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

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Query: EC:2.4.99.6 (sialyltransferase)
1,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The carbohydrate structure of the major oligosaccharide of human interferon-beta (IFN-beta) synthesized by a genetically engineered Chinese hamster ovary cell line has been determined. Analysis of the glycopeptidase F-released carbohydrates by sequential exoglycosidase treatment, methylation analysis, and fast atom bombardment-mass spectrometry revealed that 95% of the IFN-beta oligosaccharides had the following structure: (Formula: see text). The remaining 5% of the carbohydrates are probably tri- or higher antennary oligosaccharide chains. The major oligosaccharide of the recombinant IFN-beta is remarkably homogeneous with respect to terminal galactose sialylation. NeuAc, which is alpha 2-3-linked to galactose in the human IFN-beta secreted by Chinese hamster ovary cells, can be re-incorporated with an alpha 2-6 linkage in vitro, into enzymatically desialylated IFN-beta using rat liver Gal beta 1-4GlcNAc alpha 2-6 sialyltransferase. The sugar chain is important for maintaining protein solubility as shown by the fact that IFN-beta protein precipitates after deglycosylation with glycopeptidase F.
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PMID:Structure of the carbohydrate moiety of human interferon-beta secreted by a recombinant Chinese hamster ovary cell line. 366 93

Regenerating rat liver microsomes contain a beta-D-galactoside alpha-(2----3)- and a 2-acetamido-2-deoxy-beta-D-glucoside alpha-(2----6)-sialyltransferase that are involved in the synthesis of the terminal alpha-NeuAc-(2----3)-beta-D-Galp-(1----3)-alpha-[NeuAc-(2----6)]-beta- D-GlcpNAc-(1----R) group occurring in human milk oligosaccharides and the glycan chains of several N-glycoproteins. Analysis by liquid chromatography and methylation of the products of sialylation obtained when lacto-N-tetraose [beta-D-Galp-(1----3)-beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4) -D-Glc] was used as a substrate in the incubations in vitro indicated that the disialylated sequence is formed for greater than 95% through the tetrasaccharide alpha-NeuAc-(2----3)-beta-D-Gal-(1----3)-beta-D-GlcNAc-(1----3)-beta-D-G al- (1----4)-D-Glc as one of two possible intermediates. This indicates that in the synthesis of the disialylated sequence the alpha-(2----3)- and the alpha-(2----6)-sialyltransferase act in a highly preferred order in which the alpha-(2----3) enzyme acts first. This order is imposed by the specificity of the alpha-(2----6)-sialyltransferase, which requires an alpha-NeuAc-(2----3)-beta-D-Gal-(1----3)-beta-D-GlcNAc-(1----R) sequence for optimal activity, and shows very low and no activity with beta-D-Gal-(1----3)-beta-D-GlcNAc-(1----R) and beta-D-GlcNAc-(1----R) acceptor structures, respectively. Results obtained with normal rat, fetal calf, rabbit and human liver, and human placenta indicated that very similar or identical sialyltransferases occur in these tissues. It is suggested that these enzymes differ from the sialyltransferases that previously had been identified in fetal calf liver and human placenta.
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PMID:Biosynthesis of disialylated beta-D-galactopyranosyl-(1----3)-2-acetamido-2-deoxy-beta-D-glucopy ran osyl oligosaccharide chains. Identification of a beta-D-galactoside alpha-(2----3)- and a 2-acetamido-2-deoxy-beta-D-glucoside alpha-(2----6)-sialyltransferase in regenerating rat liver and other tissues. 373 Nov 83

Hodgkin's disease-derived giant cell lines (HD-cells) express high levels of ectosialyltransferase activity presumed to be a galactose-specific lectin recognizing the desialylated 3-fucosyl-N-acetyllactosamine structure (X-hapten). Both the anti-X-hapten monoclonal antibody VIM-D5 and a polyclonal antiserum to another galactose-lectin, the hepatic asialoglycoprotein receptor (HBP), recognize a 55,000-mol wt HD-cell protein (Paietta, E., R. J. Stockert, A. G. Morell, V. Diehl, and P. H. Weirnik. 1986. Proc. Natl. Acad. Sci. USA. 83:3451-3455.) That the expression of the 55,000-mol wt protein is restricted to HD-cells among X-hapten positive cells lines is confirmed in this study. The 55,000-mol wt protein is shown to be present on the cell surface and intracellularly, where an additional immunocrossreactive 150,000-mol wt protein is recognized. Extraction of the 55,000 mol wt protein from HD-cell lysates by affinity chromatography results in the loss of sialyltransferase activity. While evidence for a single protein possessing both the antigenic and the enzymatic activity is not direct, these results suggest that the ectosialyltransferase unique to HD-cells is a 55,000-mol wt membrane glycoprotein possessing the X-hapten oligosaccharide.
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PMID:Unique antigen of cultured Hodgkin's cells. A putative sialyltransferase. 373 96

By use of 500-MHz 1H NMR spectroscopy, the branch specificity of bovine colostrum CMP-NeuAc:Gal beta 1----4GlcNAc-R alpha 2----6-sialyltransferase towards a biantennary glycopeptide and oligosaccharides of the N-acetyllactosamine type, differing in completeness and structure of their core portion, was investigated. In agreement with earlier reports (Van den Eijnden, D. H., Joziasse, D. H., Dorland, L., Van Halbeek H., Vliegenthart, J. F. G., and Schmid, K. (1980) Biochem. Biophys. Res. Commun. 92, 839-845), it appears that the enzyme strongly prefers the galactosyl residue at the Man alpha 1----3Man branch of the biantennary glycopeptide for attachment of the first sialic acid residue. This branch specificity is fully preserved with the structure (formula; see text) Reduction of the reducing N-acetylglucosaminyl residue in this structure, however, leads to a decreased branch specificity, whereas removal of this residue results in a random attachment of sialic acid to the galactoses at both branches. The decrease in branch specificity is accompanied by a reduction in the rate of sialic acid transfer to the galactose at the alpha 1----3 branch. Our results indicate that the presence of the aforementioned N-acetylglucosaminyl residue is a minimal structural requirement for branch specificity of the sialyltransferase. We propose that in the interaction of the sialyltransferase with its substrates, this N-acetylglucosaminyl residue functions as a recognition site mediating the correct positioning of the substrate on the enzyme.
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PMID:Branch specificity of bovine colostrum CMP-sialic acid: N-acetyllactosaminide alpha 2----6-sialyltransferase. Interaction with biantennary oligosaccharides and glycopeptides of N-glycosylproteins. 388 25

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.
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PMID:Increased sialylation of complex glycopeptides during differentiation of mouse embryonal carcinoma cells. 392 74

A sialyltransferase which catalyzes the in vitro biosynthesis of N-acetylneuraminosyllacto-N-neohexaosylceramide from lacto-N-neohexaosylceramide and CMP-NeuAc has been examined in embryonic chicken breast muscle. The maximum enzyme activity was observed in 11-12-day-old embryos. The enzyme has optimum activity at pH 6.8 in the presence of Triton CF-54 and Mg2+. The apparent Km values for lacto-N-neohexaosylceramide and CMP-NeuAc were 0.9 and 0.67 mM, respectively. The enzymic product was characterized by TLC, neuraminidase hydrolysis and permethylation analysis. The structure was identical to authentic N-acetylneuraminosyllacto-N-neohexaosylceramide from chicken muscle. In addition, a disialo derivative has been detected that constitutes 15% of the total radioactivity incorporated. The two sialic acids connected by sialosyl-sialosyl linkage were attached to the terminal galactose residue. To our knowledge, this is the first report of biosynthesis of this disialo compound.
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PMID:Sialylation of lacto-N-neohexaosylceramide by sialyltransferase from embryonic chicken muscle. 395 72

A CMP-NeuAc:Gal beta 1----3GalNAc-R alpha 2----3-sialyltransferase has been purified over 20,000-fold from a Triton X-100 extract of human placenta by affinity chromatography on concanavalin A-Sepharose and CDP-hexanolamine-Sepharose in a yield of 10%. Sodium dodecyl sulfate-gel electrophoresis under reducing conditions revealed that the enzyme consists of a major polypeptide species with a molecular weight of 41,000 and some minor forms with molecular weights of 40,000, 43,000, and 65,000, respectively, which can be resolved partially by gel filtration on Sephadex G-100. Isoelectric focusing revealed that the enzyme occurs in a major and a minor charged form with pI values of 5.0-5.5 and 6.0, respectively. Acceptor specificity studies indicated that the enzyme catalyzes the incorporation of sialic acid from CMP-NeuAc into glycoproteins, glycolipids, and oligosaccharides which possess a terminal Gal beta----3GalNAc unit. Analysis of the structure of the product chain by high-pressure liquid chromatography and thin layer chromatography as well as methylation analysis revealed that a NeuAc alpha 2----3Gal beta 1----3GalNAc sequence is elaborated. The best glycoprotein acceptors are antifreeze glycoprotein and porcine submaxillary asialo/afucomucin. The disaccharide Gal beta 1----3GalNAc-Thr shows values for Km and V which are close to those of the latter glycoprotein. Lactose as well as oligosaccharides in which galactose is linked beta 1----3 or beta 1----4 to N-acetylglucosamine are less efficient acceptors. Of the glycolipids tested only gangliosides GM1 and GD1b served as an acceptor. The enzyme does not show an absolute aglycon specificity, and attaches sialic acid regardless the anomeric configuration of the N-acetylgalactosaminyl residue in the accepting Gal beta 1----3GalNAc unit. By use of specific acceptor substrates it could be demonstrated that the purified enzyme is free from other known sialyltransferase activities. Studies with rabbit antibodies raised against a partially purified sialyltransferase preparation indicated that the enzyme is immunologically unrelated to a Gal beta 1----4GlcNAc-R alpha 2----3-sialyltransferase, which previously had been identified in human placenta (Van den Eijnden, D.H., and Schiphorst, W. E. C. M. (1981) J. Biol. Chem. 256, 3159-3162). Initial-rate kinetic studies suggest that the sialyltransferase operates through a mechanism involving a ternary complex of enzyme, sugar donor, and acceptor. This is the first report on the extensive purification and characterization of a sialyltransferase from a human tissue.
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PMID:Purification and enzymatic characterization of CMP-sialic acid: beta-galactosyl1----3-N-acetylgalactosaminide alpha 2----3-sialyltransferase from human placenta. 398 39

GMP-N-Acetylneuraminate: galactosyl-glycoprotein sialytransferase (CMP-N-acetylneuraminate: D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) activity was identified in the human cervical epithelium. The enzyme has a pH optimum of 6.0, a temperature optimum of 28 degrees C, and demonstrates a partial requirement for Triton X-100. Michaelis constants for asialofetuin and CMP-N-acetyl[14C]neuraminic acid are 0.64 . 10(-5) M (expressed as the concentration of terminal galactose residues) and 2.05 . 10(-5) M, respectively. Sialytransferase demonstrated minimal affinity for the low molecular weight acceptors tested, and may have a requirement for a glycoprotein acceptor having a terminal N-acetyllactosamine (Gal beta (1 leads to 4)GlcNAc) type structure. Cytidine nucleotides are potent inhibitors of the sialyltransferase reaction; CMP acts as a competitive inhibitor.
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PMID:Glycosyltransferases of the human cervical epithelium. II. Characterization of a CMP-N-acetylneuraminate: galactosyl-glycoprotein sialyltransferase. 616 92

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.
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PMID:Compartmentation of asparagine-linked oligosaccharide processing in the Golgi apparatus. 622 41

Lines of KB cells resistant to Sendai virus-induced cytolysis have been isolated and characterized (Toyama, S., Toyama, Su., and Uetake, H. (1977) Virology 76, 503-515). This study is concerned with the nature of this mutation. Plasma membrane fractions from Sil cells were found to have decreased amount of sialic acid and the same amount of galactose as compared to the membranes from parental KB cells. Sil cells exhibited an increase in sensitivity to toxic effects of ricin and a decrease in sensitivity to wheat germ agglutinin. Binding of wheat germ agglutinin to Sil cells was markedly decreased. Several membrane glycoproteins of Sil cells migrated slightly faster than the corresponding bands of wild type membrane when examined by gel electrophoresis in sodium dodecyl sulfate. Sil cells had decreased sialyltransferase activity that catalyzed the transfer of sialic acid residues from CMP-N-acetylneuraminic acid to glycoprotein acceptors containing Gal beta 1 leads to 3GalNAc alpha 1 leads to O-Ser(Thr) chain. The decreased enzyme activity could not be accounted for by the presence of inhibitors, altered pH optimum, or increased sialidase or CMP-sialic acid hydrolase activities. These results indicate that a molecular basis for the Sil cell phenotype might be the deficiency of sialyltransferase.
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PMID:Deficient cytidine monophospho-N-acetylneuraminic acid: glycoprotein sialyltransferase activity in a clone of KB cells with altered cell fusion ability. 640 1


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