Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.4.99.7 (sialyltransferase)
1,534 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The substrate requirements, linkage specificity, and kinetic mechanism of a pure sialyltransferase from porcine submaxillary glands have been examined. The enzyme transfers sialic acid from the donor nucleotide, CMP-NeuAc, into the sequence NeuAcalpha2 leads to 3Galbeta1 leads to 3GalNAc, which is found in both glycoproteins and gangliosides. It forms only the alpha2 leads to 3 linkage with the disaccharide Gal/beta1 leads to 3GalNAc or antifreeze glycoprotein, which, along with asialoglycoproteins containing the sequence Gal/beta1 leads to 3GalNAcalpha1 leads to O-Thr/Ser, are the best acceptor substrates. Low molecular weight galactosides linked beta1 leads to 3 to glycose residues other than N-acetylgalactosamine are poor acceptors with relatively high Km values, while those in beta1 leads to 4 or beta1 leads to 6 linkages have both high Km and low Vmax. With glycoprotein and ganglioside acceptors this substrate specificity appears to be even more strict, with the sequence Gal/beta1 leads to 3GalNAc serving as the exclusive acceptor. Thus the present enzyme is not responsible either for the sequence, NeuAcalpha2 leads to 3Galbeta1 leads to 4GlcNAc, found in the asparagine-linked chains of certain glycoproteins, or for the synthesis of hematoside, NeuAcalpha2 leads to 3Galbeta1 leads to 4Glcbeta1 leads to 1Cer. Initial rate kinetic studies, with and without inhibitors, suggest that the transferase has an equilibrium random order mechanism.
...
PMID:Enzymatic characterization of beta D-galactoside alpha2 leads to 3 sialyltransferase from porcine submaxillary gland. 43 98

Changes in the glycosylation of asparagine-linked oligosaccharides have been shown in various tumor cells, including human colon cancer. Attempts were made to elucidate the difference in Asn-linked oligo-saccharides attached to lysosomal membrane glycoproteins isolated from sublines of human colon carcinoma exhibiting high and low metastatic potentials in nude mice. Lysosomal membrane glycoproteins (lamp) 1 and 2 were immunoprecipitated from the cells after labeling with radioactive sugars, and the glycopeptides prepared were fractionated by serial lectin affinity chromatography employing immobilized concanavalin A, Datura stramonium agglutinin, and tomato lectin. Comparison of Asn-linked oligosaccharides from the different colonic carcinoma cells revealed the following features. First, the highly metastatic carcinoma cells express more poly-N-acetyllactosaminyl side chains with branched galactose residues than cells with low metastatic potential. Second, sialylation is more significant in the highly metastatic carcinoma cells than in the poorly metastatic ones. Conversely, N-acetyllactosamine units are less fucosylated in the highly metastatic cells than in poorly metastatic cells. These structural changes were apparently caused by the increase in sialyltransferase and the decrease in alpha 1----3 fucosyltransferase in the highly metastatic cells. The results also suggest that highly metastatic carcinoma cells express more sialyl Lex structures at the termini of poly-N-acetyllactosaminyl side chains than poorly metastatic carcinoma cells. Further, highly metastatic cells were found to express more lamp-1 and lamp-2 on the cell surface. These results were found to be correlated to the increased expression of sialyl Lex structures with high affinity binding of anti-sialyl Lex antibody on highly metastatic cells. Increased expression of sialyl Lex in the poly-N-acetyllactosamines of the cell surface may contribute to the metastatic behavior of the cells, assuming that this structure can serve as a better ligand for selectins present on endothelial cells and platelets.
...
PMID:Differential glycosylation and cell surface expression of lysosomal membrane glycoproteins in sublines of a human colon cancer exhibiting distinct metastatic potentials. 154 42

We investigated the glycoconjugates of the human bronchial glands at light and electron microscopic level by means of lectin histochemistry in combination with neuraminidase digestion and beta-elimination reaction. Both direct and indirect techniques using lectin-peroxidase, lectin-gold, and glycoprotein-gold complexes were applied. The binding pattern of the six lectins (ConA, HPA, DSA, WGA, LEA, and PNA) used in the present study suggests that mucous and serous cells of human bronchial glands contain both N- and O-glycosylated proteins in the secretory granules. Asparagine-linked oligosaccharides containing Gal(beta-1,4) GlcNAc and Man residues were abundant in serous cells. The demonstration of both the terminal Neu 5Ac (alpha-2,3, or 6) Gal (beta-1,4) GlcNAc sequence in the N-linked oligosaccharides of mucous cells and the terminal disaccharide Gal (beta-1,4) GlcNAc in the N-linked oligosaccharide chains of serous cells suggests the existence of complex type sugar chains N-glycosidically linked to the peptide region of the glycoproteins. The binding pattern of the DSA and the neuraminidase-DSA sequence provides evidence for the existence of sialyltransferase activity in the forming mucous granules of mucous bronchial cells.
...
PMID:Ultrastructural localization of glycoconjugates in human bronchial glands: the subcellular organization of N- and O-linked oligosaccharide chains. 155 69

The recycling of cellular glycoproteins to the site of Golgi mannosidase I, an enzyme of asparagine-linked oligosaccharide synthesis, was studied in K562 human erythroleukemia cells. Cells were metabolically labeled in the presence of deoxymannojirimycin, a reversible inhibitor of Golgi mannosidase I. This generates glycoproteins with immature oligosaccharides in their normal locations. Transport to the mannosidase I compartment was then assessed by testing for the conversion of oligosaccharides into mature forms during reculture without deoxymannojirimycin. Transferrin receptor (TfR) was acted on by mannosidase I during reculture, suggesting that it returned to the region of the Golgi complex where this enzyme resides. The slow rate of this transport (t1/2 greater than 6 h) implies that it is probably different than TfR movement during transferrin internalization (t1/2 = 10-20 min) and TfR transport to the sialyltransferase compartment in the Golgi complex (t1/2 = 2-3 h) (Snider, M. D., and O. C. Rogers, 1985, J. Cell Biol., 100:826-834). The total cell glycoprotein pool was also transported to the mannosidase I compartment with a half-time of 4 h. Because this transport is 5-10 times faster than the rate of de novo glycoprotein synthesis in these cells, it is likely that most of the glycoprotein traffic through the Golgi complex is composed of recycling molecules.
...
PMID:Membrane traffic in animal cells: cellular glycoproteins return to the site of Golgi mannosidase I. 301 99

High-molecular-weight, asparagine-linked glycopeptides--the lactosaminoglycans--are the major class of protein-bound carbohydrates synthesized by F9 cells; these cells synthesize only minor amounts of smaller glycopeptides. In contrast, F9ACC19, an endodermal cell line derived from F9 cells, synthesizes only minor amounts of lactosaminoglycans and a high proportion of smaller glycopeptides. Biochemical analysis of the small glycopeptides from F9ACC19 cells revealed that they are larger, bind less efficiently to concanavalin-A Sepharose and contain more sialic acid than their counterparts from F9 cells. Both cell types contain a small proportion of high-mannose glycopeptides. When synthesized by F9ACC19 cells, the glycopeptides of vesicular stomatitis virus show a high level of sialylation as compared to those synthesized by F9 cells, where few or no sialic-acid residues are present; this shows that the differences observed in total glycopeptides reflect differences in the glycosylation machinery of the cells. Consistent with this observation, sialyltransferase activity in vitro using a variety of acceptors was found to be markedly higher in F9ACC19 than in F9 cells, while galactosyltransferase activity was reduced several fold in F9ACC19 cells. These data support the hypothesis that the increased sialyltransferase activity in endodermal differentiated F9ACC19 cells may block the terminal galactose residue of glycopeptides, thereby inhibiting the synthesis of lactosaminoglycans in these cells.
...
PMID:Increased sialylation of complex glycopeptides during differentiation of mouse embryonal carcinoma cells. 392 74

Golgi-associated processing of complex-type oligosaccharides linked to asparagine involves the sequential action of at least six enzymes. By equilibrium sucrose density gradient centrifugation of membranes from Chinese hamster ovary cells, we have partially resolved the set of four initial enzymes in the pathway (Mannosidase I, N-acetylglucosamine (GlcNAc) Transferase I, Mannosidase II, and GlcNAc Transferase II) from two later-acting activities (galactosyltransferase and sialyltransferase). In view of the recent demonstration that galactosyltransferase is restricted to the trans face of the Golgi complex in HeLa cells (Roth, J., and E.G. Berger, 1982, J. Cell Biol., 93:223-229), our results suggest that removal of mannose and attachment of peripheral N-acetylglucosamine may occur in some or all of the remaining cisternae on the cis side of the Golgi stack.
...
PMID:Compartmentation of asparagine-linked oligosaccharide processing in the Golgi apparatus. 622 41

Rat liver Golgi was found to contain a sialyltransferase activity which would convert lacto-N-tetraose (Gal beta 1 goes to 3GlcNAc beta 1 goes to 3Gal beta 1 goes to 4Glc) to LS-tetrasaccharide a (NeuAc alpha 2 goes to 3Gal beta 1 goes to 3GlcNAc beta 1 goes to 3Gal beta 1 goes to 4Glc). The enzyme has been partially purified by affinity chromatography on CDP-hexanolamine agarose. Of the glycoprotein substrates examined, it utilizes the Gal beta 1 goes to 3GlcNAc sequence found on the asparagine-linked oligosaccharides of prothrombin as its preferred acceptor substrate, and thus has been tentatively designated a Gal beta 1 goes to 3GlcNAc alpha 2 goes to 3 sialyltransferase. The partially purified enzyme has an acceptor specificity distinct from other purified mammalian sialyltransferases which synthesize the NeuAc alpha 2 goes to 3Gal beta 1 goes to 3 GalNAc and NeuAc alpha 2 goes to 6 GalNAc sequences common to oligosaccharides O-linked to threonine or serine and the NeuAc alpha 2 goes to 6Gal beta 1 goes to 4GlcNAc sequence found on oligosaccharides N-linked to asparagine.
...
PMID:Identification of a Gal beta 1 goes to 3GlcNAc alpha 2 goes to 3 sialyltransferase in rat liver. 706 22

A method for the modification of the oligosaccharide moiety of even small amounts of purified glycoproteins by enzymatic glycosylation and deglycosylation is described. The method includes noncovalent immobilization of the glycoproteins onto the polystyrene surface of the wells of microtiter plates used as reaction tubes, deglycosylation or glycosylation by incubation either with exoglycosidases or endoglycosidases or with glycosyltransferases, and the characterization of the modified glycan structures by probing them with lectins. Placental transferrin receptor employed as a model glycoprotein was modified in amounts of as little as 100 ng removing sialic acid residues, hybrid-type glycans or all types of N-glycans with neuraminidase, endo-beta-N-acetylglucosaminidase H or peptide-N4-(acetyl-beta-glucosaminyl) asparagine amidase. Asialotransferrin receptor was alpha-2,6-sialylated with alpha-2,6-sialyltransferase from rat liver, but could not be alpha-2,3-sialylated with alpha-2,3-sialyltransferase from porcine liver. Changes in the structure and in the relative amount of the oligosaccharides could be monitored semiquantitatively with high sensitivity by the binding of digoxigenin-labeled lectins and anti-digoxigenin Fab fragments. The method is easy to use, does not require immobilization of the enzymes employed, offers simple separation of the enzymes and the product, and leaves the protein intact for further studies.
...
PMID:Enzymatic modeling of the oligosaccharide chains of glycoproteins immobilized onto polystyrene surfaces. 750 10

Linear and branched glycopeptides containing multiple sialyl-N-acetyllactosamine side chains have been synthesized using a combined chemical and enzymatic approach. Peptide backbones in which beta-GlcNAc-Asn residues were incorporated were obtained in good yields by optimized solid-phase synthesis following the Boc strategy. The resulting multivalent glycopeptides were galactosylated in near-quantitative yields using bovine galactosyltransferase, UDP-galactose, and calf alkaline phosphatase that destroys the inhibiting side product UDP. Subsequent enzymatic sialylation yielded the desired glycopeptides containing asparagine-linked sialyl-N-acetyllactosamine side chains. The compounds were characterized by 1H NMR and FABMS. Recombinant sialyltransferase and CMP-sialate synthetase were used for the enzymatic synthesis of sialosides on a preparative scale. The synthetic glycopeptides were tested as inhibitors of influenza virus to cells, revealing that most of the multivalent sialoglycopeptides exhibit increased binding that depends on the spacing when compared to monovalent compounds. A possible mechanism for increased binding is proposed.
...
PMID:Chemical and enzymatic synthesis of multivalent sialoglycopeptides. 814 76

Sialyltransferase activities, SAT-3 (CMP-NeuAc:nLcOse4Cer alpha 2-3sialyltransferase) and SAT-4 (CMP-NeuAc:GgOse4Cer alpha 2-3sialyltransferase), in Colo 205 cells catalyze the transfer of sialic acid to the terminal galactose of GlcNc-- and GalNAc-containing glycolipid substrates, respectively. Competition kinetic studies with nLcOse4Cer and GM1 as substrates in a sialyltransferase assay show that these two activities are catalyzed by two different catalytic entities. The two enzymes were co-solubilized with taurochlorate and resolved by DEAE--Cibacron Blue--Sepharose column chromatography into two elution peaks. The column eluent with SAT-3 activity failed to transfer sialic acid to asialo alpha(1)-acid glycoprotein, indicating that this enzyme is different from the sialyltransferase (ST3N) that synthesizes NeuAc alpha 2-3Gal linkage in asparagine-linked oligosaccharides of glycoprotein. However, SAT-3 activity can be immunoprecipitated with a polyclonal antibody produced against a protein expressed in Escherichia coli as GST-fusion protein from an ECB cDNA homolog of an alpha 2-3 sialyltransferase SAT-3 or STZ) the has been cloned from human melanoma cell and human placenta. Thus a concentration-dependent decrease in the residual SAT-3 activity relative to SAT-4 activity was observed in the supernatant after precipitation of the immune complex. Expression of SAT-3 (STZ) cDNA was also detected in Colo 205 cell by RT-PCR, followed by sequence analysis of the RT-PCR product. Characterization of the catalytic reaction products of SAT-3 and SAT-4 with thin-layer chromatography, sialidase treatment, and binding to specific antibodies indicates that both SAT-3 and SAT-4 catalyze the formation of alpha 2-3 linkage between sialic acid and terminal galactose of glycolipid substrates.
...
PMID:Characterization of two glycolipid: alpha 2-3sialyltransferases, SAT-3 (CMP-NeuAc:nLcOse4Cer alpha 2-3sialyltransferase) and SAT-4 (CMP-NeuAc:GgOse4Cer alpha 2-3sialyltransferase), from human colon carcinoma (Colo 205) cell line. 861


1 2 Next >>

---