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)

Six naturally occurring and three synthetic molecular species of lactosylceramide (LacCer) were used to examine the molecular species specificity of CMP-N-acetylneuraminate:lactosylceramide alpha 2,3-sialyltransferase in a Golgi-rich fraction of rat liver. The enzyme molecular species specificity was determined either in the presence of nonspecific lipid transfer protein or in the presence of detergents. Assays performed in the presence of transfer protein showed that for those lactosylceramide molecular species with either d18:1 or d18:0 long chain base the enzyme activity decreased linearly as the effective carbon number of the fatty acid increased. An increase in the carbon number of the long chain base decreased the activity of the enzyme twice as much as a corresponding increase in the carbon number of the fatty acid. On the other hand, when the enzyme activity was assayed in the presence of detergents, there was no significant difference in activity among the various molecular species of lactosylceramide based upon the carbon number of the fatty acid or on the presence of a double bond in the long chain base. However, the decrease in enzyme activity with an increase in the carbon number of the long chain base persisted. These results demonstrate that sialyltransferase has binding specificity with respect to the long chain base, but not the fatty acid. The apparent molecular species towards the fatty acid is related to the aqueous solubility of the various LacCer molecular species.
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PMID:Lactosylceramide molecular species specificity of rat liver CMP-N-acetylneuraminate:lactosylceramide sialyltransferase. 261 78

Prior studies have demonstrated that sex hormones can influence the glycosphingolipid composition of different organs, including small intestine. However, to date, the effects of testosterone on glycosphingolipids of rat small intestinal mucosa have not been examined. Experiments were conducted to examine the effect of subcutaneous administration of synthetic testosterone (500 micrograms/100 g body wt.) on the gangliosides and neutral glycosphingolipids of rat small intestinal mucosa. Their results demonstrated that testosterone administrations: (i) increased the ganglioside content including hematoside (GM3); (ii) increased the total content of neutral glycosphingolipids, which was due to the increases in glucosylceramide and globotriaosylceramide; (iii) increased the activities of cytidine 5'-monophosphate-N-acetylneuraminic acid: lactosylceramide sialyltransferase, and UDPgalactose: lactosylceramide galactosyltransferase; (iv) increased the percentage of the long chain base phytosphingosine in hematoside, glucosyl-, and globotriaosylceramide; and (v) significantly altered the fatty acid composition of each of these glycosphingolipids. These results demonstrate that administration of testosterone induces alterations in glycosphingolipid composition and glycosyltransferases activities in rat small intestinal mucosa.
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PMID:The glycosphingolipid composition and glycosyltransferase activities of the small intestinal mucosa of testosterone-treated rats. 271 26

Polysialic acid-containing glycoproteins consisting of extended chains of at least 55 sialyl residues (DP55, where DP represents degree of polymerization) are expressed on human neuroblastoma cells, CHP-134. The strategy used for detecting these unique carbohydrate structures was based on the use of two highly specific prokaryotic-derived enzyme systems and an anti-polysialosyl antibody (H.46). These probes were developed for the detection of polysialic acid on neural cell adhesion molecules (Troy, F. A., Hallenbeck, P. C., McCoy, R. D., and Vimr, E. R. (1987) Methods Enzymol. 138, 169-185). Proof for the presence of long chain multimers of sialic acid was based on two types of experiments which utilized: 1) a glycopeptide fraction of CHP-134 cells, labeled metabolically with D-[3H]GlcN and 2) a membrane fraction from CHP-134 cells which served as an exogenous acceptor of [14C] NeuNAc residues in an Escherichia coli K1 sialyltransferase assay. In vitro, this enzyme CMP-NeuNAc:poly-alpha-2,8-sialosyl sialyltransferase catalyzes the transfer of [14C]NeuNAc from CMP-[14C]NeuNAc to exogenous acceptors containing at least 3 sialyl residues. In the first series of experiments, endo-N-acetylneuraminidase (Endo-N), a bacteriophage-derived enzyme specific for hydrolyzing poly-alpha-2,8-sialosyl chains containing a minimum of 5 sialyl residues was used. Limit Endo-N digestion of the 3H-glycopeptides from the [3H] GlcN-labeled cells released short [3H]sialyl oligomers [( 3H]DP1-6) which were degraded to [3H]NeuNAc by exosialidase. Partial Endo-N digestion released a series of [3H]sialyl oligomers extending up to DP55. The longer (DP20-55) and intermediate sized (DP10-20) oligomers were isolated and converted to short oligomers ((3H]DP1-6) by retreating with Endo-N, thus confirming their identity as homo-oligomers of alpha-2,8-linked [3H]NeuNAc residues. In the second series of experiments, a membrane fraction of CHP-134 cells was radiolabeled in vitro with [14C]NeuNAc by E. coli K1 sialyltransferase. The membrane fraction had a major portion of radioactivity that was high Mr and polydisperse (Mr 100,000-250,000) as demonstrated in sodium dodecyl sulfate-polyacrylamide gels. Using Western blotting, pre-existing material of similar size was shown to react with antibody H.46.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Extended polysialic acid chains (n greater than 55) in glycoproteins from human neuroblastoma cells. 328 35

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

A glioblastoma stem cell (GSC) line, GSC11, grows as neurospheres in serum-free media supplemented with EGF (epidermal growth factor) and bFGF (basic fibroblast growth factor), and, if implanted in nude mice brains, will recapitulate high-grade glial tumors. Treatment with a STAT3 (signal transducer and activator of transcription 3) phosphorylation inhibitor (WP1193) or 10% FBS (fetal bovine serum) both led to a decrease in expression of the stem cell marker CD133 in GSC11 cells, but differed in phenotype changes. Altered glycolipid profiles were associated with some differentially expressed glycogenes. In serum treated cells, an overall increase in glycosphingolipids may be due to increased expression of ST6GALNAC2, a sialyltransferase. Serum treated cells express more phosphatidylcholine (PC), short chain sphingomyelin (SM) and unsaturated long chain phosphatidylinositol (PI). Decrease of a few glycosphingolipids in the STAT3 phosphorylation inhibited cells may be linked to decreased transcripts of ST6GALNAC2 and UGCGL2, a glucosylceramide synthase. A rare 3-sulfoglucuronylparagloboside carrying HNK1 (human natural killer-1) epitope was found expressed in the GSC11 and the phenotypically differentiated cells. Its up-regulation correlates with increased transcripts of a HNK1 biosynthesis gene, B3GAT2 after serum treatment. Taken together with a quantitative phosphoproteomic study of the same GSC line (C. L. Nilsson, et al. J. Proteome Res. 2010, 9, 430-443), this report represents the most complete systems biology study of cancer stem cell (CSC) differentiation to date. The synergies derived by the combination of glycomic, transcriptomic and phosphoproteomic data may aid our understanding of intracellular and cell-surface events associated with CSC differentiation.
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PMID:Glycomic and transcriptomic response of GSC11 glioblastoma stem cells to STAT3 phosphorylation inhibition and serum-induced differentiation. 2019 6