| 1. |
- Bourgeois, C, et al.
(författare)
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Heparin-like structures on respiratory syncytial virus are involved in its infectivity in vitro.
- 1998
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Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 72:9, s. 7221-7227
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Tidskriftsartikel (refereegranskat)abstract
- Addition of heparin to the virus culture inhibited syncytial plaque formation due to respiratory syncytial virus (RSV). Moreover, pretreatment of the virus with heparinase or an inhibitor of heparin, protamine, greatly reduced virus infectivity. Two anti-heparan sulfate antibodies stained RSV-infected cells, but not noninfected cells, by immunofluorescence. One of the antibodies was capable of neutralizing RSV infection in vitro. These results prove that heparin-like structures identified on RSV play a major role in early stages of infection. The RSV G protein is the attachment protein. Both anti-heparan sulfate antibodies specifically bound to this protein. Enzymatic digestion of polysaccharides in the G protein reduced the binding, which indicates that heparin-like structures are on the G protein. Such oligosaccharides may therefore participate in the attachment of the virus.
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| 2. |
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| 3. |
- Gustafson, Stefan, et al.
(författare)
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Accessible hyaluronan receptors identical to ICAM-1 in mouse mast-cell tumours
- 1995
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Ingår i: Glycoconjugate Journal. - 0282-0080 .- 1573-4986. ; 12:3, s. 350-355
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Tidskriftsartikel (refereegranskat)abstract
- Immunohistochemical studies of the hyaluronan (HA)-receptor (R), originally found on liver endothelial cells (LEC) and related to the intercellular adhesion molecule 1 (ICAM-1), showed that polyclonal antibodies against HARLEC (HA receptor on LEC) also stain structures in mouse mastocytomas, mainly vessels. To test if intravenously administered HA might target the tumour receptors in vivo, mice carrying an inoculated mastocytoma in one hind leg muscle were injected in the tail vein with 125I-tyrosine (T)-labelled HA and killed 75 min after injection when organs and tissues were checked for radioactivity. When doses exceeding the binding capacity of the liver were injected, a significant increase in radioactivity (up to five-fold) within the tumour tissue was found. The weight adjusted difference between control and tumour tissue was greater for smaller tumours, probably due to necrosis in the larger. HA-staining of tumours from animals receiving 125I-T-HA, showed HA in areas that also stained weakly for ICAM-1 using monoclonal antibodies. ICAM-1 staining was dramatically increased after hyaluronidase treatment of the sections, indicating that the HA is bound to these receptors and thereby blocks antibody recognition.
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| 4. |
- Hodson, N, et al.
(författare)
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Identification that KfiA, a protein essential for the biosynthesis of the Escherichia coli K5 capsular polysaccharide, is an alpha -UDP-GlcNAcglycosyltransferase : The formation of a membrane-associated K5 biosynthetic complex requires KfiA, KfiB and KfiC.
- 2000
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 275:35, s. 27311-27315
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Tidskriftsartikel (refereegranskat)abstract
- The Escherichia coli K5 capsular polysaccharide consists of the repeat structure -4)GlcA-beta(1,4)-GlcNAc-alpha(1-and requires the KfiA, KfiB, KfiC, and KfiD proteins for its synthesis, Previously, the KfiC protein was shown to be a beta-UDP-GlcA glycosyltransferase, and KfiD was shown to be a UDP-Glc dehydrogenase. Here, we demonstrate that KfiA is an alpha-UDP-GlcNAc glycosyltransferase and that biosynthesis of the K5 polysaccharide involves the concerted action of the KfiA and KfiC proteins. By site-directed mutagenesis, we determined that the acidic motif of DDD, which is conserved between the C family of glycosyltransferases, is essential for the enzymatic activity of KfiA III addition, by Western blot analysis, we determined that association of KfiA with the cytoplasmic membrane requires KfiC but not KfiB, whereas the interaction of KfiC with the cytoplasmic membrane was dependent on both KfiA and KfiB. Likewise, KfiB was only detectable in cytoplasmic membrane fractions when both KfiA and KfiC were present. These data suggest that the interaction between the KfiA, KfiB, and KfiC proteins is essential for the stable association of these proteins with the cytoplasmic membrane and the biosynthesis of the K5 polysaccharide.
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| 5. |
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| 6. |
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| 7. |
- Kitagawa, H, et al.
(författare)
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N-acetylgalactosamine (GalNAc) transfer to the common carbohydrate-protein linkage region of sulfated glycosaminoglycans : identification of UDP-GaINAc:chondro oligosaccharide aNacetylgalactosaminyltransferase in fetal bovine serum
- 1995
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Ingår i: The Journal of Biological Chemsitry. - 0021-9258. ; 270:38, s. 22190-22195
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Tidskriftsartikel (refereegranskat)abstract
- During the course of a study to elucidate the role ofmodification of the common polysaccharide-protein linkagestructure, GlcAb1–3Galb1–3Galb1–4Xylb1-O-Ser, inbiosynthetic sorting mechanisms of the different sulfatedglycosaminoglycan chains, a novel N-acetylgalactosamine(GalNAc) transferase was discovered in fetalbovine serum. The enzyme catalyzed the transfer of[3H]GalNAc from UDP-[3H]GalNAc to linkage tetrasaccharideand hexasaccharide serines synthesized chemicallyand to various regular oligosaccharides containingterminal D-glucuronic acid (GlcA), which were preparedfrom chondroitin and chondroitin sulfate using testicularhyaluronidase digestion. The labeled products obtainedwith the linkage tetra- and hexasaccharideserines and with the tetrasaccharide (GlcAb1–3GalNAc)2were resistant to digestion with chondroitinase AC-IIand b-N-acetylhexosaminidase but sensitive to a-Nacetylgalactosaminidasedigestion, indicating that theenzyme is an a-N-acetylgalactosaminyltransferase. Thisfinding 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 correspondingproduct was susceptible to digestion with b-Nacetylhexosaminidase.The presence of a sulfate groupat C4 of the penultimate GalNAc or Gal units markedlyinhibited the transfer of GalNAc to the terminal GlcA,while a sulfate group at C6 of the GalNAc had little effecton the transfer. Moreover, a slight but significant transferof [3H]GalNAc was observed to an oligosaccharidecontaining terminal 2-O-sulfated GlcA as acceptor,whereas no incorporation was detected into oligosaccharidescontaining terminal unsaturated or 3-O-sulfatedGlcA units. These results suggest that this novelserum enzyme is a UDP-GalNAc:chondro-oligosaccharidea1–3- or 1–4-N-acetylgalactosaminyltransferase.
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| 8. |
- Lidholt, Kerstin, et al.
(författare)
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Assessment of glycosaminoglycan-protein linkage tetrasaccharides as acceptors for GalNAc- and GlcNAc-transferases from mouse mastocytoma.
- 1997
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Ingår i: Glycoconjugate Journal. - 0282-0080 .- 1573-4986. ; 14:6, s. 737-742
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Tidskriftsartikel (refereegranskat)abstract
- Two glycosaminoglycan-protein linkage tetrasaccharide-serine compounds, GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser and GlcA beta 1-3Gal(4-O-sulfate)beta 1-3Gal beta 1-4Xyl beta 1-O-Ser, were tested as hexosamine accepters, using UDP-[H-3]GlcNAc and UDP-[H-3]GalNAc as sugar donors, and solubilized mouse mastocytoma microsomes as enzyme source. The nonsulfated Ser-tetrasaccharide was found to function as an acceptor for a GalNAc residue, whereas the Ser-tetrasaccharide containing a sulfated galactose unit was inactive. Characterization of the radio-labelled product by digestion with alpha-N-acetylgalactosaminidase and beta-N-acetylhexosaminidase revealed that the [H-3]GalNAc unit was alpha-linked, as in the product previously synthesized using serum enzymes, and not beta-linked as found in the chondroitin sulfate polymer. Heparan sulfate/heparin biosynthesis could not be primed by either of the two linkage Ser-tetrasaccharides, since no transfer of [H-3]GlcNAc from UDP-[H-3]GlcNAc could be detected. By contrast, transfer of a [H-3]GlcNAc unit to a [GlcA beta 1-4GlcNAca1-4](2)-GlcA beta 1-4-aMan hexasaccharide acceptor used to assay the GlcNAc transferase involved in chain elongation, was readily detected. These results are in agreement with the recent proposal that two different N-acetylglucosaminyl transferases catalyse the biosynthesis of heparan sulfate. Although the mastocytoma system contains both the heparan sulfate/heparin and chondroitin sulfate biosynthetic enzymes the Ser-tetrasaccharides do not seem to fulfil the requirements to serve as accepters for the first HexNAc transfer reactions involved in the formation of these polysaccharides.
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| 9. |
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| 10. |
- Lidholt, Kerstin, et al.
(författare)
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Biosynthesis of heparin : Modulation of polysaccharide chain length in a cell-free system
- 1988
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 254:2, s. 571-578
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Tidskriftsartikel (refereegranskat)abstract
- The formation of heparin-precursor polysaccharide (N-acetylheparosan) was studied with a mouse mastocytoma microsomal fraction. Incubation of this fraction with UDP-[3H]GlcA and UDP-GlcNAc yielded labelled macromolecules that could be depolymerized, apparently to single polysaccharide chains, by alkali treatment, and thus were assumed to be proteoglycans. Label from UDP-[3H]GlcA (approx. 3 microM) is transiently incorporated into microsomal polysaccharide even in the absence of added UDP-GlcNAc, probably owing to the presence of endogenous sugar nucleotide. When the concentration of exogenous UDP-GlcNAc was increased to 25 microM the rate of incorporation of 3H increased and proteoglycans carrying polysaccharide chains with an Mr of approx. 110,000 were produced. Increasing the UDP-GlcNAc concentration to 5 mM led to an approx. 4-fold decrease in the rate of 3H incorporation and a decrease in the Mr of the resulting polysaccharide chains to approx. 6000 (predominant component). When both UDP-GlcA and UDP-GlcNAc were present at high concentrations (5 mM) the rate of polymerization and the polysaccharide chain size were again increased. The results suggest that the inhibition of polymerization observed at grossly different concentrations of the two sugar nucleotides, UDP-GlcA and UDP-GlcNAc, may be due either to interference with the transport of one of these precursors across the Golgi membrane or to competitive inhibition of one of the glycosyltransferases. The maximal rate of chain elongation obtained, under the conditions employed, was about 40 disaccharide units/min. The final length of the polysaccharide chains was directly related to the rate of the polymerization reaction.
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| 11. |
- Lidholt, Kerstin, et al.
(författare)
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Biosynthesis of the E.coli K4 capsule polysaccharide : a parallel system for studies of glycosyltransferases in chondroitin formation
- 1997
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Ingår i: The Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 272:5, s. 2682-2687
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Tidskriftsartikel (refereegranskat)abstract
- Escherichia coli K4 bacteria synthesize a capsule polysaccharide(GalNAc-GlcA(fructose))n with the carbohydratebackbone identical to chondroitin. GlcA- andGalNAc-transferase activities from the bacterial membranewere assayed with acceptors derived from thecapsule polysaccharide and radiolabeled UDP-[14C]GlcAand UDP-[3H]GalNAc, respectively. It was shown thatdefructosylated oligosaccharides (chondroitin) couldserve as substrates for both the GlcA- and the GalNActransferases.The radiolabeled products were completelydegraded with chondroitinase AC; the [14C]GlcAunit could be removed by b-D-glucuronidase, and the[3H]GalNAc could be removed by b-N-acetylhexosaminidase.A fructosylated oligosaccharide acceptor testedfor GlcA-transferase activity was found to be inactive.These results indicate that the chain elongation reactionof the K4 polysaccharide proceeds in the same wayas the polymerization of the chondroitin chain, by theaddition of the monosaccharide units one by one to thenonreducing end of the polymer. This makes the biosynthesisof the K4 polysaccharide an interesting parallelsystem for studies of chondroitin sulfate biosynthesis.In the biosynthesis of capsule polysaccharides from E.coli, a similar mechanism has earlier been demonstratedfor polysialic acid (NeuNAc)n (Rohr, T. E., and Troy, F. A.(1980) J. Biol. Chem. 255, 2332–2342) and for the K5 polysaccharide(GlcAb1–4GlcNAca1–4)n (Lidholt, K., Fjelstad,M., Jann, K., and Lindahl, U. (1994) Carbohydr. Res.255, 87–101). In contrast, chain elongation of hyaluronan(GlcAb1–3GlcNAcb1–4)n is claimed to occur at the reducingend (Prehm, P. (1983) Biochem. J. 211, 181–189).
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| 12. |
- Lidholt, Kerstin, et al.
(författare)
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Heparin proteoglycans synthesized by mouse mastocytoma contain chondroitin sulphate.
- 1995
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 311:1, s. 233-238
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Tidskriftsartikel (refereegranskat)abstract
- Proteoglycans (PGs), biosynthetically labelled with [S-35]sulphate, were isolated from mouse mastocytoma tissue. Chromatography on antithrombin (AT)-Sepharose resulted in the separation of the S-35-labelled PGs into three fractions: PGs with no affinity for the gel (NA-PGs), PGs with low affinity (LA-PGs), and PGs with high affinity (HA-PGs) for antithrombin. Whereas NA-PGs contained almost exclusively chondroitin sulphate (CS), the AT-binding PGs contained 80-85% heparin and 15-20% CS. [S-35]CS-containing macromolecules obtained from the HA-PG fraction after removal of the heparin polysaccharide chains were rechromatographed on AT-Sepharose. A majority of these S-35-labelled macromolecules no longer showed affinity for AT. These experiments indicate that the [S-35]CS recovered in the AT-binding PGs is present in hybrid PGs. Polysaccharide chain-length determination demonstrated that the heparin chains were somewhat larger (M(r) similar to 30000) than the CS chains in the NA-PGs (M(r) similar to 25000). CS chains in the hybrid PGs were slightly smaller (M(r) similar to 20000). Characterization of the sulphated CS disaccharides from NA- and HA-PGs showed that they contained similar amounts (20 %) of disulphated disaccharides of [GlcA-GalNAc(4,6-di-OSO3)] type. The monosulphated CS-disaccharides were O-sulphated at C-4 of the galactosamine units. Analysis by gel chromatography of the [S-35]CS components isolated from HA-PGs after heparinase treatment showed that a major portion of these contained one CS chain only. Calculations of the number of CS and heparin chains in AT-binding PGs, based on polysaccharide composition and polysaccharide chain length, indicate that all heparin-containing PGs are hybrids.
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| 13. |
- Lind, Thomas, et al.
(författare)
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cDNA cloning and expression of UDP-glucose dehydrogenase from bovine kidney
- 1999
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Ingår i: Glycobiology. - 0959-6658 .- 1460-2423. ; 9:6, s. 595-600
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Tidskriftsartikel (refereegranskat)abstract
- We have isolated a cDNA encoding UDP-glucose dehydrogenase from a bovine kidney cDNA-library, the first mammalian cDNA clone published. [After submission of the manuscript, a study appeared describing the molecular cloning and characterization of the human and mouse UDP-glucose dehydrogenase genes(Spicer et al., 1998).] The enzyme catalyzes the conversion of UDP-glucose to UDP-glucuronicacid, an essential precursor in glycosaminoglycan biosynthesis. The cDNA has an open reading frame of 1482 nucleotides coding for a 55 kDa protein. Expression of the enzyme in COS-7 cells showed a 3-fold increase inUDP-glucose dehydrogenase activity; also, the C-terminal 23 amino acidswas shown not to be necessary for enzyme activity. Northernblots from human and mouse tissues reveal high expression in liver and low in skeletal muscle. Human tissues have a majortranscript size of 3.2 kilobases and a minor of 2.6 whereas mousetissues have a single 2.6 kilobase transcript. We have also developed a sensitive and direct assay using UDP-[14C]Glc as a substrate for detection of small amounts of UDPGDH activity.
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| 14. |
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| 15. |
- Lind, Thomas, et al.
(författare)
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The putative tumor suppressors EXT1 and EXT2 are glycosyltransferases required for the biosynthesis of heparan sulfate
- 1998
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 273:41, s. 26265-26268
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Tidskriftsartikel (refereegranskat)abstract
- Hereditary multiple exostoses, characterized by multiple cartilaginous tumors, is ascribed to mutations at three distinct loci, denoted EXT1-3. Here, we report the purification of a protein from bovine serum that harbored the D-glucuronyl (GlcA) and N-acetyl-D-glucosaminyl (GlcNAc) transferase activities required for biosynthesis of the glycosaminoglycan, heparan sulfate (HS). This protein was identified as EXT2. Expression of EXT2 yielded a protein with both glycosyltransferase activities. Moreover, EXT1, previously found to rescue defective HS biosynthesis (McCormick, C., Leduc, Y., Martindale, D., Mattison, K., Esford, L. E., Dyer, A. P., and Tufaro, F. (1998) Nat. Genet. 19, 158-161), was shown to elevate the low GlcA and GlcNAc transferase levels of mutant cells. Thus at least two members of the EXT family of tumor suppressors encode glycosyltransferases involved in the chain elongation step of HS biosynthesis.
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| 16. |
- Roman, Elisabet, et al.
(författare)
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Overexpression of UDP-glucose dehydrogenase in Escherichia coli results in decreased biosynthesis of K5 polysaccharide
- 2003
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 374:3, s. 767-772
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Tidskriftsartikel (refereegranskat)abstract
- The Escherichia coli K5 capsular polysaccharide (glycosaminoglycan) chains are composed of the repeated disaccharide structure: -GlcAbeta1,4-GlcNAcalpha1,4-(where GlcA is glucuronic acid and GlcNAc is N-acetyl-D-glucosamine). The GlcA, present in most glycosaminoglycans, is donated from UDP-GlcA, which, in turn, is generated from UDP-glucose by the enzyme UDP-glucose dehydrogenase (UDPGDH). The formation of UDP-GlcA is critical for the biosynthesis of glycosaminoglycans. To investigate the role of UDPGDH in glycosaminoglycan biosynthesis, we used K5 polysaccharide biosynthesis as a model. E. coli was transformed with the complete gene cluster for K5 polysaccharide production. Additional transformation with an extra copy of UDPGDH resulted in an approx. 15-fold increase in the in vitro UDPGDH enzyme activity compared with the strain lacking extra UDPGDH. UDP-GlcA levels were increased 3-fold in overexpressing strains. However, metabolic labelling with [14C]glucose showed, unexpectedly, that overexpression of UDPGDH lead to decreased formation of K5 polysaccharide. No significant difference in the K5 polysaccharide chain length was observed between control and overexpressing strains, indicating that the decrease in K5-polysaccharide production most probably was due to synthesis of fewer chains. Our results suggest that K5-polysaccharide biosynthesis is strictly regulated such that increasing the amount of available UDP-GlcA results in diminished K5-polysaccharide production.
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| 17. |
- Salmivirta, Markku, et al.
(författare)
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Heparan sulfate : a piece of information.
- 1996
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Ingår i: The FASEB Journal. - 0892-6638 .- 1530-6860. ; 10:11, s. 1270-1279
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Tidskriftsartikel (refereegranskat)abstract
- The sulfated glycosaminoglycans, heparan sulfate and heparin, are increasingly implicated in cell-biological processes such as cytokine action, cell adhesion, and regulation of enzymic catalysis. These activities generally depend on interactions of the polysaccharides with proteins, mediated by distinct saccharide sequences, and expressed at various levels of specificity, selectivity, and molecular organization. The formation of heparin/heparan sulfate in the cell requires an elaborate biosynthetic machinery, that is conceived in terms of a novel model of glycosaminoglycan assembly and processive modification. Recent advances in the identification and molecular analysis of the enzymes and other proteins involved in the biosynthesis provide novel tools to study the regulation of the process, presently poorly understood, at the subcellular and cellular levels. The potential medical importance of heparin-related compounds is likely to promote the biotechnological exploitation of components of the biosynthetic machinery.
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| 18. |
- Senay, Clair, et al.
(författare)
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The EXT1/EXT2 tumor suppressors : catalytic activities and role in heparan sulfate biosynthesis
- 2000
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Ingår i: EMBO Reports. - : EMBO. - 1469-221X .- 1469-3178. ; 1:3, s. 282-286
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Tidskriftsartikel (refereegranskat)abstract
- The D-glucuronyltransferase and N-acetyl-D-glucosaminyltransferase reactions in heparan sulfate biosynthesis have been associated with two genes, EXT1 and EXT2, which are also implicated in the inherited bone disorder, multiple exostoses. Since the cell systems used to express recombinant EXT proteins synthesize endogenous heparan sulfate, and the EXT proteins tend to associate, it has not been possible to define the functional roles of the individual protein species. We therefore expressed EXT1 and EXT2 in yeast, which does not synthesize heparan sulfate. The recombinant EXT1 and EXT2 were both found to catalyze both glycosyltransferase reactions in vitro. Coexpression of the two proteins, but not mixing of separately expressed recombinant EXT1 and EXT2, yields hetero-oligomeric complexes in yeast and mammalian cells, with augmented glycosyltransferase activities. This stimulation does not depend on the membrane-bound state of the proteins.
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| 19. |
- Tsuchida, Kazunori, et al.
(författare)
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Purification and characterization of fetal bovine serum beta-N-acetyl-D-galactosaminyltransferase and beta-D-glucuronyltransferase involved in chondroitin sulfate biosynthesis
- 1999
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 264:2, s. 461-467
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Tidskriftsartikel (refereegranskat)abstract
- beta-N-Acetylgalactosaminyltransferase II and beta-glucuronyltransferase II, involved in chondroitin sulfate biosynthesis, transfer an N-acetylgalactosamine (GalNAc) and glucuronic acid (GlcA) residue, respectively, through beta-linkages to an acceptor chondroitin oligosaccharide derived from the repeating disaccharide region of chondroitin sulfate. They were copurified from fetal bovine serum approximately 2500-fold and 850-fold, respectively, by sequential chromatographies on Red A-agarose, phenyl-Sepharose, S-Sepharose and wheat germ agglutinin-agarose. Identical and inseparable chromatographic profiles of both glycosyltransferase activities obtained through the above chromatographic steps and gel filtration suggest that the purified enzyme activities are tightly coupled, which could imply a single enzyme with dual transferase activities; beta-N-acetylgalactosaminyltransferase and beta-glucuronyltransferase, reminiscent of the heparan sulfate polymerase reaction. However, when a polymerization reaction was performed in vitro with the purified serum enzyme preparation under the polymerization conditions recently developed for the chondroitin-synthesizing system, derived from human melanoma cells, each monosaccharide transfer took place, but no polymerization occurred. These results may suggest that the purified serum enzyme preparation contains both beta-N-acetylgalactosaminyltransferase II and beta-glucuronyltransferase II activities on a single polypeptide or on the respective polypeptides forming an enzyme complex, but is different from that obtained from melanoma cells in that it transfers a single GalNAc or GlcA residue but does not polymerize chondroitin.
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