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

Previous studies have indicated that transfection of NIH3T3 cells with the ras oncogene induced modifications of the terminal glycosylation of N-linked glycans which appeared in the early stage after transfection. These changes affected especially the terminal part of N-linked glycans which is substituted with alpha-1,3-Gal residues in NIH3T3 and with Neu5Ac residues in the ras-transformed counterpart. We have transformed NIH3T3 cells with the human c-Ha-ras oncogene, evaluated tumorigenicity and metastatic capacity in vivo and compared alpha-1,3-galactosyltransferase, alpha-2,3- and alpha-2,6-sialyltransferases activities. By using different specific acceptors, we detected the enhancement of sialic acid transfer in transformed cells while the activity of alpha-1,3-galactosyltransferase remained unchanged. We showed that the higher sialyltransferase activity was due to the increase of beta-galactoside alpha-2,6-sialyltransferase in ras-transfectant although alpha-2,3-sialyltransferase was weakly expressed in these cells. On the basis of binding of different lectins, we correlated these observations with changes of protein glycosylation. We concluded that altered glycosylation of ras-transformed NIH3T3 is the result of a competitive effect of the enzymes acting for terminal glycosylation of N-linked glycans and the reflection of the higher expression of alpha-2,6-sialyltransferase.
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PMID:Comparison of sialyl- and alpha-1,3-galactosyltransferase activity in NIH3T3 cells transformed with ras oncogene: increased beta-galactoside alpha-2,6-sialyltransferase. 157 13

CMP-N-acetylneuraminate:lactosylceramide alpha-2,3-sialyltransferase is tightly associated with the luminal side of the Golgi membrane as is its lipid substrate, lactosylceramide. In order to understand the kinetics, properties, and regulation of this enzyme, it is necessary to alter the amount and type of substrate in the membrane while minimizing changes in the membrane environment or in the conformation of the enzyme. Therefore, nonspecific lipid transfer protein, which accelerates the transfer of phospholipids, cholesterol, and glycosphingolipids between membranes was used to study the properties and kinetics of rat liver CMP-N-acetylneuraminate:lactosylceramide sialyltransferase. These results are compared to those obtained in parallel experiments using detergent-solubilized substrate. Enzyme activity was increased four- to fivefold by transfer protein and was consistently higher than the activity measured in the presence of detergents. In contrast to the results obtained with detergents, the enzyme activity increased linearly with both Golgi protein and with incubation time for up to 60 min. The Km values for the water-soluble substrate, CMP-neuraminic acid, were virtually identical when determined in the presence of transfer protein (0.23 mM) or detergents (0.27 mM). On the other hand, the apparent Km values for the lipophilic substrate, lactosylceramide, were markedly different when determined in the presence of transfer protein (47.9 microM) or in the presence of detergents (1.2 microM). These observations suggest that transfer protein is a useful tool to study the properties and kinetics of membrane-bound enzymes when both the enzyme and substrate are components of the same membrane.
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PMID:Nonspecific lipid transfer protein in the assay of a membrane-bound enzyme CMP-N-acetyl-neuraminate:lactosylceramide sialyltransferase. 335 52

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.
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PMID:Enzymatic modeling of the oligosaccharide chains of glycoproteins immobilized onto polystyrene surfaces. 750 10

Sialyl Lewis a/sialyl Lewis x antigens, which panels of monoclonal antibodies can recognize, are synthesized by a series of glycosyltransferases. Especially, alpha (1,3)/(1,4) fucosyltransferases and/or alpha(2,3)sialyltransferases regulate expression patterns temporally and spatially, such as in epithelium of digestive systems or in leukocytes. The carbohydrate ligands of P-selectin and E-selectin have been identified as sialyl Lewis x expressed on granulocytes, monocytes, and natural killer cells. Expression of sialyl Lewis x on these cells is mainly determined by Fuc-TVII, but as for the counterparts of sialyl-transferases, there remains much uncertainty. P-selectin-dependent adhesion of tumor cells and E-selectin-dependent adhesion of tumor cells to endothelial cells play some role for tumor cell aggregation leading to microembolism and hematogenous metastasis of cancers. We have found expression of some fucosyltransferases (Fuc-TIII, VI, VII) and a sialyltransferase (ST3O) are increased in colon cancer tissues coincidentally with sialyl Lewis a antigens, with which E-selectin can interact. As already started in many laboratories, genetic manipulation of glycosylation pathways in gene-targeted animals has an outstanding potential to yield clues to oligosaccharide function.
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PMID:[Structures, synthesis and functions of sialyl Le(a)/sialyl Le(x) antigens]. 763 14

The synthesis of alpha 2,3-linked sialic acid to Gal(beta 1,3)GalNAc is mediated by at least three beta-galactoside alpha 2,3-sialyltransferases (EC 2.4.99.4, SiaT-4) that are encoded by three distinct genes. In contrast, only a single gene encodes the beta-galactoside alpha 2,6-sialyltransferase (EC 2.4.99.1, SiaT-1). This report assesses the relationship and nature of the SiaT-4 genes. Analysis of human-mouse somatic cell hybrids demonstrates that the sialyltransferase genes are dispersed in the human genome. The gene for SiaT-4 resides in chromosome 8, that for SiaT-4b resides in p21-p34 of chromosome 1 and that for SiaT-4c in q23.3-qter of chromosome 11. The gene symbols for these genes have been designated SIAT4A, SIAT4B and SIAT4C, respectively. To assess the structural organization of one of the SiaT-4 genes, a human SiaT-4a cDNA from submaxillary glands was isolated and characterized. Rapid amplification of cDNA 5' ends (5'-RACE) analysis indicates an unusually long 1 kb 5'-untranslated leader. The catalytic domain of the cloned sequence was expressed in transfected cells and was shown to be competent in mediating the specific synthesis of sialic acid alpha 2,3 to Gal(beta 1,3)GalNAc-R. Genomic sequences for SiaT-4a were also isolated and examined. The data demonstrate that coding information for SiaT-4a protein is dispersed into seven discrete exon segments in a manner reminiscent of the SiaT-1 gene. Furthermore, as in the SiaT-1 gene, intervening sequences interrupt both sialylmotif domains, regions that are conserved among all known sialyltransferases.
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PMID:Three genes that encode human beta-galactoside alpha 2,3-sialyltransferases. Structural analysis and chromosomal mapping studies. 765 69

A cDNA clone encoding chick Gal beta 1,3GalNAc alpha 2,3-sialyltransferase (ST3Gal I) was isolated from a chick embryo brain cDNA library. The cDNA sequence included an open reading frame coding for 342 amino acids, and the deduced amino acid sequence showed 64% identity with that of the mouse enzyme. Northern blot analysis of chick embryos revealed that the ST3Gal I gene was expressed in early embryonic stages. The identity of the enzyme was confirmed by construction of a recombinant sialyltransferase in which the N-terminal part including the cytoplasmic tail and signal anchor domain was replaced with an immunoglobulin signal peptide sequence. This enzyme expressed in COS-7 cells exhibited transferase activity similar to that of mouse ST3Gal I.
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PMID:Molecular cloning and expression of chick Gal beta 1,3GalNAc alpha 2,3-sialyltransferase. 776 61

We have investigated the activity of CMP-Neu5Ac:Gal beta 1-3GalNAc alpha-2,3-sialyltransferase (EC 2.4.99.4) in FR3T3 cells transformed by the Ha-ras oncogene in which we have previously demonstrated the higher expression of the beta-galactosidase alpha-2,6-sialyltransferase (EC 2.4.99.1) [21]. We demonstrate that the presence of the activated ras gene decreases the activity of this specific alpha-2,3-sialyltransferase fourfold. According to the kinetic parameters and to mixing experiments, we can assume that this decreased enzymatic activity reflects a decrease in the number of active O-glycan alpha-2,3-sialyltransferase polypeptides in ras-transformed cells. However, no change in the binding of Peanut agglutinin was observed on the cell surface of ras-transformed FR3T3 suggesting that no change in the sialylation of O-glycan core 1 appeared in these cells, although the activity of the alpha-2,3-sialyltransferase was decreased.
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PMID:Sialyltransferase activity in FR3T3 cells transformed with ras oncogene: decreased CMP-Neu5Ac:Gal beta 1-3GalNAc alpha-2,3-sialyltransferase. 835 31

The genes encoding the alpha-2,3-sialyltransferases involved in lipooligosaccharide biosynthesis from Neisseria meningitidis and Neisseria gonorrhoeae have been cloned and expressed in Escherichia coli. A high sensitivity enzyme assay using a synthetic fluorescent glycosyltransferase acceptor and capillary electrophoresis was used to screen a genomic library of N. meningitidis MC58 L3 in a "divide and conquer" strategy. The gene, denoted lst, was found on a 2. 0-kilobase fragment of DNA, and its sequence was determined and then used to design probes to amplify and subsequently clone the corresponding lst genes from N. meningitidis 406Y L3, N. meningitidis M982B L7, and N. gonorrhoeae F62. Functional sialyltransferase was produced from the genes derived from both L3 N. meningitidis strains and the N. gonorrhoeae F62. However, the N. meningitidis M982B L7 gene contained a frameshift mutation that renders it inactive. The expression of the lst gene was easily detected using the enzyme assay, and the protein expression could be detected when an immunodetection tag was added to the COOH-terminal end of the protein. Using the synthetic acceptor N-acetyllactosamine-aminophenyl-(6-(5-(fluorescein-carboxamido)-hexan oic acid amide), the alpha-2,3 specificity of the enzyme was confirmed by NMR examination of the reaction product. The enzyme could also use synthetic acceptors with lactose or galactose as the saccharide portion. This study is the first example of the cloning, expression, and examination of alpha-2,3-sialyltransferase activity from a bacterial source.
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PMID:Cloning of the lipooligosaccharide alpha-2,3-sialyltransferase from the bacterial pathogens Neisseria meningitidis and Neisseria gonorrhoeae. 891 Apr 46

The acceptor specificities of rat liver Gal(beta 1-4)GlcNAc alpha-2,6-sialyltransferase, recombinant full-length human liver Gal(beta 1-4)GlcNAc alpha-2,6-sialyltransferase, and a soluble form of recombinant rat liver Gal(beta 1-3/4)GlcNAc alpha-2,3-sialyltransferase were studied with a panel of analogues of the trisaccharide Gal(beta 1-4)GlcNAc(beta 1-2)Man(alpha 1-O)(CH2)7CH3. These analogues contain structural variants of D-galactose, modified at either C3, C4 or C5 by deoxygenation, fluorination, O-methylation, epimerization, or by the introduction of an amino group. In addition, the enantiomer of D-galactose is included. The alpha-2,6-sialyltransferases tolerated most of the modifications at the galactose residue to some extent, whereas the alpha-2,3-sialyltransferase displayed a narrower specificity. Molecular dynamics simulations were performed in order to correlate enzymatic activity to three-dimensional structure. Ineffective acceptors for rat liver alpha-2,6-sialyltransferase were shown to be inhibitory towards the enzyme; likewise, the alpha-2,3-sialyltransferase was found to be inhibited by all non-substrates. Modified sialyloligosaccharides were obtained on a milligram scale by incubation of effective acceptors with one of each of the three enzymes, and characterized by 500-MHz 1H-NMR spectroscopy.
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PMID:Exploring the substrate specificities of alpha-2,6- and alpha-2,3-sialyltransferases using synthetic acceptor analogues. 902 96

The inhibition of the alpha-2,6-sialyltransferase from rat liver, the alpha-2,3-sialyltransferase from porcine submandibular gland and of the galactosyltransferase from human milk were studied using monosaccharide-, nucleoside- and nucleotide-derivatives of their naturally occurring donor substrates cytidine 5'-monophosphate-N-acetylneuraminic acid and uridine 5'-diphosphate-galactose, respectively. Only the corresponding nucleosides/nucleotides showed inhibitory activity. Periodate oxidation of CMP or CMP-Neu5Ac and of UMP or UDP-Gal led to reduced inhibitory efficiency with the respective transferase. The type and reversibility of the inhibition of some of these compounds, as well as the corresponding Ki values were determined.
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PMID:Studies on the inhibition of sialyl- and galactosyltransferases. 907 14


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