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Query: EC:3.1.6.4 (chondroitinase)
 2,039 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied a glucuronyltransferase involved in chondroitin sulfate (CS) biosynthesis in a preparation obtained from fetal bovine serum by heparin-Sepharose affinity chromatography. This enzyme transferred GlcA from UDP-GlcA to the nonreducing GalNAc residues of polymeric chondroitin. It required Mn2+ for maximal activity and showed a sharp pH optimum between pH 5.5 and 6.0. The apparent Km value of the glucuronyltransferase for UDP-GlcA was 51 microM. The specificity was investigated using structurally defined acceptor substrates, which consisted of chemically synthesized tri-, penta-, and heptasaccharide-serines and various odd-numbered oligosaccharides with a GalNAc residue at the nonreducing terminus, prepared from chondroitin and CS by chondroitinase ABC digestion followed by mercuric acetate treatment. The enzyme utilized a heptasaccharide-serine GalNAc beta 1-4GlcA beta 1-3GalNAc beta 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser and a pentasaccharide-serine GalNAc beta 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser as acceptors. In contrast, neither a trisaccharide-serine Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser nor an alpha-GalNAc-capped pentasaccharide-serine GalNAc alpha 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser that is a model compound of the reaction product formed by the action of the alpha-GalNAc transferase recently demonstrated in fetal bovine serum (Kitagawa et al., J. Biol. Chem., 270, 22190-22195, 1995) was utilized as an acceptor. Besides, all nonsulfated odd-numbered oligosaccharides except for the trisaccharide GalNAc beta 1-4GlcA beta 1-3GalNAc served as acceptors and the transfer rates roughly increased with increasing chain length. Moreover, 6-O-sulfation of nonreducing terminal GalNAc markedly enhanced GlcA transfer, whereas 4-O-sulfation had little effect on it. These results indicated that at least two glucuronyltransferases are involved in the biosynthesis of CS and that sulfation reactions may play important roles in chain elongation.
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PMID:Characterization of serum beta-glucuronyltransferase involved in chondroitin sulfate biosynthesis. 936 32

We recently reported that the heparin (Hep) III domain of fibronectin contains the H2 cell adhesion site in repeat III5 which binds activated alpha4 integrins. We have now further characterized the heparin and cell binding activities of this domain. A recombinant fragment containing repeats III4-III5 (FN-III4-5) induced Jurkat cell adhesion upon integrin activation with Mn2+ or TS2/16 monoclonal antibody (anti-beta1). Adhesion of Mn2+-treated cells to FN-III4-5 or FN-III5 fragments was inhibited by chondroitinase ABC and ACII but not by the anti-alpha4 monoclonal antibody HP2/1. In contrast, HP2/1 completely blocked adhesion of TS2/16-treated cells while chondroitinase had a partial (FN-III4-5) or minor (FN-III5) effect. Thus, the role of each receptor depended on the stimulus used to activate alpha4 beta1. The combination of HP2/1 and chondroitinase at dilutions which did not inhibit when used individually abolished adhesion of Mn2+ or TS2/16-treated cells to both fragments, indicating a cooperative effect between alpha4beta1 and chondroitin sulfate proteoglycans (CSPG). Furthermore, we have identified a 20-amino acid sequence in III5 (HBP/III5) which binds heparin and induces cell adhesion via CSPG exclusively. Although soluble HBP/III5 was a poor inhibitor, when combined with H2, it abolished adhesion to FN-III4-5 and FN-III5 fragments. These results establish that adhesion to the Hep III domain involves the cooperation of activated alpha4 beta1 and CSPG and show that HBP/III5 is a novel heparin and CSPG-binding site contributing to cell adhesion to this domain.
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PMID:Cooperative role for activated alpha4 beta1 integrin and chondroitin sulfate proteoglycans in cell adhesion to the heparin III domain of fibronectin. Identification of a novel heparin and cell binding sequence in repeat III5. 986 21