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)

Synthetic sialic acid analogues varying in the substitutents at position C-9 were analyzed for their ability to replace the natural receptor determinant for influenza C virus, N-acetyl-9-O-acetylneuraminic acid (Neu5,9Ac2). By incubation of erythrocytes with sialyltransferase and the CMP-activated analogues, the cell surface was modified to contain sialic acid with one of the following C-9 substituents: an azido, an amino, an acetamido, or a hexanoylamido group. Among these, only 9-acetamido-N-acetylneuraminic acid (9-acetamido-Neu5Ac) was able to function as a receptor determinant for influenza C virus as indicated by the ability of the virus to agglutinate the modified red blood cells. In contrast to the natural receptors, 9-acetamido-Neu5Ac-containing receptors were found to be resistant against the action of sialate 9-O-acetylesterase, the viral receptor-destroying enzyme. No difference in the hemolytic activity of influenza C virus was detected when analyzed with erythrocytes containing either Neu5,9Ac2 or 9-acetamido-Neu5Ac on their surface. This finding indicates that cleavage of the receptor is not required for the viral fusion activity. The sialic acid analogues should be useful for analyzing not only the importance of the receptor-destroying enzyme of influenza C virus, but also other biological processes involving sialic acid.
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PMID:A synthetic sialic acid analogue is recognized by influenza C virus as a receptor determinant but is resistant to the receptor-destroying enzyme. 161 56

After growth of gonococci in the presence of cytidine monophospho-N-acetyl-neuraminic acid (CMP-NANA), their 4.5-kD lipooligosaccharide (LOS) component was increased by approximately 400 daltons, whereas the LOS of strains lacking the 4.5-kD component were unaffected. Expression of mAb-defined epitopes on the 4.5-kD component was decreased on LOS of strains grown in CMP-NANA, and treatment of the LOS with neuraminidase reversed this affect. Gonococci incubated with human PMNs also had decreased expression of the 4.5-kD+ epitopes. A detergent extract of gonococci incorporated radiolabeled NANA in the LOS, suggesting the presence of a sialyltransferase in gonococci. Exogenous sialyltransferases also could use LOS as an acceptor.
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PMID:In vitro and in vivo modification of Neisseria gonorrhoeae lipooligosaccharide epitope structure by sialylation. 169 81

The gangliosides of human hepatoma biopsies, human hepatoma cell lines, and diethylnitrosamine-induced rat hepatomas were examined. These malignant tissues all expressed increased content of disialolactosylceramide (GD3) with respect to their normal counterparts. During the induction of rat hepatoma by diethylnitrosamine, an increase in GD3 levels appeared as early as 12 wk after initiation of diethylnitrosamine, concurrent with the appearance of precancerous hepatocytes. GD3 levels gradually increased to a peak of 4 times that of normal rat liver at 20 wk. CMP-NeuAc:GM3 sialyltransferase, the enzyme that synthesizes GD3 by transfer of sialic acid to GM3, also had tumor-associated elevation during the course of diethylnitrosamine-induction of rat hepatomas. To investigate the relationship of oncogene transformation and changes in ganglioside biosynthesis, NIH 3T3 cells transfected DNAs from human hepatoma or nasopharyngeal carcinoma were studied. The transfectants each expressed the same ganglioside composition, including a detectable level of GD3, as well as enhanced activity of CMP-NeuAc:GM3 sialyltransferase. A correlation between the tumor DNA transfection and the augmentation of GD3 in malignant cells is discussed. Because of the early appearance of GD3 in hepatoma and its possible relationship to oncogene activation, GD3 may be a potentially useful early tumor marker.
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PMID:Enhanced expression of ganglioside GD3 in human and rat hepatocellular carcinoma cells and NIH 3T3 cells transfected with human tumor DNAs. 170 52

Previous studies have shown that purified mitochondrial outer membrane is able to catalyze the transfer of sialic acid from CMP-Neu5Ac to an exogenous asialoglycoprotein acceptor, asialofetuin. Considering the heterogeneity of the glycan chains borne by this glycoprotein, an investigation of mitochondrial sialyltransferase activities was undertaken. Our data provide evidence for the existence of two distinct sialyltransferases in purified mitochondrial outer membranes. The use of different acceptor substrates, the temperature dependence of these enzymes, and their different sensitivity towards a sulfhydryl reagent, p-CMB, allowed us to discriminate between a galactoside alpha(2-3) sialyltransferase and a galactoside alpha(2-6) sialyltransferase presumably involved in the sialylation of O- and N-glycan chains of glycoprotein, respectively. These results are discussed in terms of mitochondrial autonomy for post-translational events.
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PMID:Sialylation processes in mitochondria: evidence for two distinct sialyltransferases located in the outer membrane. 172 30

The activity of four different sialyltransferases acting on N- or O-linked chains of glycoproteins was studied in brains of 19 days-old embryos, 1-day-old newborns and adult rats. By using asialofetuin, fetuin and N-acetyllactosamine as acceptors, it has been possible to measure independently the following enzyme activities: CMP-NeuAc:Gal beta 1-3GalNAc alpha(2-3)-sialyltransferase (EC 2.4.99.4), CMP-NeuAc:Gal beta 1-4GlcNAc alpha(2-3)-sialyltransferase (EC 2.4.99.6), CMP-NeuAc:Gal beta 1-4GlcNAc alpha(2-6)-sialyltransferase (EC 2.4.99.1) and CMP-NeuAc:NeuAc alpha 2-3Gal beta 1-3GalNAc alpha(2-6)-sialyltransferase (EC 2.4.99.7). The specific activity of the first three enzymes which act on asialylated acceptors showed a 2.6-fold decrease in a parallel manner after ontogenic development, while the activity of NeuAc alpha 2-3Gal beta 1-3GalNAc alpha(2-6)-sialyltransferase was four times lower in adult than in embryonic brain, showing a stronger dependence on ontogenic development. Despite the higher level of sialyltransferases able to act on glycoproteins, in fetal brain these glycoproteins do not contain a higher amount of sialic acid.
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PMID:Sialyltransferases of developing rat brain. 172 33

Glycoproteins containing N-linked oligosaccharides were prepared from plasma and liver microsomes of rats aged 0-5 weeks, and galactose and sialic acid content were determined. The sialic acid/galactose ratios in plasma membrane N-glycans remained at about 1 throughout the postnatal period, suggesting that most of the galactose residues are sialylated. In the same way, it was suggested that most of the galactose residues of microsomal N-glycans were sialylated at 0, 4 and 5 weeks of age, but that the degree of sialylation was lower at the other ages, with a minimum at 2 weeks. When the activities of sialyltransferase and galactosyltransferase in liver Golgi membranes were determined, age-dependent changes were found, not only in the specific activities of the enzymes, but also in the Golgi membrane content per g of liver. The activity of galactosyltransferase per g of liver increased immediately after birth, whereas that of sialyltransferase remained at a low level for 2 weeks and then increased to a constant level at 4 weeks. It is probable that this delayed increase in the activity of sialyltransferase results in the decreased sialylation of microsomal N-glycans at 1, 2 and 3 weeks. Sialyltransferase was solubilized from the liver microsomes of rats aged 2, 3 and 4 weeks and characterized. Phosphocellulose column chromatography separated the activity into two subfractions, designated transferase I and transferase II in the order of elution. The increase in total sialyltransferase activity during this period was caused mainly by an increase in transferase I. Rechromatography of each transferase from 3-week-old rats after neuraminidase treatment showed that transferase I but not transferase II contained sialic acid residue(s) and that desialylated transferase I was eluted in a similar way as transferase II. Although the apparent Km value for CMP-N-acetylneuraminic acid and the heat stability of transferase I were different from those of transferase II, the difference was abolished by treating transferase I with neuraminidase, suggesting that transferase II may be a desialylated form of transferase I. These changes in the sialylation of membrane glycoproteins, including sialyltransferase, may be related to the control of liver growth during postnatal development.
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PMID:Postnatal changes in sialylation of glycoproteins in rat liver. 174 45

Sialyltransferase activity was determined on normospermic men sperm cells (greater than 80 x 10(6) sperm/ml and 75% motility) and oligospermic infertile sperm cells (less than 20 x 10(6) sperm/ml and less than 20% motility) and asthenospermic (greater than 40 x 10(6) sperm/ml and less than 10% motility). Sialytransferase activity is quantified by means of the transference of radioactivity of CMP-3H-sialic acid toward the exogenous acceptor (asialofetuin). The enzyme substrate complexes formed in presence of phosphotungstic acid result precipitated insoluble, which was retained on glass fiber filter. The sialyltransferase activity decrease in oligospermic sperm cells 62 +/- 3% and in the asthenospermic decreased 57 +/- 4% with respect normospermic sperm cells. The decrement on sialyltransferase activity in the infertile sperm, permits to assume that this enzyme probably participates as a direct cause of its pathology with detrimental structural and functional integrity of the plasma membrane.
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PMID:[Sialyltransferase activity in the spermatic membrane and its relation to human fertility and sterility]. 179 18

CMP-sialic acid:GM3 sialyltransferase (GD3 synthase; EC 2.4.99.8) was characterized in a membrane-enriched preparation (P2 pellet) from mouse embryos at embryonic day 12 (E-12). Gangliosides GD3 and GM3 were the major radiolabeled products of the reaction. Optimum GD3 synthase activity was obtained at pH 6.0 using 0.1% detergent Triton CF-54. The Km values for GM3 and CMP-sialic acid were 55 and 80 microM, respectively. The Vmax value was calculated as 622 pmol/mg protein/hr. Ganglioside GD3, as end product, induced a two-step reduction of enzyme activity in the range of concentrations from 0 to 34 microM (40%) and from 150 to 300 microM (65%). The rate of GD3 formation was similar in whole embryos and in embryo head and body regions. GD3 synthase activity in tw1/tw1 mutant mouse embryos, which express defects in neuronal differentiation, was only 40% of that in normal wild-type (+/+) embryos. Enzyme activity in heterozygous (+/twl) embryos was similar to that in +/+ embryos. These findings suggest that the reduced GD3 synthase activity in the mutants might arise as a consequence of failed nervous system development and might reflect a secondary rather than a primary effect of the mutation.
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PMID:Ganglioside GD3 biosynthesis in normal and mutant mouse embryos. 182 26

Poly-alpha-2,8 N-acetylneuraminic acid (polySia) is an important virulence factor in infections caused by Escherichia coli K1 and Neisseria meningitidis B. In E. coli K1 a membranous CMP-NeuAc: poly-alpha-2,8 sialosyl sialyltransferase (polysialyltransferase) complex catalyses the synthesis of linear polySia chains. The complex also elongates sialyl oligomers that serve as exogenous acceptors. The gene encoding a polysialyltransferase of E. coli has been identified by subcloning and DNA sequence analysis. The subcloned DNA fragment codes for a polypeptide with a molecular mass of 47 kDa catalysing the in vitro synthesis of polySia by elongation of exogenous acceptors.
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PMID:Complete nucleotide and deduced protein sequence of CMP-NeuAc: poly-alpha-2,8 sialosyl sialyltransferase of Escherichia coli K1. 182 Jan 97

A Gal beta 1-4GlcNAc alpha (2-6)-sialyltransferase from human liver was purified 34,340-fold with 18% yield by dye chromatography on Cibacron Blue F3GA and cation exchange FPLC. The enzyme preparation was free of other sialyltransferases. It did not contain CMP-NeuAc hydrolase, protease, or sialidase activity, and was stable at -20 degrees C for at least eight months. The donor substrate specificity was examined with CMP-NeuAc analogues modified at C-5 or C-9 of the N-acetylneuraminic acid moiety. Affinity of the human enzyme for parent CMP-NeuAc and each CMP-NeuAc analogue was substantially higher than the corresponding Gal beta 1-4GlcNAc alpha (2-6)-sialyltransferase from rat liver.
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PMID:Purification and characterization of alpha (2-6)-sialyltransferase from human liver. 182 12


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