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)

Two mouse L cell variant lines (CL 3 and CL 6) selected for resistance to the toxic plant lectin ricin were restricted in their ability to replicate the two alphaviruses Sindbis virus and Semliki Forest virus. CL 3 cells have been shown to exhibit increased CMP-sialic acid:glycoprotein sialyltransferase and GM3 synthetase activities, whereas CL 6 cells have been shown to contain decreased UDPgalactose:glycoprotein galactosyltransferase and UDP-N-acetylglucosamine:glycoprotein N-acetylglucosaminyltransferase activities. The adsorption of Sindbis virus to CL 6 cells was considerably reduced, suggesting that the loss or inaccessibility of the receptors for Sindbis virus accounted for a major defect in virus production in these cells. In contrast, CL 3 synthesized Sindbis viral RNA and proteins but were unable to convert the precursor glycoprotein PE2 to the structural protein E2. The cleavage of PE2 to E2 was also blocked in both CL 3 and CL 6 cells infected with Semliki Forest virus.
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PMID:Restricted replication of two alphaviruses in ricin-resistant mouse L cells with altered glycosyltransferase activities. 21 29

Four different glycolipid:glycosyltransferase activities involved in the biosynthesis in vitro of gangliosides and blood group-related glycosphingolipids have been tested in a simian virus 40-transformed glial cell culture derived from the cerebrum of a fetus with Tay-Sachs disease (TSD). The TSD cultured brain cells contained little activity of either UDP-Gal:GM2(beta 1-3)galactosyltransferase (GalT-3; EC 2.4.1.62), which catalyzes the formation of GM1a from GM2 (tay-Sachs) ganglioside, or GDP-Fuc:nLcOse4Cer (alpha 1-2)fucosyltransferase (FucT-2; EC 2.4.1.89), which catalyzes the formation of H1 glycolipid from nLcOse4Cer. These cells contained a potent inhibitor of the second reaction (catalyzed by a Golgi-rich membrane fraction from bovine spleen), whereas no inhibition of the first reaction (catalyzed by a membrane fraction from 14-day-old embryonic chicken brain) was observed. The activity of UDP-Gal:LcOse3Cer(beta 1-4)galactosyltransferase (GalT-4; EC 2.4.1.86) was 30- to 80-fold higher than the activity of GalT-3. The presence of CMP-AcNeu:nLcOse4Cer sialyltransferase activity and the absence of either GalT-3 or FucT-2 suggested a probable pathway for the synthesis of sialylneolactotetraosylceramide [GM1b(GlcNAc)] in addition to a specific blockage of GM1a ganglioside synthesis from GM2 in these TSD transformed cells.
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PMID:Differential activities of glycolipid glycosyltransferases in Tay-Sachs disease: studies in cultured cells from cerebrum. 29 63

The substrate requirements, linkage specificity, and kinetic mechanism of a pure sialyltransferase from porcine submaxillary glands have been examined. The enzyme transfers sialic acid from the donor nucleotide, CMP-NeuAc, into the sequence NeuAcalpha2 leads to 3Galbeta1 leads to 3GalNAc, which is found in both glycoproteins and gangliosides. It forms only the alpha2 leads to 3 linkage with the disaccharide Gal/beta1 leads to 3GalNAc or antifreeze glycoprotein, which, along with asialoglycoproteins containing the sequence Gal/beta1 leads to 3GalNAcalpha1 leads to O-Thr/Ser, are the best acceptor substrates. Low molecular weight galactosides linked beta1 leads to 3 to glycose residues other than N-acetylgalactosamine are poor acceptors with relatively high Km values, while those in beta1 leads to 4 or beta1 leads to 6 linkages have both high Km and low Vmax. With glycoprotein and ganglioside acceptors this substrate specificity appears to be even more strict, with the sequence Gal/beta1 leads to 3GalNAc serving as the exclusive acceptor. Thus the present enzyme is not responsible either for the sequence, NeuAcalpha2 leads to 3Galbeta1 leads to 4GlcNAc, found in the asparagine-linked chains of certain glycoproteins, or for the synthesis of hematoside, NeuAcalpha2 leads to 3Galbeta1 leads to 4Glcbeta1 leads to 1Cer. Initial rate kinetic studies, with and without inhibitors, suggest that the transferase has an equilibrium random order mechanism.
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PMID:Enzymatic characterization of beta D-galactoside alpha2 leads to 3 sialyltransferase from porcine submaxillary gland. 43 98

An inhibitory effect due to broken cells is observed when sialyltransferase (CMP-N-acetylneuraminate:D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) is measured with mixture of intact and homogenized lymphocytes. This intracellular inhibitory factor ib purified and characterized as CMP-N-acetylneuraminic acid (CMP-NeuNAc) by its behavior in various chromatographic and electrophoretic systems and by its susceptibility to CMP-NeuNAc hydrolase. This endogenous CMP-NeuNAc leads to an isotopic dilution of the exogenous labelled CMP-NeuNAc explaining the apparently lower activity of homogenate when compared to whole cells. Consequently, the radioactivity bound to acceptors may not be related to a known number of sialyl residues transferred, calling into question the validity of comparing the incorporation of [14C]NeuNAc by homogenate and whole cells in order to assign sialyltransferase activity to ectoenzyme. A new approach is developed to detect ectoglycosyltransferases with whole cells, taking into account that both intracellular enzymes and endogenous precursor may be introduced by the small percentage of broken cells.
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PMID:Detection of ectosiallyltransferase activity using whole cells. Correction of misleading results due to the release of intracellular CMP-N-acetylneuraminic acid. 48 88

The effect of butyrate on glycolipid metabolism and morphological differentiation in the cell culture system of rat ascites hepatomas, AH 7974 of island-forming type and AH 7974F of free type, was studied. Both cell lines adhered to the substratum in the presence of 1 mM butyrate. In the case of AH 7974, the addition of butyrate induced a distinct morphological change but the other cell line showed no such conspicuous change. Butyrate-treated AH 7974 cells showed a 2 to 3-fold elevation of CMP-N-acetylneuraminic acid: lactosylceramide sialyltransferase activity to form N-acetylneuraminylgalactosylglucosylceramide (GM3). On the other hand, no enzyme activity could be detected in AH 7974F cells. Four glycosyltransferase activities involved in glycolipid synthesis, including sialyltransferase in AH 7974F cells, were reduced by butyrate. From these observations we concluded that sialyltransferase to form GM3, or TM3 itself, is prerequisite for the morphological alteration induced by butyrate.
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PMID:Effect of butyrate on glycolipid metabolism of two cell types of rat ascites hepatomas with different ganglioside biosynthesis. 52 38

UDP-galactose: glycoprotein galactosyltransferase, CMP-sialic acid: glycoprotein sialyltransferase and UDP-galactose pyrophosphatase activities were measured in the endometrium of rat uteri during the oestrous cycle. The galactosyltransferase activity started to increase at dioestrus and reached a maximum on the afternoon of pro-estrus. The UDP-galactose pyrophosphatase activity changed in a direction opposite to that of galactosyltransferase. The sialyltransferase activity was low during metoestrus and dioestrus, but began to rise on the morning of pro-oestrus, reaching a peak on the morning of oestrus. Previously, we have shown that oestradiol administration stimulated galactosyl- and sialyltransferase and inhibited pyrophosphatase activities several-fold in the endometrium of ovariectomized rats. Progesterone prevented the oestradiol effect on the enzymes. The changes in glycosyltransferase and pyrophosphatase activities during the oestrous cycle possibly bear a direct relationship to the ovarian hormones in the rat during the normal oestrous cycle. This relationship will then be conducive to increased synthesis of glycopolymers during ovulation. Furthermore, the lag of 18 h for a maximal rise of sialyltransferase following that of galactosyltransferase is consistent with the normal sequence of glycosylation that occurs in glycoprotein secretion.
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PMID:Glycosyltransferase and UDP-galactose pyrophosphatase activities in the endometrium during oestrous cycle of the rat. 55 72

Liver microsomal fractions catalyse the transfer of sialic acid from CMP-N-acetyl-neuraminic acid to various exogenous acceptors such as desialylated fetuin, desialylated human Tamm-Horsfall glycoprotein and desialylated bovine submaxillary-gland mucin. An increase in the rate of incorporation of sialic acid into desialylated glycoproteins was found after a lag period (7h) in regenerating liver. The increase was maximum 24h after partial hepatectomy for all acceptors tested. At later times after operation the sialyltransferase activity remained high only for desialylated fetuin. No soluble factors from liver or serum of partially hepatectomized animals influenced the activity of the sialyltransferases bound to the microsomal fraction. The sensitivity of sialyltransferases to activation by Triton X-100, added to the incubation medium, was unchanged in the microsomal preparation from animals 24h after sham operation or partial hepatectomy. The full activity of sialyltransferases towards the various desialylated acceptors showed some differences. Human Tamm-Horsfall glycoprotein was a good acceptor of sialic acid only when desialylated by mild acid hydrolysis. After this treatment, but not after enzymic hydrolysis, a decrease in molecular weight of human Tamm-Horsfall glycoprotein was observed. Further, the sialyltransferase activity as a function of incubation temperature gave different curves according to the acceptor used. The relationship between the biosynthesis of glycoproteins by regenerating liver and the sialyltransferase activity of microsomal fraction after partial hepatectomy is discussed.
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PMID:Sialyltransferase activity in regenerating rat liver. 59 33

Some properties of sialyltransferase activity in plasma and lymphocytes from patients with chronic lymphocytic leukemia were compared. Three distinct enzyme fractions were identified in plasma: (1) cation independent, irreversibly bound to agarose; (2) cation dependent, weakly bound to agarose; (3) strongly bound to agarose, lost upon dialysis. Lowering of the peripheral lymphocyte count by leukapheresis markedly decreased the level of serum sialyltransferase, suggesting the circulating lymphocyte is a source of the serum enzyme. The enzyme solubilized by detergent from lymphocytes showed a substantially lower Km for CMP-sialic acid than did the serum enzyme, was less sensitive to several inhibitors, was not irreversible bound to Agarose, and had a substantial cation requirement. The enzyme solubilized from the lymphocyte therefore generally resembles fraction 2 of serum.
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PMID:Some properties of sialyltransferase in plasma and lymphocytes of patients with chronic lymphocytic leukemia. 62 86

The substrate specificity and kinetic properties of a pure sialyltransferase from bovine colostrum have been examined. The transferase appears to incorporate sialic acid into the sequence, NeuAcalpha2 leads to 6Galbeta1 leads to 4GlcNAc, which is commonly found in glycoproteins. It has a strict substrate specificity for CMP-NeuAc and forms only the alpha2 leads to 6 sialyl linkage with beta-D-galactosides. N-Acetyllactosamine (Galbeta1 leads to 4GlcNAc) and asialo-glycoproteins containing the N-acetyllactosaminyl linkage at the nonreducing ends of the oligosaccharides prosthetic groups are the best acceptor substrates. Isomers of N-acetyllactosamine with beta1 leads to 3 or beta1 leads to 6 glycosidic linkages are less than 1% as effective as acceptor substates as the beta1 leads to 4-linked isomer. Lactose (Galbeta1 leads to 4Glc) is also a poor acceptor, indicating the importance of the 2-acetamido group in the N-acetylglucosaminyl residues. The unnatural substrate beta-methyl-L-arabinopyrano-side, a five-carbon analog of beta-methyl-D-galactoside which contains no 6-hydroxyl, also acts as a poor acceptor of the transferase and the sialylated product has been partially characterized. Kinetic properties of the enzyme in the presence and absence of inhibitors suggest that the transferase has an equilibrium random order mechanism.
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PMID:Enzymatic properties of beta-D-galactoside alpha2 leads to 6 sialytransferase from bovine colostrum. 84 33

Levels of glycoprotein:sialyltransferase activity (EC 2.4.99.1; CMP-acetyl-neuraminate:D-galactosyl-glycoprotein N-acetylneuraminyl-transferase) were measured in plasma of patients with neoplastic disease, and were found elevated above normal control values in 85% of patients examined. There was a correlation between enzyme levels and course of disea-e in 46 of 57 patients studied serially during therapy. Plasma sialyltransferase may be a useful marker enzyme for monitoring effectiveness of therapeutic programs for disseminated neoplasms.
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PMID:Alterations in plasma sialyltransferase levels in patients with neoplastic disease. 91 50


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