Developmental changes in glycosaminoglycan sulfotransferase activities in animal sera

Glycosaminoglycan sulfotransferase activities in sera during the prenatal and postnatal development of the ox, rat, and chicken were systematically measured with chemically desulfated cartilage chondroitin 4-sulfate, cornea keratan sulfate, and kidney heparan sulfate as exogenous sulfate acceptors and with [35S]sulfate-labeled 3'-phosphoadenosine 5'-phosphosulfate as a sulfate donor. The results of specificity studies and product analyses indicated that these enzymes introduce sulfates at position 6 of the internal N-acetylgalactosamine units of chondroitin, position 6 of the galactose units of keratan sulfate, and position 2 (an amino group) of the glucosamine units of heparan sulfate, respectively. The results of the enzyme assays indicated that (1) the three activities change in a development-associated manner in each animal species, (2) generally, the activities of the former two enzymes decrease with embryonic development and aging after birth, although in chicken serum they increase transiently at the late prenatal stage and decrease thereafter, and (3) the pattern of the changes in heparan sulfate sulfotransferase activity is species-dependent: the activity increases in the rat, decreases in the ox, and does not significantly change in the chicken during prenatal or postnatal development. These alterations may reflect development-associated biosynthesis of the corresponding glycosaminoglycans or maturation of the proteoglycans in some tissues.     

Difference between N-acetylgalactosamine 4-sulfate 6-O-sulfotransferases from human serum and squid cartilage in specificity toward the terminal and interior portion of chondroitin sulfate

In the preceding paper (Inoue, H., Otsu, K., Yoneda, M., Kimata, K., Suzuki, S., and Nakanishi, Y. (1986) J. Biol. Chem. 261, 4460-4469), we reported the purification from human serum of an N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase fraction which was able to transfer sulfate predominantly to position 6 of the nonreducing terminal N-acetylgalactosamine 4-sulfate unit of chondroitin sulfate. We now show that the activity toward the terminal was co-purified with a minor activity toward the interior counterpart by sequential chromatography on heparin-Sepharose CL-6B, Matrex Blue B, hydroxyapatite, and Sephacryl S-300, and that the two activities were equally heatlabile. The enzyme purified 5000-fold from human serum was devoid of the sulfotransferase activities toward chondroitin, heparan sulfate, and keratan sulfate, but showed a strong terminal sulfotransferase activity toward dermatan sulfate (pig skin); over 97% of the sulfate residues incorporated were at position 6 of the nonreducing N-acetylgalactosamine 4,6-bissulfate end groups linked to the L-iduronic acid group. Although the enzyme introduces sulfate predominantly into the nonreducing terminal of chondroitin sulfate at physiological pH (approximately equal to 7.0) and Ca2+ concentration (approximately 2-3 mM), the activity toward the interior portion relative to that toward the terminal was increased by either lowering pH or elevating Ca2+ concentration, perhaps owing to changes in the conformation or ionic state of the acceptor molecule. Comparison between the human serum enzyme and the N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase (formerly designated "E6-sulfotransferase") from squid cartilage indicated that the latter is distinct from the former in introducing sulfate predominantly into the interior portion of chondroitin sulfate. It appears that the role of the squid sulfotransferase is to synthesize so-called chondroitin sulfate E where over 50% of the interior hexosamine units are 4,6-bis-sulfated.     

Purification and characterization of N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase from the squid cartilage

N-Acetylgalactosamine 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST), which transfers sulfate from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to position 6 of N-acetylgalactosamine 4-sulfate in chondroitin sulfate and dermatan sulfate, was purified 19,600-fold to apparent homogeneity from the squid cartilage. SDS-polyacrylamide gel electrophoresis of the purified enzyme showed a broad protein band with a molecular mass of 63 kDa. The protein band coeluted with GalNAc4S-6ST activity from Toyopearl HW-55 around the position of 66 kDa, indicating that the active form of GalNAc4S-6ST may be a monomer. The purified enzyme transferred sulfate from PAPS to chondroitin sulfate A, chondroitin sulfate C, and dermatan sulfate. The transfer of sulfate to chondroitin sulfate A and dermatan sulfate occurred mainly at position 6 of the internal N-acetylgalactosamine 4-sulfate residues. Chondroitin sulfate E, keratan sulfate, heparan sulfate, and completely desulfated N-resulfated heparin were not efficient acceptors of the sulfotransferase. When a trisaccharide or a pentasaccharide having sulfate groups at position 4 of N-acetylgalactosamine was used as acceptor, efficient sulfation of position 6 at the nonreducing terminal N-acetylgalactosamine 4-sulfate residue was observed.     

Paper disk assay for glycosaminoglycan sulfotransferases

A method is described for the assay of sulfotransferases, which transfer sulfate from 3'-phosphoadenosine-5'-phosphosulfate (PAPS) to glycosaminoglycan acceptors. Following the sulfation reactions, the [35S]sulfate-labeled products are precipitated and then separated from a sulfate donor ([35S]PAPS) and its degradation products by a paper disk method, and then the radioactivity remaining on the paper disk is subsequently determined by liquid scintillation counting. The rapidity and simplicity of the method are advantageous for multiple assays and have allowed us to establish assay conditions for serum sulfotransferases which introduce sulfate at position 6 of the internal N-acetylgalactosamine units of chondroitin, position 2 (amino group) of the glucosamine units of heparan sulfate and sugar units of keratan sulfate, respectively. The assay method will be applicable with modification to the assay of other glycosaminoglycan sulfotransferases and glycoprotein sulfotransferases.     

Regulation of serum glycosaminoglycan sulfotransferase activities: inhibition by sulfated glycosaminoglycans and activation by polyamines and basic peptides including a polylysine-containing segment of the c-Ki-ras 2 protein

The regulatory mechanisms for the glycosaminoglycan sulfotransferases in fetal calf serum were investigated. The enzymes examined were those which transfer sulfate from 3'-phosphoadenosine 5'-phosphosulfate to 1) position 6 of the internal N-acetylgalactosamine units of chondroitin, 2) position 6 of galactose units of keratan sulfate, and 3) position 2 (an amino group) of glucosamine units of heparan sulfate. The former two enzymes were activated by spermidine, spermine, protamine, and poly L-lysine. All the enzymes were strongly inhibited by heparin and dextran sulfate, whereas only the chondroitin 6-O-sulfotransferase was inhibited by sulfated galactosaminoglycans. The inhibition of this enzyme by the sulfated glycosaminoglycans was abolished by polylysine, indicating that the activation by polylysine is partly due to the neutralization of endogenous acidic inhibitors, including sulfated glycosaminoglycans. Affinity chromatographic studies demonstrated that heparin specifically binds to the three enzymes, which have anionic isoelectric points, and that chondroitin 6-sulfate, spermine, and polylysine bind to the former two enzymes under physiological conditions. Thus, the activation by spermine and polylysine as well as the inhibition by sulfated glycosaminoglycans also appears to occur through their binding to the enzymes. Studies with synthetic lysine oligomers and an affinity-purified (approximately 700-fold) fraction containing the former two enzymes indicated that the pentamer is the minimum unit required for the activation. A synthetic peptide, containing six consecutive lysines at the carboxy terminus of the human c-Ki-ras 2 protein, also regulated the two enzyme activities at micromolar concentrations. The possible physiological implications of the observed effects of these regulatory substances on the glycosaminoglycan sulfotransferases are discussed in relation to glycosaminoglycan synthesis during the proliferation, differentiation, and transformation of cells. The possibility of sulfated glycosaminoglycans being enzyme regulators is also discussed.     

Separation and properties of five glycosaminoglycan sulfatases from rat skin.

Chondroitin sulfates, dermatan sulfate, heparan sulfate, heparin, keratan sulfate, and oligosaccharides derived from these sulfated glycosaminoglycans have been used for the measurement of sulfatase activity of rat skin extracts. Chromatographic fractionation of the extracts followed by specificity studies demonstrated the existence of five different sulfatases, specific for 1) the nonreducing N-acetylglucosamine 6-sulfate end groups of heparin sulfate and keratan sulfate, 2) the nonreducing N-acetylgalactosamine (or galactose) 6-sulfate end groups of chondroitin sulfate (or keratan sulfate), 3) the nonreducing N-acetylgalactosamine 4-sulfate end groups of chondroitin sulfate and dermatan sulfate, 4) certain suitably located glucosamine N-sulfate groups of heparin and heparan sulfate, or 5) certain suitably located iduronate sulfate groups of heparan sulfate and dermatan sulfate. Two arylsulfatases, one of which was identical in its chromatographic behaviors with the third enzyme described above, were also demonstrated in the extracts. These results taken together with those previously obtained from studies on human fibroblast cultures suggest that normal skin fibroblasts contain at least five specific sulfatases and diminished activity of any one may result in a specific storage disease.     

Partial purification and characterization of 3'-phosphoadenylylsulfate:keratan sulfate sulfotransferases

Two 3'-phosphoadenylylsulfate:keratan sulfate sulfotransferases were purified 600-fold and 340-fold, respectively, from isolated bovine cornea cells. Sulfotransferase I exhibited an apparent Mr = 220,000, whereas an Mr = 140,000 was calculated for sulfotransferase II. The final preparations were both devoid of chondroitin sulfate sulfotransferase activity. The position of sulfation was determined by proton nuclear magnetic resonance spectroscopy. Sixty per cent of the sulfate ester groups formed by sulfotransferase I were linked to the C-6 atom of galactosyl residues, the other ones to the C-6 atom of N-acetylglucosamine. Sulfotransferase II showed a different specificity: 23% of the newly formed sulfate ester groups were on galactosyl and 77% on N-acetylglucosaminyl residues. Both sulfotransferase preparations acted in a cooperative manner. In the presence of both sulfotransferases, the incorporation of [35S]sulfate into keratan sulfate was up to 75% higher than could be expected from the sum of individual activities. From the specific radioactivities of the oligosaccharides produced by digestion with endo-beta-galactosidase, it was also concluded that both enzyme species reacted best with keratan sulfate segments exhibiting a relatively high degree of sulfation.     

Enzymatic sulfation of galactose residue of keratan sulfate by chondroitin 6-sulfotransferase

We have previously found that the purified chondroitin 6-sulfotransferase(C6ST), which transfers sulfate from 3'-phosphoadenosine 5'-phosphosulfate(PAPS) to position 6 of N-acetylgalactosamine in chondroitin,catalyzed the sulfation of keratan sulfate, and that both theC6ST activity and the keratan sulfate sulfotransferase (KSST)activity were expressed in COS-7 cells when C6ST cDNA was transfected.In this report we describe some properties of the KSST activitycontained in the purified C6ST, and characterize the sulfatedproducts formed from keratan sulfate and partially desulfatedkeratan sulfate. Optimal pH, requirement for cationic activators,and K_m value for PAPS of the KSST activity were very similarto those of the C6ST activity. ³⁵S-Labeled glycosaminoglycansformed from keratan sulfate and partially desulfated keratansulfate were N-deacetylated by treatment with hydrazine/hydrazinesulfate and then cleaved with HNO₂ at pH 4, and the resultingproducts were reduced with NaB³H₄. Analysis of the degradationproducts with paper chromatography and high performance liquidchromatography provided evidence that C6ST transferred sulfateto position 6 of galactose residue which was glycosidicallylinked to N-acetylglucosamine 6-sulfate residue or to N-acetylglucosamineresidue. Northern blot analysis using poly (A)⁺ RNA from 12-d-oldchick embryos indicated that the message of C6ST was expressednot only in the cartilage but also in the cornea in which keratansulfate is actively synthesized. chondroitin sulfate keratan sulfate glycosaminoglycan sulfotransferase hydrazinolysis deaminative cleavage     

Purification and characterization of a 3'-phosphoadenylylsulfate:chondroitin 6-sulfotransferase from arterial tissue

A 3'-phosphoadenylylsulfate:chondroitin sulfotransferase (EC 2.8.2.5) was purified to homogeneity (about 760-fold) from the cytosolic fraction of calf arterial tissue by Con A-Sepharose, ion exchange and affinity chromatography. The enzyme has a molecular mass of 38000 Da, optimal activity at pH 6.0 (100%) and 7.25 (75%), requires divalent cations for maximal activity (Mn2+ greater than Mg2+, Ca2+) and exhibits specificity towards desulfated chondroitin sulfate and oligosaccharides derived therefrom. The enzyme transfers sulfate groups from [35S]phosphoadenylylsulfate exclusively to C-6 OH groups of N-acetylgalactosamine units of the acceptor substrates. Maximal sulfate transfer occurs at 2mM chondroitin disaccharide units (100%), the transfer rates decreasing with decreasing chain length in the order deca (55%), octa (17%) and hexasaccharides (4%). Lineweaver-Burk plots revealed equal maximal velocities for chondroitin, deca-, octa- and hexasaccharide, but decreasing Km values. Chondroitin 4-sulfate has 21% of the acceptor potency exhibited by chondroitin, whereas dermatan sulfate, heparan sulfate and hyaluronate and the chondroitin tetrasaccharide showed no acceptor properties. Analysis of the reaction products formed by prolonged enzymatic sulfation of a reduced chondroitin hexasaccharide [GlcA-GalNAc]2-GlcA-GalNAc-ol revealed that the preterminal N-acetylgalactosamine from the non-reducing end and the internal N-acetylgalactosamine but not the N-acetylgalactosaminitol were sulfated and that no hexasaccharide disulfate was formed by the action of chondroitin 6-sulfotransferase. Chondroitin 6-sulfotransferase is considered to possess a binding region capable of accommodating a nonsulfated oligosaccharide sequence of at least six sugars and is believed to act in the course of chondroitin sulfate synthesis in cooperation with, but shortly after, the enzymes involved in the chain elongation reaction.     

A terminal 6-sulfotransferase catalyzing a synthesis of N-acetylgalactosamine 4,6-bissulfate residue at the nonreducing terminal position of chondroitin sulfate

A soluble enzyme from quail oviduct which incorporates sulfate into position 6 of the nonreducing N-acetylgalactosamine 4-sulfate end group of chondroitin sulfate has been purified. This enzyme (termed "terminal 6-sulfotransferase") was partially separated from a 6-sulfotransferase present in the same tissue which catalyzes the incorporation of sulfate into interior portion of unsulfated chondroitin. The basic requirements for the terminal 6-sulfotransferase reaction were shown to be 3'-phosphoadenylyl sulfate (donor) and chondroitin 4-sulfate (acceptor). The substitution of unsulfated chondroitin (prepared from squid skin) for chondroitin 4-sulfate resulted in a total loss of activity. These results suggest that the organization of the proteoglycan-synthesizing apparatus may well involve hitherto unrecognized mechanisms for the sulfation of chondroitin chains.     

Spondyloepiphyseal dysplasia, chondroitin sulfate type: a possible defect of PAPS--chondroitin sulfate sulfotransferase in humans

Four patients with an unusual form of spondyloepiphyseal dysplasia excreted in the urine undersulfated chondroitin 6-sulfate (Biochem. Med. $\text{7}$, 415–423, 1973). The sera of these patients show a low activity of PAPS — chondroitin sulfate sulfotransferase, while the undersulfated chondroitin sulfate present in their urine is a much better acceptor of ${}^{35}\text{SO}{}_4$ than standard chondroitin sulfate when they are incubated with [${}^{35}\text{S}$]PAPS and normal sulfotransferases. These results suggest that in these patients the skeletal lesions are secondary to a defect in the synthesis of chondroitin sulfate involving specifically the sulfotransferase activity.     

The glycosaminoglycans of estrogen-induced medullary bone in Japanese quail

Glycosaminoglycans were isolated from the femurs of estrogen-treated male Japanese quail. During the 72 h after the injection of estrogen the incorporation of a 1-h pulse of H₂³⁵SO₄ into keratan sulfate increased more than 100-fold in a pattern corresponding to the production of the induced medullary bone. The rate of incorporation into chondroitin 4-sulfate, the only other glycosaminoglycan detected, remained constant throughout the same time period. The rate of incorporation of the 1-h pulse of sulfate into chondroitin 4-sulfate and keratan sulfate was the same at 48 h of estrogen treatment. When birds (48 h estrogen) were allowed to live 6 h after the injection of the isotope, chondroitin 4-sulfate accumulated 5-fold over that found for similar animals labeled for only 1 h. Keratan sulfate, into which the isotope was incorporated at the same rate as the chondroitin sulfate in this experiment, did not accumulate much more in 6 h of labeling than in 1 h of labeling. This suggests that the keratan sulfate turns over more rapidly than the chondroitin 4-sulfate in this tissue. Autoradiography showed that the chondroitin 4-sulfate was associated mainly with the marrow cells near the cortical bone and the keratan sulfate with the newly synthesized medullary bone. These results suggest that keratan sulfate is a specific marker for this secondary bone matrix.     

Human N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase cDNA is related to human B cell recombination activating gene-associated gene

N-Acetylgalactosamine 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST) transfers sulfate from 3'-phosphoadenosine 5'-phosphosulfate to position 6 of N-acetylgalactosamine 4-sulfate (GalNAc(4SO(4))) in chondroitin sulfate and dermatan sulfate. We have previously purified the enzyme to apparent homogeneity from the squid cartilage. We report here cloning and characterization of human GalNAc4S-6ST. The strategy for identification of human GalNAc4S-6ST consisted of: 1) determination of the amino acid sequences of peptides derived from the purified squid GalNAc4S-6ST, 2) amplification of squid DNA by polymerase chain reaction, and 3) homology search using the amino acid sequence deduced from the squid DNA. The human GalNAc4S-6ST cDNA contains a single open reading frame that predicts a type II transmembrane protein composed of 561 amino acid residues. The recombinant protein expressed from the human GalNAc4S-6ST cDNA transferred sulfate from 3'-phosphoadenosine 5'-phosphosulfate to position 6 of the nonreducing terminal and internal GalNAc(4SO(4)) residues contained in chondroitin sulfate A and dermatan sulfate. When a trisaccharide and a pentasaccharide having sulfate groups at position 4 of N-acetylgalactosamine residues were used as acceptors, only nonreducing terminal GalNAc(4SO(4)) residues were sulfated. The nucleotide sequence of the human GalNAc4S-6ST cDNA was nearly identical to the sequence of human B cell recombination activating gene-associated gene.     

Mucopolysaccharidases from Pseudomonas sp. Isolation and partial characterization of constitutive enzymes involved in the degradation of keratan sulfate and chondroitin sulfate

Four constitutive enzymes, capable of degrading keratan sulfate, were isolated from Pseudomonas sp.: a particulate endoglycosidase, a soluble endoglycosidase, a soluble exo-beta-D-galactosidase and a soluble exo-beta-D-N-acetylglucosaminidase. The endoglycosidases were shown to act only upon keratan sulfate forming beta-D-2-acetamido-2-deoxy-6-O-sulfoglucosyl-(1----3)-D-galactose, as the main product. This results indicates that the enzyme catalyses the hydrolysis of beta-D-galactose-(1----4)-N-acetylglucosamine linkages. It was also shown that this monosulfated disaccharide inhibits the particulate keratan sulfate endoglycosidase. The bovine nucleus pulposus keratan sulfate is depolymerized at a lower rate and extent when compared to the corneal keratan sulfate. The soluble endoglycosidase is very labile, in contrast to the particulate enzyme, which has been stored at -20 degrees C or at 4 degrees C for at least 12 months with no loss in activity. The particulate endoglycosidase and the soluble exo-beta-D-galactosidase and exo-beta-D-N-acetylglucosaminidase are induced when the bacteria is grown in adaptative media containing either 0.1% keratan sulfate or 0.1% chondroitin sulfate. Furthermore, particulate forms of the exoenzymes were detected. The soluble endoglycosidase specific activity, in contrast, is approximately the same in extracts of cells grown in glucose, keratan sulfate or chondroitin sulfate. A chondroitin sulfate lyase was also identified in the soluble extracts of Pseudomonas sp. cells. This enzyme depolymerizes chondroitin 4-sulfate, chondroitin 6-sulfate and hyaluronic acid forming unsaturated disaccharides as main products. It is also active upon the glucuronic-acid-containing regions of the dermatan sulfate molecules. The properties of the soluble enzymes, further purified by ion-exchange chromatography, and of the particulate keratan sulfate endoglycosidase are presented.     

A sulfotransferase-sulfatase system in avian oviduct which catalyzes a conversion of UDP-N-acetylgalactosamine 4-sulfate to the 6-sulfate isomer

Magnum from quail oviduct was subfractionated to yield epithelium and tubular glands. The in vitro enzymatic activities involved in sulfated sugar nucleotide biosynthesis were assayed in these isolated tissues. The results demonstrated that the activities necessary for a series of reactions, UDP-N-acetylgalactosamine----UDP-N-acetylgalactosamine 4-sulfate----UDP-N-acetylgalactosamine 4,6- bisulfate ----UDP-N-acetylgalactosamine 6-sulfate, are located predominantly in the tubular gland. Both time course and pulse-chase studies with [35S]sulfate gave results that were consistent with this reaction scheme. A microsomal preparation from the magnum was shown to be capable of labeling all three sulfate sugar nucleotides with [35S]sulfate upon incubation with UDP-N-acetylgalactosamine and 3'- phosphoadenylyl [35S]sulfate. Again, their relative labeling rates were in the order necessary to allow for a synthesis of sulfated sugar nucleotides in the sequence described above. Furthermore, incubation of the microsomal preparation with UDP-N-[14C]acetylgalactosamine 4-sulfate and 3'- phosphoadenylyl sulfate resulted in the formation of UDP-N-[14C]acetylgalactosamine 6-sulfate. Also shown was the existence in the microsomal preparation of a sulfatase specific for the sulfate at position 4 of UDP-N-acetylgalactosamine 4,6- bisulfate . The results, together with those obtained in previous investigations, suggest that the tubular gland of quail oviduct contains a microsomal multienzyme system which catalyzes a series of sulfation and desulfation of N-acetylgalactosamine residues at the nonreducing terminal position of either sugar nucleotides or polysaccharide chains.     

Immunohistochemical techniques for detection of dermatan sulfate proteoglycan in tissue sections

Dermatan sulfate proteoglycan chains were detected in tissue sections treated with chondroitin B-lyase (0.01 units/ml) in 20 mM Tris-HCl (pH 8.0) for 1 hr, followed by staining with antibody 9A2 specific for unsaturated uronic acid coupled to N-acetylgalactosamine-4 sulfate. In contrast, after treatment with chondroitin B-lyase, no positive staining was observed with antibodies 3B3 and 1B5 which react to the unsaturated uronic acid coupled to N-acetylgalactosamine 6-sulfate and unsaturated uronic acid coupled to N-acetylgalactosamine, respectively. The distribution of dermatan sulfate thus revealed was confirmed by comparison with that found by monoclonal antibody 6B6 which reacts with small proteoglycans carrying dermatan sulfate side chains. The localization of positive staining in fibrous connective tissues was almost identical with these two procedures.     

Isolation and characterization of developmentally regulated chondroitin sulfate and chondroitin/keratan sulfate proteoglycans of brain identified with monoclonal antibodies

A panel of monoclonal antibodies prepared to the chondroitin sulfate proteoglycans of rat brain was used for their immunocytochemical localization and isolation of individual proteoglycan species by immunoaffinity chromatography. One of these proteoglycans (designated 1D1) consists of a major component with an average molecular size of 300 kDa in 7-day brain, containing a 245-kDa core glycoprotein and an average of three 22-kDa chondroitin sulfate chains. A 1D1 proteoglycan of approximately 180 kDa with a 150-kDa core glycoprotein is also present at 7 days, and by 2-3 weeks postnatal this becomes the major species, containing a single 32-kDa chondroitin 4-sulfate chain. The concentration of 1D1 decreases during development, from 20% of the total chondroitin sulfate proteoglycan protein (0.1 mg/g brain) at 7 days postnatal to 6% in adult brain. A 45-kDa protein which is recognized by the 8A4 monoclonal antibody to rat chondrosarcoma link protein copurifies with the 1D1 proteoglycan, which aggregates to a significant extent with hyaluronic acid. A chondroitin/keratan sulfate proteoglycan (designated 3H1) with a size of approximately 500 kDa was isolated from rat brain using monoclonal antibodies to the keratan sulfate chains. The core glycoprotein obtained after treatment of the 3H1 proteoglycan with chondroitinase ABC and endo-beta-galactosidase decreases in size from approximately 360 kDa at 7 days to approximately 280 kDa in adult brain. In 7-day brain, the proteoglycan contains three to five 25-kDa chondroitin 4-sulfate chains and three to six 8.4-kDa keratan sulfate chains, whereas the adult brain proteoglycan contains two to four chondroitin 4-sulfate chains and eight to nine keratan sulfate chains, with an average size of 10 kDa. The concentration of 3H1 increases during development from 3% of the total soluble proteoglycan protein at 7 days to 11% in adult brain, and there is a developmental decrease in the branching and/or sulfation of the keratan sulfate chains. A third monoclonal antibody (3F8) was used to isolate a approximately 500-kDa chondroitin sulfate proteoglycan comprising a 400-kDa core glycoprotein and an average of four 28-kDa chondroitin sulfate chains. In the 1D1 and 3F8 proteoglycans of 7-day brain, 20 and 33%, respectively, of the chondroitin sulfate is 6-sulfated, whereas chondroitin 4-sulfate accounts for greater than 96% of the glycosaminoglycan chains in the adult brain proteoglycans.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunochemical characterization and ultrastructural localization of chondroitin sulfates and keratan sulfate in embryonic chick bone marrow

Summary Monoclonal antibodies directed against specific carbohydrate epitopes on chondroitin 4-/dermatan sulfate, chondroitin 6-sulfate, keratan sulfate, and a monoclonal antibody directed against the hyaluronate binding region were used to characterize proteoglycans extracted from embryonic chick bone marrow. About half of the proteoglycans separate into the high density fraction on a CsCl gradient. Glycosaminoglycan-specific antibodies recognize proteoglycans from all fractions; this includes an antibody directed against keratan sulfate. Some proteoglycans, principally in the high buoyant density fraction, contain sites recognized by the antibody specific for the hyaluronate binding region. Within limits of detection, all core proteins belong to the high-molecular-weight category, with weights in excess of 212 kD. Antibodies directed against chondroitin 4-/dermatan sulfate and against keratan sulfate primarily bind to extracellular matrix material located in the extracellular spaces and to matrix elements in the pericellular regions of fibroblastic stromal cells. The antibody that recognizes chondroitin 6-sulfate binds to sites on surfaces of fibroblastic stromal cells and also to extracellular matrix material. Little or no antibody binding is detected on surfaces of granulocytic cells. These studies indicate that chondroitin sulfate and keratan sulfate chains are both present in the proteoglycan extract.     

Human corneal GlcNac 6-O-sulfotransferase and mouse intestinal GlcNac 6-O-sulfotransferase both produce keratan sulfate

Human corneal N-acetylglucosamine 6-O-sulfotransferase (hCGn6ST) has been identified by the positional candidate approach as the gene responsible for macular corneal dystrophy (MCD). Because of its high homology to carbohydrate sulfotransferases and the presence of mutations of this gene in MCD patients who lack sulfated keratan sulfate in the cornea and serum, hCGn6ST protein is thought to be a sulfotransferase that catalyzes sulfation of GlcNAc in keratan sulfate. In this report, we analyzed the enzymatic activity of hCGn6ST by expressing it in cultured cells. A lysate prepared from HeLa cells transfected with an intact form of hCGn6ST cDNA or culture medium from cells transfected with a secreted form of hCGn6ST cDNA showed an activity of transferring sulfate to C-6 of GlcNAc of synthetic oligosaccharide substrates in vitro. When hCGn6ST was expressed together with human keratan sulfate Gal-6-sulfotransferase (hKSG6ST), HeLa cells produced highly sulfated carbohydrate detected by an anti-keratan sulfate antibody 5D4. These results indicate that hCGn6ST transfers sulfate to C-6 of GlcNAc in keratan sulfate. Amino acid substitutions in hCGn6ST identical to changes resulting from missense mutations found in MCD patients abolished enzymatic activity. Moreover, mouse intestinal GlcNAc 6-O-sulfotransferase had the same activity as hCGn6ST. This observation suggests that mouse intestinal GlcNAc 6-O-sulfotransferase is the orthologue of hCGn6ST and functions as a sulfotransferase to produce keratan sulfate in the cornea.