Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.99.10 (sialyltransferase)
 1,547 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Triton X-100 is increasingly effective in solubilizing human liver glycoprotein (asialofetuin) sialytransferase (CMP-N-acetylneuraminate:D-galactosyl-glycoprotien N-acetylneuraminyltransferase, EC 2.4.99.1) activity as its concentration is increased in the homogenizing buffer. At the optimal concentration of 1.5% (v/v), essentially all of the homogenate sialyltransferase activity was solubilized into the supernatant fluid. Higher concentrations of Triton X-100 inhibited sialyltransferase activity. Several kinetic properties of the solubilized asialofetuin-sialyltransferase activity were compared to those of the membrane-bound enzyme(s) (in homogenates made without Triton X-100 or in resuspended pellets). No major difference was apparent, suggesting that solubilization has not significantly altered the properties of sialyltransferase. The solubilized sialyltransferase activity is quite unstable, losing approximately 50% of its activity after one week of storage at 4 degrees C. Various detergents (Zwittergent, sodium taurocholate and sodium deoxycholate) are differentially effective in stabilizing the solubilized activity. Sodium taurocholate (1.5%, w/v) was most effective with no loss in activity after 40 days and minimal loss (14%) after 60 days storage at 4 degrees C. The solubilized sialyltransferase preparation retains full activity after storage in the frozen state (-20 degrees C) for at least 159 days.
Biochim Biophys Acta 1979 Sep 12
PMID:Solubilization and stabilization of human liver glycoprotein sialyltransferase. 3 14

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.
Proc Natl Acad Sci U S A 1979 Sep
PMID:Differential activities of glycolipid glycosyltransferases in Tay-Sachs disease: studies in cultured cells from cerebrum. 29 63

It was demonstrated that microsomal membranes from frog liver contain at least two different sialyltransferases involved in the synthesis of alpha 2 leads to 3 and alpha 2 leads to 6 oligosaccharide isomers. Studies on acceptor specificity of the sialyltransferase system with respect to low molecular acceptors revealed its similarity to the mammalian sialyltransferase system. However, sharp distinctions were observed in sialylation of mammalian glycoproteins. It was assumed that that the disaccharide unit of the acceptor oligosaccharide chain is a structural element, which in necessary but not sufficient for glycoprotein recognition by sialyltransferases.
Biokhimiia 1979 Sep
PMID:[Properties of membrane-bound sialyltransferase from rana temporaria liver]. 31 99

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.
Biochem J 1977 Sep 15
PMID:Sialyltransferase activity in regenerating rat liver. 59 33

Some patients with thyrotropin (TSH)-producing pituitary tumors are more hyperthyroid than others despite similar TSH levels in serum, suggesting that qualitatively different TSH molecules with differing bioactivities may be secreted by different tumors. We used ricin and lentil lectin-affinity chromatography to test whether the TSH oligosaccharides varied among 12 patients with TSH-producing tumors. We found that each tumor secreted heterogeneous isoforms of TSH that differed in their extents of exposed galactose (Gal) residues, and their degrees of sialylation and core fucosylation. These biochemical parameters also varied markedly for TSH secreted by different tumors. Isoforms appeared to reflect poor sialyltransferase activity in two tumors and efficient sialyltransferase in the remainder. TSH secreted by tumors was more fucosylated than TSH secreted by control euthyroid persons. There was an inverse relationship between the sialylation and fucosylation of tumor TSH. No simple relationship between TSH oligosaccharide structures and bioactivity was evident, although mixtures of isoforms having the least and most sialylated TSH seemed to be the most bioactive clinically. In three patients from whom serum and medium TSH were both available, TSH in serum was more sialylated than TSH secreted by the tumor in vitro, perhaps reflecting slow clearance of sialylated isoforms from the circulation. Core fucosylation of serum TSH was less than that of medium TSH. These data prove that human tumors secrete TSH with heterogeneous oligosaccharide structures.
Metabolism 1992 Sep
PMID:Ricin and lentil lectin-affinity chromatography reveals oligosaccharide heterogeneity of thyrotropin secreted by 12 human pituitary tumors. 151 16

We investigated biosynthesis, intracellular transport and release of beta-galactoside alpha-2,6-sialyltransferase in a dexamethasone-inducible rat hepatoma cell line. Confluent cells were induced by 10 microM dexamethasone for 24 h, and metabolically labelled with [35S]methionine/cysteine, followed by immunoprecipitation of sialyltransferase and electrophoretic/fluorographic analysis. The 35S-labelled enzyme was synthesized as a 46-kDa precursor, converted to an intermediate 47-kDa form after 1 h, and gradually to a mature form of 48 kDa within the following 3 h. By means of either tunicamycin inhibition of N-glycosylation or cleavage of N-glycans from isolated sialyltransferase using N-glycosidase F, the sizes of the precursor and the mature form were reduced to 41 kDa and 43 kDa, respectively. After a 4-h chase, treatment with endoglycosidase H revealed two distinct molecular forms of sialyltransferase, bearing either two N-acetyllactosamine-type or one oligomannose-type and one N-acetyllactosamine-type N-linked sugar chain. In addition, sialyltransferase became sensitive to neuraminidase digestion after a 4-h chase. The half-life of intracellular [35S]sialyltransferase was estimated at 3 h. A soluble form was detectable in the supernatant, 2 h after the pulse. Only 12% of the initially labelled sialyltransferase was found in the medium after 12 h, while 73% of the enzyme was degraded intracellularly. To characterize a possible intracellular degradation site, we studied intracellular transport in the presence of either secretion-blocking or acidotropic agents or protease inhibitors. Degradation was significantly delayed by all treatments. Our results show that sialyltransferase follows the secretory pathway as a membrane protein and is retained at a late Golgi stage. We suggest that the bulk of sialyltransferase in rat hepatoma cells is diverted to a post-Golgi degradation pathway. This route contrasts with the post-Golgi trafficking of beta-1,4-galactosyltransferase in HeLa cells, which is constitutively secreted [Strous, G. J. A. M. & Berger, E. G. (1982) J. Biol. Chem. 257, 7623-7628].
Eur J Biochem 1992 Sep 01
PMID:Biosynthesis and intracellular transport of alpha-2,6-sialyltransferase in rat hepatoma cells. 152 30

The subcellular distribution of polyisoprenyl pyrophosphate phosphatase activity has been examined in rat brain by assaying the release of 32Pi from [beta-32P]dolichyl pyrophosphate (Dol-P-P) as described previously (Scher,M.G. and Waechter, C.J. (1984) J. Biol. Chem., 259, 14580-14585). The highest specific activities of Dol-P-P phosphatase in rat brain were found in the Golgi-enriched light microsomal, synaptic plasma membrane and heavy microsomal fractions. A comparative analysis of the distribution of galactosyltransferase and dolichol kinase reveals that Dol-P-P phosphatase activity co-fractionates with galactosyltransferase activity, and that the high level found in the Golgi-enriched fraction is not due to cross-contamination with heavy microsomes. When beta-labelled C95 Dol-P-P and the C95 allylic polyisoprenyl pyrophosphate (Poly-P-P) were compared as substrates for the Golgi-enriched light microsomal and heavy microsomal fractions, similar Km values were calculated for the two pyrophosphorylated substrates for each membrane fraction. Based on these kinetic analyses, the enzyme(s) catalysing this reaction do not distinguish between substrates containing saturated or allylic alpha-isoprene units. When Dol-P-P phosphatase activity was assessed in submicrosomal fractions obtained from rat liver by two separate procedures, the highest specific activity was also detected in the Golgi-enriched fraction. While the specific activities for Dol-P-P phosphatase and sialyltransferase were in the relative order of Golgi greater than smooth endoplasmic reticulum (ER) greater than rough ER, the relative order of dolichol kinase was rough ER greater than smooth ER greater than Golgi.(ABSTRACT TRUNCATED AT 250 WORDS)
Glycobiology 1991 Sep
PMID:Golgi-enriched membrane fractions from rat brain and liver contain long-chain polyisoprenyl pyrophosphate phosphatase activity. 166 43

To establish the basis for the reduced expression of the X determinant on leukemic blasts and the changes in antigenic expression that occur during myeloid maturation, the presence on myeloid cells of X and related structures was examined in conjunction with studies on the activities of the glycosyltransferases involved in their biosynthesis. Expression of X and sialyl-X was weak on blasts in comparison with neutrophils despite the presence of the requisite precursor structures. Much higher levels of 3-fucosyltransferase activity were found in blasts than in neutrophils when nonsialylated substrates were used, but, whereas the enzyme in neutrophils reacted equally well with 3'-sialylated and nonsialylated acceptors, the enzyme in blasts showed a marked preference for nonsialylated substrates. 6'-Sialyltransferase activity was strong in blasts but was not detectable in neutrophils, whereas a much lower level of 3'-sialyltransferase activity was present in both blasts and neutrophils. Dimethyl sulfoxide-induced maturation of HL60 cells was associated with (1) a decrease in both 6'-sialyltransferase and 3-fucosyltransferase activities, (2) a change in the substrate specificity of 3-fucosyltransferase towards that found in mature cells, and (3) increased cell surface expression of sialyl-X. These results suggest that the reduced expression of X in myeloblasts is related to the presence of the strong 6'-sialyltransferase, which uses the precursor substrate at the expense of the 3-fucosyltransferase and prevents the synthesis of X and sialyl-X. The developmental regulation of the levels of 3'- and 6'-sialyltransferases, and the level and specificity of the 3-fucosyltransferases, therefore controls the expression of X and its degree of sialylation.
Blood 1991 Sep 15
PMID:Enzymic control of the expression of the X determinant (CD15) in human myeloid cells during maturation: the regulatory role of 6-sialytransferase. 167 56

Functional maturation of B lymphocytes correlates with expression of the B lineage-specific cell surface glycoprotein CD22. Two CD22 polypeptides have been characterized and suggested to play a role in B cell-B cell interaction as well as in B cell adhesion to monocytes. In this work we provide evidence that CD22 is directly involved in the cognate interaction between B and T cells. One of the two CD22 polypeptides, CD22 beta, interacts with a specific ligand on a subpopulation of CD4+ T cells. Our results suggest that the T cell ligand of CD22 is CD45RO, an isoform of the leukocyte common antigen class of phosphotyrosine phosphatases associated with the helper T cell phenotype. We further demonstrate that CD22 recognizes a second ligand, CD75, expressed predominantly on activated B cells and shown to be a cell surface alpha 2-6 sialyltransferase.
Cell 1991 Sep 20
PMID:The B lymphocyte adhesion molecule CD22 interacts with leukocyte common antigen CD45RO on T cells and alpha 2-6 sialyltransferase, CD75, on B cells. 154 99

Neuraminidase substrates suitable for analysis of linkage specificity were enzymically synthesized in good yield by linking N-acetylneuraminic acid (Neup5Ac) to O-6 and O-3 of 4-nitrophenyl beta-D-galactopyranoside with beta-D-galactoside-alpha-(2----6)-sialyltransferase and beta-D-galactoside-alpha-(2----3)-sialyltransferase, respectively. By use of these substrates, a convenient colorimetric assay method was developed for the determination of linkage specificity of bacterial and viral neuraminidases. The substrates are incubated with viral or bacterial neuraminidase and subsequently treated with beta-D-galactosidase to convert the liberated 4-nitrophenyl beta-D-galactopyranoside to 4-nitrophenol. The amount of liberated 4-nitrophenol is equivalent to the amount of Neup5Ac released from the substrate, thus allowing measurement of neuraminidase activity. The results showed that bacterial and viral neuraminidases can discriminate between these two compounds, making them useful substrates for the rapid determination of neuraminidase linkage specificity.
Carbohydr Res 1991 Sep 30
PMID:Synthesis of linkage-specific sialoside substrates for colorimetric assay of neuraminidases. 180 82


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