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)

Optimal assay conditions were determined for four glycosyltransferases in rat small intestinal mucosal homogenates and the regional distribution and cellular localization of these enzymes was studied. For each glycosyltransferase, similar levels of activity were found in duodenal, proximal jejunal and distal ileal segments; activities of the galactosyltransferases were lower in the distal jejunal-proximal ileal segment. Planar section studies indicated that the undifferentiated crypt cells had significantly higher levels of sialyltransferase activities in the jejunum and ileum than the mature villus cells. A similar crypt to villus gradient was found for a galactosyltransferase in the ileum. These data suggest that glycoprotein synthesis may be active in the undifferentiated crypt cells and that certain glycosyltransferases may serve as marker enzymes for cellular differentiation in the intestine.
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PMID:Regional and cellular localization of glycosyltransferases in rat small intestine. Changes in enzymes with differentiation of intestinal epithelial cells. 4 96

As the initial step toward the cytochemical localization of glycosyl-transferases in situ, biochemical determinations of these enzyme activities from onion root tips and L1210 cells were performed before and after fixation as well as in the presence of lead ions. Glycosyltransferase activity from roots fixed in buffered formaldehyde or glutaraldehyde before homogenization decreased as the concentration of the fixative or fixation time was increased. Formaldehyde fixation was less inhibitory than glutaraldehyde; 35% of the glycosyltransferase activity was retained after 30 min fixation in 2% formaldehyde while 25% of the enzyme activity remained after a similar fixation in glutaraldehyde. Substantially higher levels of L1210 cell glycosyltransferase activity were retained after a 30 min 2% formaldehyde fixation (60% sialyltransferase; 82% galactosyltransferase), but inhibition by glutaraldehyde was similar to that observed for onion root galactosyltransferase. Glycosyltransferase from formaldehyde-fixed roots was inhbited 35% by lead nitrate, but sialytransferase from formaldehyde-fixed L1210 cells was unaffected by lead ions. These findings are encouraging for further studies aimed at the development of cytochemical technique to localize glycosyltransferase in plant and animal tissues.
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PMID:Glycosyltransferases in plant and animal tissues effects of fixation and lead on enzyme activity. 10 86

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 sialyltransferase and galactosyltransferase activities of the Golgi-rich fraction from rat liver were enhanced by the binding of wheat germ agglutinin (WGA). The sialytransferase was more sensitive than the galactosyltransferase to the WGA. Maximal stimulation of the galactosyltransferase activity resulted from the binding of 60--80 micrograms WGA to the Golgi membrane, while only 40 micrograms of WGA produced a maximal enhancement in the sialyltransferase activity. Within 5 min of WGA binding, the Golgi sialytransferase activity was doubled. After the initial binding of WGA to the Golgi fraction, the galactosyltransferase activity was decreased by 30%. However, in 15 min the activity was doubled by the binding of WGA. The activities of both enzymes were further enhanced by incubation for up to 90 min. The stimulation of both sialyltransferase and galactosyltransferase activities by WGA was reversed by N-acetyl-D-glucosamine (GlcNAc), the specific inhibitor of agglutination by WGA. Complete reversal of the enhanced activity was observed after 20--30 min in the presence of 1 micromol GlcNAc. The association constant for the binding of WGA to the Golgi membranes was calculated to be 4.16 X 10(-6) M from a Steck-Wallach plot. The 'n' value or mean binding sites was calculated as 5.26 X 10(-5) M/mg of Golgi membrane protein.
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PMID:The effect of wheat germ agglutinin on sialyl and galactosyltransferases of rat liver Golgi membranes. 48 41

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

We have measured sialyltransferase, galactosyltransferase, and fucosyltransferase as sell as 5'-nucleotidase in the serum of breast cancer patients. Serum sialyltransferase values in 65 normal healthy females ranged from 2.6 to 8.5 units, with a mean of 5.4. In 25 women with operable primary breast cancer, serum sialyltransferase levels were found to be between 6.2 and 15.4 units. Marked elevation of this enzyme level (range, 8.8 to 36 units) was observed in 48 patients with metastatic breast cancer. Galactosyltransferase and fucosyltransferase measurements, however, showed considerable overlap between the controls and the cancer patients. On the other hand serum 5'-nucleotidase and sialyltransferase in breast cancer patients showed very similar patterns. Thus, serum 5'-nucleotidase values in 44 normal females ranged from 11.4 to 23.2 units, whereas the levels found in 30 patients with metastasis were between 25 and 71.8 units. The tissue origin of abnormal levels of serum glycosyltransferases and 5'-nucleotidase was discussed in relation to their physiological significance as well as their role as markers for diagnosing early malignant breast neoplasm and for monitoring the extent of metastasis.
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PMID:Alterations in serum glycosyltransferases and 5'-nucleotidase in breast cancer patients. 62 76

Elevated levels of three plasma glycosyltransferases were associated with neoplasia in cancer patients, notably those with tumor metastatic to liver. We examined levels of sialyltransferase, galactosyltransferase, and fucosyltransferase in metastatic tumor and apparently uninvolved host liver tissue in attempts to delineate possible sources of elevated plasma enzyme levels. Highest levels of fucosyltransferase activity were found associated with tumor tissue; in contrast, sialyltransferase and galactosyltransferase activity was often highest at the tumor-liver interface.
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PMID:Glycosyltransferase levels in tumors metastatic to liver and in uninvolved liver tissue. 87 59

The effect of temperature on the activity of galactosyl- and sialyltransferases of rat liver Golgi membranes and the galactosyltransferase of serum has been studied. Arrhenius plots for three enzymes were different. Sharp breaks in the curves, indicative of phase transitions were observed for sialyltransferase (28 degree C) of Golgi and galactosyltransferase (34 degree C) of serum but not for galactosyltransferase of Golgi. The activation energy was greater above the break (above 28 degree C) than below for sialyltransferase of Golgi; The activation energy was lower (above 34 degree C) for galactosyltransferase of serum than below. Electron microscopic freeze replicas showed a patchy distribution of particles which increased as the temperature was raised accompanied by smooth areas. This was interpreted as representing lateral phase separation of the membrane components.
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PMID:The effect of temperature on the galactosyl- and sialyltransferases and on the ultrastructure of Golgi membranes. 95 16

Two variant mouse L cell lines (termed CL 3 and CL 6) have been selected for resistant to ricin, a galactose-binding lectin with potent cytotoxic activity. The resistant lines exhibit a 50 to 70% decrease in ricin binding and a 300- to 500-fold increase in resistance to the toxic effects of ricin. Crude membrane preparations of CL 3 cells have increased sialic acid content (200% of control), while the galactose, mannose, and hexosamine content is within normal limits. Both the glycoproteins and glycolipids of CL 3 cells have increased sialic acid, with the GM3:lactosylceramide ratios for parent L and CL 3 cells being 0.29 and 1.5, respectively. In contrast, the membranes of CL 6 cells have a decrease in sialic acid, galactose, and hexosamine content with mannose being normal. Both cell lines have specific alterations in glycosyltransferase activities which can account for the observed membrane sugar changes. CL 3 cells have increased CMP-sialic acid:glycoprotein sialyltransferase and GM3 synthetase activities, while CL 6 cells have decrease UDP-GlcNAc:glycoproteinN-acetylglucosaminyltransferase and DPU-galactose:glycoprotein galactosyltransferase activities. The increased sialic acid content of CL 3 cells serves to mask ricin binding sites, since neuraminidase treatment of this cell line restores ricin binding to essentially normal levels. However, the fact that neuraminidase-treated CL 3 cells are still 45-fold resistant to ricin indicates that either a special class of productive ricin binding sites is not being exposed or that the cell line has a second mechanism for ricin resistance.
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PMID:Isolation and characterization of two mouse L cell lines resistant to the toxic lectin ricin. 100 11


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