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)

1. Cytidine-5'-monophospho-N-acetylneuraminic acid: (galactosyl-N-acetyl-galactosaminyl-(N-acetylneuraminyl)-galactosyl-glucosylceramide sialyltransferase (CMP-NAcNeu: monosialoganglioside (GM1) sialyltransferase) activity was demonstrated in the neurohypophysis of the rabbit. 2. Optimum activity occurred at pH 6.5 and required the presence of exogenous galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosyl-glucosylceramide (GM1 ganglioside), detergent (Triton X-100), and divalent cation (Mn2+, Mg2+ or Ca2+). 3. The product of the reaction was characterized as N-acetylneuraminyl-galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosyl-glucosylceramide (GD1a) by ascending thin-layer chromatography. 4. Physiological stimulation of vasopressin secretion, by the substitution of 2.2% NaCl for drinking water for 14 days, had no effect on the enzyme activiity or the ganglioside content of the tissue.
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PMID:Cytidine-5'-monophospho-N-acetylneuraminic acid galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosyl-glucosylceramide sialyltransferase in the neurohypophysis of the rabbit. 0 25

A cell-free system was established to study the biosynthesis of group C meningococcal capsular polysaccharide, an alpha-2 leads to 9-linked N-acetylneuraminic acid (NeuAc) homopolymer containing O-acetyl groups at either C7 or C8. Sialyltransferase activity, isolated from group C meningococcus strain C-11, catalyzed incorporation of [14C]NeuAc from CMP (CMP--[14C]NeuAc) into polymeric form. This sialyltransferase was stimulated by addition of meningococcus group C and Escherichia coli K92 capsular polysaccharides, the latter being an alpha-2 leads to 8- and alpha-2 leads to 9-linked NeuAc heteropolymer. Group C meningococcal sialyltransferase did not require divalent ions but was stimulated by Mn2+. Attempts to demonstrate a lipid-soluble intermediate in the biosynthesis of this NeuAc polymer were unsuccessful. Meningococcal group C sialyltransferase incorporated NeuAc into a membrane-associated product. The polysaccharide can be extracted from the membrane-bound fraction with Triton X-100. The newly synthesized polysaccharide coprecipitates with authentic group C antigen in meningococcal group C antiserum and is degraded by sodium metaperiodate, indicating that the NeuAc polymer synthesized by the cell-free system consists of alpha-2 leads to 9 linkage. Meningococcal group C spheroplast membranes contain an O-acetylase that can catalyze the transfer of acetyl groups from acetyl coenzyme A to the in vitro-synthesized polysaccharide.
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PMID:Cell-free biosynthesis of the O-acetylated N-acetylneuraminic acid capsular polysaccharide of group C meningococci. 2 63

A sialyltransferase (CMP-N-acetylneuraminate:D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) which attaches N-acetylneuraminic acid to the terminal end of the carbohydrate chain of kappa-casein was found to be concentrated in Golgi apparatus-enriched fractions of bovine mammary gland. Maximum sialyltransferase activity was obtained at pH 5.5 and 37 degrees C in the presence of 1 mM dithiothreitol and Triton X-100. A Km of 0.19 mg asialo-kappa-casein/ml (0.01 mM) was obtained for the sialyltransferase. Native kappa-casein also served as acceptor for N-acetylneuraminic acid transferase of Golgi apparatus-enriched fractions although at a slower rate than did asialo-kappa-casein. The sialyltransferase has a divalent cation requirement for maximum activity which was best satisfied by the presence of 10 mM Mn2+.
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PMID:Glycosylation of kappa-casein. I. Localization and characterization of sialyltransferase in bovine mammary gland. 3 13

1. The rainbow trout (Oncorhynchus mykiss) CMPNeuAc:lactosylceramide alpha 2----3sialytransferase enzyme from RTH-149 cells has been characterized. 2. Transfer of sialic acid to lactosylceramide was optimal at a pH of 5.9, temperature of 25 degrees C, and in the pressure of 0.3% CF-54, 10 mM Mn2+, 0.1 M sodium cacodylate, and 2 mM ATP. 3. Golgi-rich membrane fractions of RTH-149 cells were found to be enriched in sialidase activity and as such the addition of 40 microM 2,3-dehydro-2-deoxy-N-acetylneuraminic acid was necessary to assay alpha 2----3sialyltransferase activity optimally. 4. Apparent Km for donor (CMPNeuAc) and acceptor (lactosylceramide) were found to be 243 microM and 34 microM, respectively. 5. The alpha 2----3sialyltransferase characterized was found to be primarily specific for lactosylceramide though minor activity with other glycolipid acceptors was observed. 6. The presence of another sialyltransferase with differing substrate specificity was noted. 7. Properties of this enzyme, compared to analogous mammalian enzymes, are discussed.
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PMID:Characterization of a CMPNeuAc: lactosylceramide alpha 2----3sialyltransferase from rainbow trout hepatoma (RTH-149) cells. 206 Feb 83

The main aim of our study was to investigate whether the marked decrease in the expression of peanut agglutinin (PNA) receptors during T-cell maturation in the mouse is accompanied by increased activity of sialyltransferase. By differential agglutination with PNA, mature thymocytes (PNA-) were separated from immature ones (PNA+) and the separated fractions were tested for their sialyltransferase activity with asialofetuin as acceptor. In parallel, sialyltransferase activities of hydrocortisone-resistant thymocytes and untreated thymocytes were also compared. Optimization of the enzyme assay revealed that previous results in the literature were obtained under suboptimal conditions. Using manganese chloride instead of magnesium chloride, we have now found that hydrocortisone-resistant thymocytes contain 3.3-fold more sialyltransferase activity compared to untreated thymocytes. PNA- thymocytes contain 8.1-fold more enzyme activity compared to the PNA+ cells. Studies with fluorescein conjugated PNA of the agglutinated and unagglutinated thymocyte fractions suggest that the trace amount of sialyltransferase activity found in the PNA+ fraction may result from 5 to 10% cross-contamination with PNA- cells. These results suggest that the cellular levels of sialyltransferase specific for asialofetuin may play an important role in T-cell differentiation.
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PMID:Changes in sialyltransferase activity during murine T cell differentiation. 348 16

The existence of a brain sialyltransferase catalyzing the specific transfer of NeuAc on native fetuin was demonstrated. This enzyme was not able to sialylate either asialofetuin or desialylated and nondesialylated orosomucoid, transferrin, and bovine submaxillary mucin. It required the presence of Mn2+ for optimal activity. Moreover, in fetuin, this activity was closely related to the proportion of NeuAc residues, but in liver tissue sialylation occurred only onto asialofetuin. In native fetuin, sialylation took place on O-glycan chains to give an O-disialyltetrasaccharidic structure. The Gal----GalNAc----protein was not an acceptor, but alpha-NeuAc-(2----3)-Gal----GalNAc----protein was, suggesting a specific transfer alpha-(2----6) to the GalNAc residue.
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PMID:A brain sialyltransferase having a narrow specificity for O-glycosyl-linked oligosaccharide chains. 373 Nov 79

Some properties of the sialyltransferase activity of homogenates prepared from normal human platelets were investigated using asialo-fetuin as substrate. The enzyme activity was optimal at pH 6.5 and was stimulated by divalent cations in the order Mg2+ greater than Mn2+ greater than Ca2+. Buffers of high ionic strength strongly reduced the activity. ATP and ADP were not inhibitors at 0.1 mM concentration, but AMP, CTP and CMP reduced the activity by 15-30%. A native endogenous acceptor for the enzyme activity was located in the platelet homogenates. The range of fetuin-sialyltransferase activity found in platelets isolated from 6 normal donors was 79 +/- 39 pmol/h/mg protein (mean +/- SD). The platelets of patients with Glanzmann's thrombasthenia and the Bernard-Soulier syndrome, which are characterized by different membrane glycoprotein deficiencies, were shown to have fetuin-sialyltransferase activities within the normal range indicating that the membrane glycoprotein defects in the platelets of these patients are not associated with the absence of sialyltransferase activity.
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PMID:Glycoprotein-sialyltransferase activity of normal human, thrombasthenic and Bernard-Soulier platelets. 616 43

Highly purified rat brain myelin isolated by two different procedures showed appreciable activity for CDP-ethanolamine: 1,2-diacyl-sn-glycerol ethanolaminephosphotransferase (EC 2.7.8.1). Specific activity was close to that of total homogenate and approximately 12-16% that of brain microsomes. Three other lipid-synthesizing enzymes, cerebroside sulfotransferase, lactosylceramide sialyltransferase, and serine phospholipid exchange enzyme, were found to have less than 0.5% the specific activity in myelin compared with microsomes. Washing the myelin with buffered salt or taurocholate did not remove the phosphotransferase, but activity was lost from both myelin and microsomes by treatment with Triton X-100. It resembled the microsomal enzyme in having a pH optimum of 8.5 and a requirement for Mn2+ and detergent, but differed in showing no enhancement with EGTA. The diolein Km was similar for the two membranes (2.5-4 x 10(-4) M), but the CDP-ethanolamine Km was lower for myelin (3-4 x 10(-5) M) than for microsomes (11 - 13 x 10(-5 M). Evidence is reviewed that this enzyme is able to utilize substrate from the axon in situ.
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PMID:Evidence for the presence of CDP-ethanolamine: 1,2-diacyl-sn-glycerol ethanolaminephosphotransferase in rat central nervous system myelin. 625 94

A sialyltransferase activity which catalyzes the synthesis of the trisialoganglioside GT1a from added disialoganglioside TD1a and CMP-N-acetylneuraminic acid has been demonstrated using a particulate fraction of 9-day-old embryonic chick brains. The enzyme exhibited optimum activity with the detergent Triton CF-54 and showed a broad pH optimum of 6.0 to 7.2. Ca2+ inhibited the reaction, whereas Mn2+, Mg2+, and EDTA had no effect. Slight elevations in activity were seen in the presence of Hg2+ or histone. The apparent Km for GD1a leading to GT1a was estimated to be 10(-3) M. When the monosialoganglioside, GM1, was used as the glycolipid substrate under conditions optimum for the synthesis of GR1a from GD1a, approximately 65% of the radioactive label was found in GD1a. However, about 50% of the remaining radioactivity was found in GT1a. The results suggest that the synthesis of GR1a could proceed via the sequence GM1 yields GD1a yields GT1a.
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PMID:In vitro biosynthesis of an isomer of brain trisialoganglioside, GT1a. 676 28

Golgi vesicles were isolated and purified from rat liver, in which the specific activities of glycosyltransferases (e.g. GM3:CMP-NeuAc sialyltransferase, GD3 synthase; GM3:UDP-GalNAc galactosaminyltransferase, GM2 synthase) were 50-60-times enriched relative to microsomes or total homogenate. Synthesis of gangliosides GM2 and GM1 in such Golgi vesicles is, in the absence of any detergents, stimulated 6-fold and 20-fold respectively by phosphatidylglycerol. Other phospholipids like phosphatidylethanolamine and phosphatidylserine are also significantly stimulatory. With 50 micrograms Golgi protein and 1 nmol UDP-GalNAc, optimal stimulation of GM2 synthase was obtained with 20 micrograms of phosphatidylglycerol and 7.5 nmol of the lipid acceptor GM3. Under the same experimental conditions this stimulation exceeds (by about 40%) that obtained with optimal amount (200 micrograms) of the detergent octylglucoside. Phosphatidylglycerol, on the other hand, has virtually no stimulatory activity on the synthesis of ganglioside GD3 either in the presence of Mg2+ or Mn2+, indicating that facilitation by phospholipid of GM3 transport into Golgi vesicles was not the basis of stimulation of GM2 synthesis. Tunicamycin inhibits the synthesis of gangliosides GM2 and GM1 in isolated Golgi vesicles, but only in the absence of detergents. In the presence of phosphatidylglycerol, GM2 synthesis, for example, was inhibited by 60% by 2 micrograms tunicamycin and more than 85% by 10 micrograms tunicamycin, per 50 micrograms Golgi membrane protein. The inhibition was stronger on GM1 synthesis: 85% with 2.5 micrograms of the antibiotic. The dependence on phosphatidylglycerol and the degree of inhibition by tunicamycin of the synthetic activities are strictly dependent on the intactness of the Golgi vesicles: both phenomena become increasingly less evident when the vesicles are pelleted, and frozen and thawed several times, and completely disappear when the vesicles are solubilized by detergents or disrupted by ultrasonication. Furthermore, tunicamycin inhibition is reversible by increased concentration of phosphatidylglycerol. All these results indicate that phosphatidylglycerol does not stimulate, and tunicamycin does not inhibit, the transferases themselves; rather, the two opposing effects might relate to carrier-mediated transport, e.g. of nucleotide sugars, across Golgi vesicles.
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PMID:Ganglioside biosynthesis in Golgi apparatus of rat liver. Stimulation by phosphatidylglycerol and inhibition by tunicamycin. 686 62


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