteoglycans in tissue culture.

The action of trimethylcolchicinic acid on the synthesis and excretion of proteoglycans has been studied on the L cell strain. The incorporation of precursors has been measured, and proteoglycans produced in the culture medium have been extracted and their concentration determined. The mucopolysaccharide components have been studied by electrophoresis. Control cultures produce hyaluronic acid, dermatan sulfate and very low concentrations of chondroitin 4-sulphate or 6-sulphate. Cultures treated with trimethycolchicinic acid (4 mu g/ml) produce hyaluronic acid, very high concentrations of chondroitin 4-sulphate or 6-sulphate and only traces of dermatan sulphate. So, trimethylcolchicinic acid does not modify the synthesis of hyaluronic acid: it considerably increases the production of chondroitin 4-sulphate or 6-sulphate and inhibits the production of dermatan sulphate. Protein fraction of the proteoglycans is proportionally increased in treated cultures, but there is no marked difference between amino acid concentrations of proteoglycans extracted from control and treated cultures. A slight fall in the cystine concentrations was the only change in the amino acid content of proteoglycans extracted from treated cultures. A hypothesis to explain these results is discussed.     

Heparin binds to Leishmania donovani promastigotes and inhibits protein phosphorylation.

We show that promastigotes of Leishmania donovani, the causative agent of visceral leishmaniasis (kala-azar), possess heparin receptors on their surface. From a linear Scatchard plot of the binding data obtained using [3H]heparin and viable promastigotes, one derives a binding constant of 4.7 x 10(-7) M and an estimate of 860,000 receptors per parasite. The [3H]heparin bound to parasites could not be displaced by hyaluronic acid or by three other glycosaminoglycans (dermatan sulphate, chondroitin 4-sulphate and chondroitin 6-sulphate). It was demonstrated that exponential phase promastigotes growing in medium 199 supplemented with fetal bovine serum incorporate 35SO4 into a cell-associated macromolecule that has the properties of heparin proteoglycan. Heparin inhibits the activity of the cell-surface histone-protein kinase; incubation of viable promastigotes with [gamma-32P]ATP and MgCl2 (10 mM) in the absence and presence of heparin (0.01-0.5 mg/ml) for 10 min, followed by analysis by SDS/polyacrylamide-gel electrophoresis and autoradiography, revealed that the phosphorylation of 12 or 13 parasite proteins was inhibited by the glycosaminoglycan. These data suggest that heparin may play a role in the host-parasite relationship.     

Biosynthesis of chondroitin sulphate by a Golgi-apparatus-enriched preparation from cultures of mouse mastocytoma cells.

Mouse mastocytoma cells grown in suspension culture produce chondroitin 4-sulphate. A Golgi-apparatus-enriched fraction from these cells was prepared and examined for chondroitin-synthesizing activity. When Golgi-apparatus-enriched fractions were incubated with UDP-[14C]glucuronic acid and UDP-N-acetylgalactosamine, they demonstrated a greater than 13-fold increase in chondroitin-synthesizing activity over cell homogenates. Similar incubations with the addition of a pentasaccharide from chondroitin sulphate resulted in a greater than 40-fold increase in [14C]glucuronic acid-incorporating activity over cell homogenates. Other membrane fractions had much less activity, suggesting that the Golgi apparatus is the most active location for chondroitin biosynthesis. Products of the incubations indicated the formation of [14C]chondroitin glycosaminoglycan on endogenous primers and formation of [14C]-hexasaccharide and somewhat larger [14C]oligosaccharides on exogenous pentasaccharide acceptors. There was, however, a significant amount of large [14C]-chondroitin glycosaminoglycan formed on pentasaccharide, indicating that some pentasaccharide did serve as a true primer for polysaccharide synthesis.     

The effect of preganglionic stimulation on the incorporation of l-[U-14C]valine into the protein of the superior cervical ganglion of the guinea pig

The acid glycosaminoglycans were extracted from the skins of young rats less than 1 day post partum. The isolated products were fractionated by a cetylpyridinium chloride-cellulose column technique and identified by chemical analysis, electrophoretic mobility and susceptibility to testicular hyaluronidase digestion. Hyaluronic acid (56%) dermatan sulphate (15.6%) and chondroitin 6-sulphate (9.1%) were the major components, but chondroitin 4-sulphate, heparan sulphate and heparin were also present, together with two further fractions tentatively suggested to be a heparan sulphate-like fraction and a dermatan sulphate fraction, both of short chain length or low degree of sulphation.     

The kinetic of degradation of chondroitin of sulphates and hyaluronic acid by chondroitinase form Proteus vulgaris.

Km and Vmax. were determined for the degradation by chondroitinase of chondroitin 4-sulphate, 4-sulphate-proteoglycna, chondroitin 6-sulphate, dermatan sulphate and hyaluronic acid. Degradation of chondroitin 4-sulphate was inhibited by hyaluronic acid but not by keratan sulphate. The results are discussed with regard to the use to the use of chondroitinase as a sleective reagent for the degradation of tissue glycosaminoglycans.     

Human liver glucuronate 2-sulphatase. Purification, characterization and catalytic properties.

Human glucuronate 2-sulphatase (GAS), which is involved in the degradation of the glycosaminoglycans heparan sulphate and chondroitin 6-sulphate, was purified almost 2,000,000-fold to homogeneity in 8% yield from liver with a four-step six-column procedure, which consists of a concanavalin A-Sepharose/Blue A-agarose coupled step, a DEAE-Sephacel/octyl-Sepharose coupled step, CM-Sepharose chromatography and gel-permeation chromatography. Although more than 90% of GAS activity had a pI of greater than 7.5, other forms with pI values of 5.8, 5.3, 4.7 and less than 4.0 were also present. The pI greater than 7.5 form of GAS had a native molecular mass of 63 kDa. SDS/polyacrylamide-gel-electrophoretic analysis resulted in two polypeptide subunits of molecular mass 47 and 19.5 kDa. GAS was active towards disaccharide substrates derived from heparin [O-(beta-glucuronic acid 2-sulphate)-(1----4)-O-(2,5)-anhydro[1-3H]mannitol 6-sulphate (GSMS)] and chondroitin 6-sulphate [O-(beta-glucuronic acid 2-sulphate-(1----3)-O-(2,5)-anhydro[1-3H]talitol 6-sulphate (GSTS)]. GAS activity towards GSMS and GSTS was at pH optima of 3.2 and 3.0 respectively with apparent Km values of 0.3 and 0.6 microM respectively and corresponding Vmax values of 12.8 and 13.7 mumol/min per mg of protein respectively. Sulphate and phosphate ions are potent inhibitors of enzyme activity. Cu2+ ions stimulated, whereas EDTA inhibited enzyme activity. It was concluded that GAS is required together with a series of other exoenzyme activities in the lysosomal degradation of glycosaminoglycans containing glucuronic acid 2-sulphate residues.     

The biosynthesis in vitro of chondroitin sulphate in neonatal rat epiphysial cartilage

1. A system is described, which was used to incubate neonatal rat epiphysial cartilage in vitro with [U-(14)C]glucose and [(35)S]sulphate. 2. The acid glycosaminoglycans of neonatal rat epiphyses were extracted and fractionated on cetylpyridinium chloride-cellulose columns. The major components were chondroitin 4-sulphate (65%), chondroitin 6-sulphate (15%), hyaluronic acid (4%) and keratan sulphate (2%). 3. The acid-soluble nucleotides and intermediates of glycosaminoglycan synthesis were separated on a Dowex 1 (formate) system. The tissue contents and cellular concentrations of these metabolites were determined. 4. The rates of synthesis of UDP-glucuronic acid and UDP-N-acetyl-hexosamine from [U-(14)C]glucose were found to be 0.79+/-0.16 and 3.2+/-0.08nmol/min per g wet wt. respectively. 5. The incorporation of [U-(14)C]glucose into the uronic acid and hexosamine moieties of the polymers was also measured and the turnover rates of the glycosaminoglycans were calculated. It was found that chondroitin sulphate was turning over in about 70h and hyaluronic acid in about 120h. 6. The relative rates of synthesis of the sulphated glycosaminoglycans were calculated from [(35)S]sulphate incorporation and were found to be in good agreement with those obtained from [U-(14)C]glucose labelling.     

The disaccharides formed by deaminative cleavage of N-deacetylated glycosaminoglycans.

Chondroitin 4-sulphate, chondroitin 6-sulphate, dermatan sulphate and keratan sulphate were N-deacetylated by treatment with hydrazine and then cleaved with HNO2 at pH 4.0, and the resulting products were reduced with NaB3H4. This reaction sequence cleaved the glycosaminoglycans at their N-acetyl-D-glucosamine or N-acetyl-D-galactosamine residues, which were converted into 3H-labelled 2,5-anhydro-D-mannitol (AManR) or 2,5-anhydro-D-talitol (ATalR) residues respectively. The end-labelled disaccharides, composed of D-glucuronic acid (GlcA), L-iduronic acid (IdoA) or D-galactose (Gal) and one of the anhydrohexitols, were identified as follows: both chondroitin 4-sulphate and chondroitin 6-sulphate gave GlcA----ATalR(4-SO4), GlcA----ATalR(6-SO4), IdoA----ATalR (4-SO4) and GlcA(2-SO4)----ATalR(6-SO4); dermatan sulphate gave IdoA----ATalR(4-SO4), GlcA----ATalR(4-SO4), GlcA----ATalR(6-SO4)----IdoA(2-SO4)ATalR(4-SO4) and IdoA----ATalR (4,6-diSO4); keratan sulphate gave Gal(6-SO4)----AManR(6-SO4), Gal----AManR(6-SO4), Gal(6-SO4)----AManR and Gal----AManR. Several additional disaccharides were generated by treatment of the uronic acid-containing disaccharides with hydrazine to epimerize their uronic acid residues at C-5. A number of these disaccharides were found to be substrates for lysosomal sulphatases and glycuronidases. Methods were developed for the separation of all of the disaccharide products by h.p.l.c. The rate of N-deacetylation of chondroitin 4-sulphate by hydrazinolysis was significantly lower than the rate of N-deacetylation of chondroitin 6-sulphate or chondroitin. Dermatan sulphate was N-deacetylated at an intermediate rate. The relative amounts of disaccharides obtained from chondroitin 4-sulphate, chondroitin 6-sulphate and dermatan sulphate under optimum hydrazinolysis/deamination conditions were comparable with the amounts of the corresponding products released from the polymers by chondroitinase treatment.     

Urinary excretion of sulphated N-acetylhexosamines in patients with various mucopolysaccharidoses.

Sulphated N-acetylhexosamines have been isolated from human urine and tentatively identified as N-acetylglucosamine 6-sulphate (GlcNAc6S), N-acetylgalactosamine 6-sulphate (GalNAc6S), N-acetylgalactosamine 4-sulphate (GalNAc4S) and N-acetylgalactosamine 4,6-disulphate (GalNAc4,6diS). Urine from mucopolysaccharidosis-Type-IIID, -IVA and -VI patients compared with that from normal individuals contains elevated levels of GlcNAc6S (380-fold), GalNAc6S (180-fold) and GalNAc4S (420-fold) respectively. Urine from mucopolysaccharidosis-Type-VI patients also contain more than 600 times the normal level of GalNAc4,6diS. Urine from a mucolipidosis-Type-II and a multiple-sulphatase-deficient patient, and, in general, all mucopolysaccharidosis patients studied, contain at least 5-10-fold elevations of sulphated N-acetylhexosamines over the levels detected in urine from normal controls and a alpha-mannosidosis patient. Urine from patients with clinically mild phenotypes contains less sulphated N-acetylhexosamines than isolated from urine of clinically severe mucopolysaccharidosis patients. The source of the four sulphated N-acetylhexosamines is not known. However, incubation of a series of oligosaccharide substrates, derived from keratan sulphate and chondroitin 6-sulphate and containing non-reducing-end beta-linked 6-sulphated N-acetylhexosamine residues, with homogenates of cultured human skin fibroblasts has indirectly been shown to release GlcNA6S and GalNAc6S respectively. Release of GalNAc4S could not be demonstrated in similar incubations of oligosaccharide substrates derived from chondroitin 4-sulphate and containing non-reducing-end beta-linked GalNAc4S residues. We propose that some, if not all, of the sulphated N-acetylhexosamine present in human urine is derived from the action of beta-N-acetylhexosaminidase on sulphated GlcNAc or GalNAc residues at the non-reducing end of keratan sulphate, dermatan sulphate or chondroitin sulphate.     

Effect of magnesium deficiency on the metabolism of glycosamino-glycans in rats

Magnesium deficiency in rats has significant effect on the concentration of different glycosaminoglycans in the tissues, the nature of the change being different in different tissues. Total glycosaminoglycans, chondroitin-4-sulphate + chondroitin-6-sulphate and dermatan sulphate increased in the aorta while hyaluronic acid, heparan sulphate and heparin decreased. In the liver, total glycosaminoglycans, hyaluronic acid, chondroitin-4-sulphate + 6-sulphate and heparin decreased while total glycosamino-glycans and all the glycosaminoglycan fractions increased in the heart. In the kidney, total glycosaminoglycans showed no significant alteration, hyaluronic acid and heparin decreased while chondroitin-4-sulphate + 6-sulphate increased. Activity of biosynthetic enzymesviz. glucosamine-o-phosphate isomerase and UDPG-dehydrogenase showed decrease in the liver. The concentration of 3’-phosphoadenosine 5’-phosphosulphate, activity of sulphate activating system and sulphotransferase were also similarly altered in the liver in magnesium deficiency.