Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.99.10 (sialyltransferase)
 1,547 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The assembly of most of the ceramide-linked glycolipids (GSLs) in eukaryotic cells occurs in Golgi bodies. At least 18 different glycolipid:glycosyltransferases (GSL:GLTs) have been characterized, 10 of which have been solubilized. These GLTs can be classified into 2 distinct groups: 1) GLTs dedicated to either Dol-P-P-sugar(s) or ceramide-linked sugar(s); and 2) GLTs with dual loyalties (i.e., they compete with glycolipid- and glycoprotein-bound oligosaccharides). Studies with solubilized and purified GalNAcT-1 and GalNAcT-2 from embryonic chicken brains prove that GalNAcT-1 (UDP-GalNAc:GM3 beta 1-4GalNAcT) is specific for GSL, whereas GalNAcT-2 (UDP-GalNAc:Gb3 beta 1-3GalNAcT) can transfer to an oligosaccharide containing the alpha-linked terminal galactose. Similarly, GalT-3 (UDP-Gal:GM2 beta 1-3GalT) is more specific for ganglio-oligosaccharide and GalT-4 (UDP-Gal:Lc3 beta 1-4GalT) can transfer galactose to N-acetylglucosamine linked to p-nitrophenol, glycolipid or glycoprotein. Both GalT-3 and GalT-4 have been separated and purified from embryonic chicken brains. Studies with solubilized SAT-4 and SAT-3, from bovine spleen and embryonic chicken brains, respectively, suggest the existence of 2 different gene-expressed alpha 2-3SATs. The newly discovered FucT-3 (GDP-Fuc:NeuGc-iLc6-alpha 1-3FucT) from human colon carcinoma (Colo-205) has also been solubilized and separated from other GSL:GLTs. Using a new activity gel-Western blot combined technique, the molecular mass of this FucT-3 was determined to be 105 kDa.
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PMID:Solubilized glycosyltransferases and biosynthesis in vitro of glycolipids. 314 22

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.
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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

To address the role of alpha2,8-sialyltransferase (GD3 synthase) in the biosynthesis of gangliosides, we examined the substrate specificity of the enzyme. In the ganglioside synthesis pathway, it has been generally accepted that sialyltransferase II (SAT II) catalyzes the production of GD3 from GM3, and sialyltransferase V (SAT V) catalyzes the production of GD1c/GT1a/GQ1b from GM1h/GD1a/GT1b. However, acceptor specificity of the clones GD3 synthase that was isolated from human melanoma cells [Nara, K., Watanabe, Y., Maruyama, K., Kasahara, K., Nagai. Y. & Sanai, Y. (1994) Proc. Natl Acad. Sci. USA 91, 7952-7956] has revealed that this enzyme utilized the gangliosides containing the terminal Sia(alpha2-3)Gas structure of the carbohydrate moiety, which includes GM3, GM1b, GD1a and GT1B as exogenous substrates. Kinetic data also showed that the enzyme was able to utilize both GM3 and GM1b/GD1a/GT1b as acceptor substrates. These data indicate that the enzyme catalyzes the formation of not only GD3 but also GD1c, GT1a, and GQ1B in vitro. Furthermore, by transfection of the cloned human alpha2,8-sialyltransferase cDNA, transient and stable expression of GT1a and GQ1b wa also observed in COS-7 cells and Swiss 3T3 cells that originally lacked SAT II and SAT V activities. These observations indicate that the enzyme has both SAT II and SAT V activities in vivo.
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PMID:Acceptor substrate specificity of a cloned GD3 synthase that catalyzes the biosynthesis of both GD3 and GD1c/GT1a/GQ1b. 870 63

The cDNAs encoding a new alpha2,8-sialyltransferase (ST8Sia V) were cloned from a mouse brain cDNA library by means of a polymerase chain reaction-based method using the nucleotide sequence information on mouse ST8Sia I (GD3 synthase) and mouse ST8Sia III (Siaalpha2,3Galbeta1,4GlcNAcalpha2,8-sialyltransferase ), both of which exhibit activity toward glycolipids. The predicted amino acid sequence of ST8Sia V shows 36.1% and 15.0% identity to those of mouse ST8Sia I and III, respectively. The recombinant protein A-fused ST8Sia V expressed in COS-7 cells exhibited an alpha2, 8-sialyltransferase activity toward GM1b, GD1a, GT1b, and GD3, and synthesized GD1c, GT1a, GQ1b, and GT3, respectively. The apparent Km values for GM1b, GD1a, GT1b and GD3 were 1.1, 0.082, 0.070, and 0.28 mM, respectively. However, ST8Sia V did not exhibit activity toward GM3. Thus, the substrate specificity of ST8Sia V is different from those of ST8Sia I and III, both of which exhibit activity toward GM3. Transfection of the ST8Sia V gene into COS-7 cells, which express GD1a as a major glycolipid, led to the expression of determinants for monoclonal antibody 4F10, which recognizes GT1a and GQ1b, suggesting that ST8Sia V exhibits activity toward gangliosides GD1a and/or GT1b in vivo. The expression of the ST8Sia V gene was tissue- and developmental stage-specific, and was clearly different from those of other alpha2,8-sialyltransferase genes. The ST8Sia V gene was strongly expressed in the brain and weakly in other tissues such as the liver. In addition, its expression was greater in the adult than fetal brain. These results strongly indicate that ST8Sia V is a candidate for SAT-V, the alpha2,8-sialyltransferase involved in GD1c, GT1a, GQ1b, and GT3 synthesis.
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PMID:Molecular cloning and expression of a fifth type of alpha2,8-sialyltransferase (ST8Sia V). Its substrate specificity is similar to that of SAT-V/III, which synthesize GD1c, GT1a, GQ1b and GT3. 891 Jun

The dependence of CMP-N-acetylneuraminate:GM1 sialyltransferase (SAT IV) activity of rat liver Golgi apparatus on GM1 ganglioside ceramide composition was evaluated. SAT IV activity was assayed on GM1 molecular species carrying homogeneous ceramide moieties containing long chain bases of different length (18 or 20 C atoms) unsaturated or not, linked to 14:0, 16:0, 18:0 or 22:0 fatty acids. The results obtained in the presence of the detergent Triton CF-54, when enzyme and substrate are presumably part of the same supramolecular structure, show that either the long chain base or the fatty acid composition can affect enzyme activity. This feature was not displayed when GM1 was embedded in dipalmitoylphosphatidylcholine vesicles in the absence of detergent. Under the latter conditions, the enzyme was not sensitive to the lipid composition of GM1 but to the ganglioside/phospholipid ratio in the vesicles. These results indicate for the first time that SAT IV is affected by the lipid composition of the substrate and strengthen the hypothesis that glycosyltranferases may contribute to control the cellular glycosphingolipid ceramide pattern.
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PMID:Dependence of rat liver CMP-N-acetylneuraminate:GM1 sialyltransferase (SAT IV) activity on the ceramide composition of GM1 ganglioside. 892

The alpha2,3 sialyltransferase, alpha2,3 SAT (O), catalyzes the transfer of sialic acid to Galbeta1,3 N-acetyl-D-galactosamine (GalNAc) (core-1) in mucin type O-glycosylation, and thus terminates chain extension. A Core-2 branch can also be formed from core-1 by the core-2 beta1,6 N-acetyl-d-glucosamine transferase (beta1,6 GlcNAc T) that leads to chain extension. Increased levels of the alpha2,3 SAT (O) and decreased levels of the core-2 beta1,6 GlcNAc T are seen in breast cancer cells and correlate with differences in the structure of the O-glycans synthesized (Brockhausen et al., 1995; Lloyd et al., 1996). Since in mucin type O-glycosylation sugars are added individually and sequentially in the Golgi apparatus, the position of the transferases, as well as their activity, can determine the final structure of the O-glycans synthesized. A cDNA coding for the human alpha2,3 SAT (O) tagged with an immunoreactive epitope from the myc gene has been used to map the position of the glycosyltransferase in nontumorigenic (MTSV1-7) and malignant (T47D) breast epithelial cell lines. Transfectants were analyzed for expression of the enzyme at the level of message and protein, as well as for enzymic activity. In T47D cells, which do not express core-2 beta1,6 GlcNAc T, the increased activity of the sialyltransferase correlated with increased sialylation of core-1 O-glycans on the epithelial mucin MUC1. Furthermore, in MTSV1-7 cells, which do express core-2 beta1,6 GlcNAc T, an increase in sialylated core-1 structures is accompanied by a reduction in the ratio of GlcNAc: GalNAc in the O-glycans attached to MUC1, implying a decrease in branching. Using quantitative immunoelectron microscopy, the sialyltransferase was mapped to the medial- and trans-Golgi cisternae, with some being present in the TGN. The data represent the first fine mapping of a sialyltransferase specifically active in O-glycosylation and demonstrate that the structure of O-glycans synthesized by a cell can be manipulated by transfecting with recombinant glycosyltransferases.
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PMID:A transfected sialyltransferase that is elevated in breast cancer and localizes to the medial/trans-Golgi apparatus inhibits the development of core-2-based O-glycans. 918 58

The SAT-3 activity (CMP-NeuAc:Gal beta 1-4GlcNAc beta 1-3 Gal beta 1-4Glc-ceramide alpha 2-3 sialytransferase) involved in the biosynthesis of sialy Le(x) has been characterized in human colon carcinoma cells and embryonic chicken brains. Using RT-PCR-based strategy, we have isolated partial cDNA clones of SAT-3 from ECB and Colo-205 mRNAs. Suitable primers from sialylmotif and N-terminal sequence of human placenta SAT-3 (HP-SAT-3) were used. The 800 bp cDNA fragment encoding a region (90%) of alpha 2-3 sialyltransferase (SAT-3) catalytic domain from ECB has been expressed as a glutathione S-transferase (GST) soluble fusion protein (62 kDa) in E. coli and purified over glutathione-agarose affinity matrix. Polyclonal antibody has been produced against affinity-purified catalytic domain of SAT-3 (GST-SAT-3 fusion protein). A concentration-dependent polydonal antibody binding to native SAT-3 has also been demonstrated by measuring the residual SAT-3 activity in the enzyme fractions from Colo-205. The marked inhibition (> 80%) of SAT-3 activity and relatively less inhibition (< 20%) of SAT-4 activity (CMP-NeuAc:GgOse4Cer alpha 2-3sialyl transferase) suggests strongly the existence of two different gene products (SAT-3 and SAT-4) in human colon carcinoma Colo-205 cells and in embryonic chicken brains (ECB).
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PMID:Cloning and expression of SAT-3 involved in SA-Le(x) biosynthesis: inhibition studies with polyclonal antibody against GST-SAT-3 fusion protein. 934 36

We demonstrated previously (S. Kawamura et al., Int. J. Cancer, 94: 343-347, 2001) that large amounts of ganglioside G(M3) accumulate in superficial bladder tumor, compared with invasive bladder tumors and that exogenous G(M3) inhibits the invasive potential of bladder tumor cells. To apply the G(M3) overexpression system to bladder tumor therapy, direct evidence for the important role of G(M3) in bladder tumor invasion must be obtained through transfer of the gene responsible for G(M3) overexpression. To determine the most appropriate cancer cell line for elucidating the antitumor effect of ganglioside G(M3) overexpression, the present study examined glycolipid composition, enzyme activity, and mRNA expression of the glycosyltransferases responsible for G(M3) synthesis in the bladder tumor cell lines KK-47, J82, MGH-UI, YTS-1, and MBT-2. A murine bladder carcinoma cell line (MBT-2) was transfected with a G(M3) synthase [(lactosylceramide alpha2,3-N-acetyl sialic acid transferase); sialyltransferase-I; SAT-I] cDNA, because this line does not naturally express G(M3). Stable transfectants (MBT-2-SAT-I) that overexpressed G(M3) were characterized by a reduced potential for cell proliferation, motility, invasion, and xenograft tumor growth, and an increase in the number of apoptotic cells. In the proportion of synthetic S phase, cells did not differ between MBT-2-SAT-I and mock-transfectant cells. These results suggest that the decreased proliferative potential related to G(M3) overexpression was attributable to the increased number of apoptotic cells. Although details of the mechanism of apoptosis remain unclear, the overexpression of G(M3) by gene transfer of SAT-I may present a novel therapeutic modality.
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PMID:Ganglioside G(M3) overexpression induces apoptosis and reduces malignant potential in murine bladder cancer. 1209 99

African buffalo were introduced into a wildlife conservancy in the southeast of Zimbabwe in an effortto increase the conservancy's economic viability, which is primarily based on eco-tourism. The buffalo were infected with SAT serotypes (SAT-1, SAT-2 and SAT-3) of foot and mouth disease (FMD) virus, and in order to isolate the conservancy and prevent the transmission of FMD to adjacent populations of domestic livestock, the conservancy was surrounded by a double-fence system, 1.8 m in height. The intention was to prevent the movement of both wildlife and domestic animals across the perimeter. However, two years after the buffalo were introduced, FMD occurred in cattle farmed just outside of the conservancy. Using serological and molecular diagnostic tests, epidemiological investigations showed that it was most likely that antelope (impala or kudu), infected through contact with the buffalo herd within the conservancy, had jumped over the fence and transmitted the virus to the cattle.
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PMID:An investigation into the source and spread of foot and mouth disease virus from a wildlife conservancy in Zimbabwe. 1586 73

Apoptosis of human breast carcinoma cells (SKBR-3, MCF-7, and MDA-468) has been observed after treatment of these cells with anti-cancer drug cis-platin and glycosphingolipid biosynthesis inhibitor L- and D-PPMP, respectively. These drugs initiated apoptosis in a dose-dependent manner as measured by phenotypic morphological changes, by binding of a fluorescent phophatidyl serine-specific dye (PSS-380) onto the outer leaflet of the cell membranes, and by activation of caspases, -3, -8, and -9. It was observed that in two hours very little apoptotic process had started but predominant biochemical changes occurred after 6 h. DNA degradation started after 24 hours of drug treatment. However, very little is known about the stability of the ';Replication Complexes'' during the apoptotic process. DNA helicases are motor proteins that catalyze the melting of genomic DNA during its replication, repair, and recombination processes. Previously, DNA helicase-III was characterized as a component of the replication complexes isolated from embryonic chicken brains as well as breast and colon carcinoma cells. Helicase activities were measured by a novel method (ROME assay), and DNA polymerase-alpha activities were determined by regular chain extension of the nicked ACT-DNA, by determining values obtained from +/- aphidicolin-treated incubation mixtures. In all three breast carcinoma cell lines, a common trend was observed: a decrease of activities of DNA polymerase-alpha and Helicase III. A sharp decrease of activities of the glycolipid sialyltransferases: SAT-2 (CMP-NeuAc; GD3 alpha2-8 sialyltransferase) and SAT-4 (CMP-NeuAc: GM1a alpha2-3 sialyltransferase) was observed in the apoptotic carcinoma cells treated with L-PPMP compared with cis-platin.
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PMID:Apoptosis of human breast carcinoma cells in the presence of cis-platin and L-/D-PPMP: IV. Modulation of replication complexes and glycolipid: Glycosyltransferases. 1669 1


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