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)

We have investigated the ganglioside levels, composition and metabolism in two lines of doxorubicin-resistant cells and in the corresponding wild strains, the C6 rat glioblastoma and the HTC rat hepatoma. The only ganglioside present was GM3, and its level was increased 2-fold in C6 resistant cells and decreased nearly 2-fold in HTC resistant cells. A decrease of cytidine 5'-monophospho-N-acetylneuraminic acid:galactosylglucosylceramide sialyltransferase activity was observed in both resistant lines as compared to sensitive ones, and could not, therefore, explain the increase in the GM3 level observed in the C6 resistant line. Alterations of acid neuraminidase activity were also observed; a 5-fold decrease was noticed in the C6 resistant line and could account for the increase in the GM3 level observed in these cells; in contrast, a 2-fold increase of acid neuraminidase activity was noticed in the HTC resistant cells: together, with reduced synthesis, it could explain the decrease in the GM3 level observed in these cells. No alterations of exogenous ganglioside transport was exhibited by the C6 resistant cells.
Biochim Biophys Acta 1988 Dec 16
PMID:Alteration of ganglioside composition and metabolism in doxorubicin-resistant rat tumoral cells. 319 50

Sialyltransferase activity was assayed in rat intestinal cells isolated as fractions reflecting the villus-crypt axis of differentiation. In 13-day-old rats both endo- and exogenous sialyltransferase activity reached their maximum in undifferentiated crypt cells and their peaks overlapped. In contrast, sialyltransferase of the adult intestine was 4-fold lower than that of sucklings in the crypts, with slight tendency to be transferred to the villus cells. Hydrocortisone applied to 10-day-old rats caused three days later a precocious drop of sialyltransferase activity in the crypt cells. Unlike in vivo, glucocorticoid responsiveness was accompanied by increased sialyltransferase activity in fetal small intestine cultivated for 17 days.
FEBS Lett 1988 Dec 19
PMID:Effect of hydrocortisone on sialyltransferase activity in the rat small intestine during maturation. Changes along the villus-crypt axis and in fetal organ culture. 320 43

We previously reported that the synthesis of NeuAc(alpha 2-3)Gal(beta 1-4)GlcCer (GM3) ganglioside was preferentially enhanced during the differentiation of HL-60 cells into a monocyte/macrophage lineage induced by 12-O-tetradecanoylphorbol-13-O-acetate (TPA). Since exogenously added GM3 ganglioside was shown to be able to induce the differentiation of HL-60 cells into the monocyte/macrophage lineage in a synthetic medium, the functional role of the GM3 ganglioside increase during the differentiation of HL-60 cells has become the subject of much interest. In the present study, we investigated the activity of CMP-NeuAc:lactosylceramide sialyltransferase, which catalyzes the synthesis of GM3 ganglioside from lactosylceramide, in cells undergoing differentiation induced by two different reagents, TPA and 1 alpha,25-dihydroxy-vitamin D3, which induce the differentiation of HL-60 cells into the monocyte/macrophage lineage through different modes of action. We showed that the activation of CMP-NeuAc:lactosylceramide sialyltransferase and the increase in GM3 ganglioside were not related to the differentiated lineage but to the specific action of TPA, i.e. activation of protein kinase C.
J Biol Chem 1986 Dec 05
PMID:Activation of CMP-N-acetylneuraminic acid:lactosylceramide sialyltransferase during the differentiation of HL-60 cells induced by 12-O-tetradecanoylphorbol-13-acetate. 346 24

Serum samples of 7 cows from -10 to +10 days following parturition and of 7 calves from 0 to 20 days following birth were tested for the ability to inhibit mitogen-stimulated proliferation of lymphocytes, for cortisol and progesterone concentrations, and for sialic acid and sialyltransferase activity. Calf serum inhibited phytohemagglutinin (PHA)-stimulated proliferation of lymphocytes, with maximal inhibition at 12-24 h following birth, whereas no consistent immunosuppressive activity was detected in the maternal serum. Sialic acid was greatly elevated in calf serum (4.8 +/- 0.2 mumol/ml) relative to adult control values (1.3 +/- 0.1) and decreased continuously from day 0 to day 20. Sialic acid of maternal serum was slightly elevated prior to parturition (1.7 +/- 0.1) and increased to peak at 2.5 +/- 0.1 on day 8 following parturition. Sialyltransferase of both maternal and calf serum increased dramatically following parturition to peak at day 2. For calf serum, a moderate correlation was observed between sialic acid and cortisol concentration (r = 0.71) and between sialic acid and suppression of PHA-stimulated proliferation (r = 0.60). The results demonstrate that serum of 12-24 h-old calves is immunosuppressive in vitro, and suggest that changes in sialic metabolism may accompany cortisol-related immunosuppression in these animals.
J Reprod Immunol 1986 Dec
PMID:Immunosuppression, sialic acid, and sialyltransferase of neonatal and maternal bovine serum. 382 Jan 92

Neonatal capsaicin treatment induces significant changes in rat brain glycoconjugate metabolism. All glycosyltransferase activity involved either in glycoprotein or glycolipid biosynthesis was strongly enhanced. Higher enzymatic activities were obtained when capsaicin-treated rats (T1) had received an additional capsaicin dose (T2). In this case, the fucosyl and galactosyltransferase activities were markedly increased. However, the enhancement of sialyltransferase activity only affects the biosynthesis of glycoproteins and is not correlated with a significant change in ganglioside content. The present results suggest that the modulation of the microsomal glycosyltransferase activity, after capsaicin treatment, could not be stated up through a direct lipid interaction or a change in membrane properties because the phospholipid brain content is not significantly modified.
Neurosci Lett 1985 Dec 04
PMID:Modifications involved in brain glycoconjugate metabolism induced by neonatal capsaicin treatment. 408 29

Membrane glycopeptides were examined in human colonic adenocarcinoma and normal colonic mucosa. The carbohydrates of membrane glycopeptides were found to be markedly reduced in tumor tissue and the relative proportions of the various sugars were altered. Although all of the sugars were lower in tumor tissue when compared to the adjacent normal mucosa, galactosamine, fucose, and sialic acid were more significantly reduced. Examination of the blood group activity and lectin-binding properties of membrane glycopeptides revealed that specific carbohydrate structures had changed in the tumor tissue. Most striking of these changes was the disappearance of glycoprotein-associated blood group A activity. Assay of the enzyme responsible for synthesis of the blood group A determinant showed that this glycosyltransferase activity was greatly diminished in tumor tissue. A galactosyltransferase and a fucosyltransferase were also significantly lower in the tumor tissue whereas the levels of another galactosyltransferase and a sialyltransferase were unaltered. Glycosidase activities in the normal and tumor tissues were similar. The results show that an alteration in glycoprotein biosynthesis occurred during tumorigenesis that resulted in a modified membrane glycoprotein composition and that these changes are probably a reflection of reduced levels of the enzymes responsible for glycoprotein synthesis.
Proc Natl Acad Sci U S A 1974 Dec
PMID:Alterations of membrane glycopeptides in human colonic adenocarcinoma. 414 May 12

The effects of the membrane perturbing reagents linoleic acid and benzyl alcohol on the activities of four rat liver Golgi membrane enzymes, N-acetylglucosaminyl-, N-acetylgalactosaminyl-, galactosyl-, and sialyltransferases and several soluble glycosyltransferases, bovine milk galactosyl- and N-acetylglucosaminyltransferases and porcine submaxillary N-acetylgalactosaminyltransferases have been studied. In rat liver Golgi membranes, linoleic acid inhibited the activities of N-acetylgalactosaminyl- and galactosyltransferases by 50% or greater, sialyltransferase by 10-15%, and N-acetylglucosaminyltransferase not at all. The isolated bovine milk N-acetylglucosaminyltransferase and porcine submaxillary N-acetylgalactosylaminyltransferase were not inhibited but bovine milk galactosyltransferase was inhibited by 95% or greater. The inhibition by linoleic acid on Golgi membrane galactosyltransferase appears to be a direct effect of the reagent on the enzyme. Incorporation of bovine milk galactosyltransferase into liposomes formed from saturated phospholipids, DMPC, DPPC, and DSPC (dimyristoyl-, dipalmitoyl-, and distearoylphosphatidylcholine) prevented inhibition of the enzyme activity suggesting that the lipid formed a barrier which did not allow linoleic acid access to the enzyme. The water soluble benzyl alcohol was more effective in inhibiting enzymes of the isolated rat liver Golgi complex. All four glycosyltransferases were inhibited, the N-acetylglucosaminyl- and N-acetylgalactosaminyltransferases by more than 95%. A higher concentration of benzyl alcohol was necessary to inhibit the galactosyltransferases than was required for the other Golgi enzymes. Benzyl alcohol also inhibited the isolated bovine milk N-acetylglucosaminyl- and galactosyltransferases 90% to 95%, respectively, but did not affect the isolated porcine submaxillary gland N-acetylgalactosaminyltransferase. Benzyl alcohol did not inhibit the milk galactosyltransferase incorporated into DMPC or DPPC liposomes but showed a complex effect on the activity of the enzyme incorporated into DSPC vesicles, a stimulation of activity at low concentrations followed by an inhibition. A lipid environment consisting of saturated lipids appears to present a barrier to inhibiting substances such as linoleic acid and benzyl alcohol, or lipid may stabilize the active conformation of the enzyme. The different effects of these reagents on four transferases of the Golgi complex suggest that the lipid environment around these enzymes may be different for each transferase.
Biochim Biophys Acta 1982 Dec 08
PMID:The effect of linoleic acid and benzyl alcohol on the activity of glycosyltransferases of rat liver Golgi membranes and some soluble glycosyltransferases. 621 37

The postnatal development of skeletal muscle is characterized by changes in membrane function associated with N-linked glycoproteins. In the present study, early reactions involved in the synthesis of the dolichol-linked core oligosaccharide were examined in neonatal and adult rabbit skeletal muscle sarcoplasmic reticulum membranes. The initial rate of N-acetylglucosamine incorporation in the presence of exogenous dolichol phosphate was similar between neonate and adult (3.5-4.1 pmol of GlcNAc/min/mg). The Km values for UDP-GlcNAc and exogenous dolichol phosphate were similar. Tunicamycin (0.04-0.08 micrograms/ml) inhibited N-acetylglucosamine incorporation by 50%. UDP-GlcNAc pyrophosphatase activity was greater in neonatal membranes than adult (840 versus 350 pmol of GlcNAc-1-P/min/mg), explaining, in part, the greater enhancement of neonatal GlcNAc incorporation by pyrophosphatase inhibitors. Nucleotide-sugar pyrophosphatase inhibitors (alpha, beta-methylene ATP and dimercaptopropanol) increased the capacity of neonatal activity 4-fold and adult enzyme 2-fold. Analysis of dolichol-linked products by mild acid hydrolysis however, revealed that neonate had higher capacity for N,N'-diacetylchitobiosyl(pyro)phosphoryldolichol synthesis than adult. Mannosyltransferase and glucosyltransferase were elevated 6- and 5-fold in neonate compared to adult membranes. Neonate exhibited 4-fold greater GDP-Man pyrophosphatase activity than adult (500 versus 125 pmol of Man-1-P/min/mg). The Km for GDP-Man increased in the presence of exogenous dolichol phosphate. Increasing concentrations of exogenous dolichol phosphate did not equalize neonate and adult mannosyltransferase activity, indicating that the decline in activity during development was not due to a decrease in a pool of dolichol phosphate accessible to mannosyltransferase. Glucosyltransferase for the synthesis of glucosylphosphoryldolichol was also elevated 5-fold in neonatal compared to adult sarcoplasmic reticulum (7 versus 1.4 pmol of Glc/min/mg). In a previous study, it was reported that glycoprotein sialyltransferase activity decreased by a factor of 6.5 during the postnatal maturation and that total membrane hexose content of sarcoplasmic reticulum decreased by a factor of 8. Together, these results suggest that the postnatal development of skeletal muscle is characterized by coordinated changes in the expression of enzymes involved in both the "early" and "late" reactions of N-linked oligosaccharide biosynthesis.
J Biol Chem 1983 Dec 10
PMID:Formation of dolichol-linked sugar intermediates during the postnatal development of skeletal muscle. 631 23

Retinoic acid inhibits the proliferation of the murine melanoma clone S91-C-2 cells, enhances the glycosylation of specific cell surface sialoglycoproteins, and stimulates sialytransferase activity. Mutant clones, selected from the S91-C-2 cells for resistance to the growth-inhibitory effect of retinoic acid, were used to explore whether cell surface modulation by retinoic acid is related to growth inhibition. Glycoprotein synthesis was assessed by analysis of [3H]glucosamine incorporation into glycoconjugates, and cell surface sialo- and galactoglycoproteins were analyzed after radiolabeling by the NaIO4:NaB3H4 and the neuraminidase plus galactose oxidase:NaB3H4 methods, respectively. The cells were solubilized and the labeled molecules were separated by polyacrylamide gel electrophoresis and identified by fluorography. Sialytransferase activity was measured in detergent-solubilized cells, using cytidine 5' -monophosphate-[14C]sialic acid as a sugar donor and asialofetuin as an exogenous acceptor. The results demonstrated that retinoic acid enhanced [3H]glucosamine incorporation into a Mr 160,000 glycoprotein in the S91-C-2 cells but not in any of the resistant mutant clones, while the pattern of [35S]methionine-labeled proteins was not modified in either the sensitive or the resistant clones. Radiolabeling of a Mr 160,000 sialoglycoprotein on the surface of S91-C-2 and of several retinoic acid-sensitive subclones of S91-C-2 was augmented by retinoic acid. A considerably smaller effect was observed on the labeling of Mr 160,000 sialoglycoprotein on one of the resistant clones, and no significant effect could be detected on the other resistant mutant clones. Sialytransferase activity was increased 2- to 3-fold by retinoic acid in the S91-C-2 cells and in several sensitive subclones, but not in any of the resistant mutant clones. Tetradecanoylphorbol acetate, which inhibits the proliferation of both retinoic acid-sensitive and retinoic acid-resistant cells, failed to increase either sialyltransferase activity or cell surface labeling of sialoglycoproteins. These findings suggest that the ability of retinoic acid to stimulate sialyltransferase activity and glycosylation of cell surface glycoproteins is related to the growth-inhibitory effect of this compound.
Cancer Res 1984 Dec
PMID:Correlation of retinoic acid-enhanced sialyltransferase activity and glycosylation of specific cell surface sialoglycoproteins with growth inhibition in a murine melanoma cell system. 649 40

Golgi vesicle membranes from the Lec2 CHO glycosylation mutant translocate CMP-sialic acid at only 2% the rate of vesicles from wild-type CHO cells. The deficiency is specific, because vesicles from Lec2 cells can translocate UDP-N-acetylglucosamine, adenosine 3'-phosphate 5'-phosphosulfate, and UDP-galactose at rates comparable to those of vesicles from wild-type cells. Complementation analyses show that Lec2 mutants belong to the same genetic complementation group as clone 1021, a CHO mutant of similar phenotype. Both mutants have previously been shown to have a 90% reduction in the sialylation of glycoproteins and gangliosides compared with wild-type cells. However, 1021 cells appear to have normal levels of CMP-sialic acid, sialyltransferase activity, and endogenous acceptors for sialylation. It seems likely that the primary defect in Lec2 and 1021 cells is their inability to translocate CMP-sialic acid across Golgi vesicle membranes.
Cell 1984 Dec
PMID:Translocation across Golgi vesicle membranes: a CHO glycosylation mutant deficient in CMP-sialic acid transport. 649 37


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