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)

Lines of KB cells resistant to Sendai virus-induced cytolysis have been isolated and characterized (Toyama, S., Toyama, Su., and Uetake, H. (1977) Virology 76, 503-515). This study is concerned with the nature of this mutation. Plasma membrane fractions from Sil cells were found to have decreased amount of sialic acid and the same amount of galactose as compared to the membranes from parental KB cells. Sil cells exhibited an increase in sensitivity to toxic effects of ricin and a decrease in sensitivity to wheat germ agglutinin. Binding of wheat germ agglutinin to Sil cells was markedly decreased. Several membrane glycoproteins of Sil cells migrated slightly faster than the corresponding bands of wild type membrane when examined by gel electrophoresis in sodium dodecyl sulfate. Sil cells had decreased sialyltransferase activity that catalyzed the transfer of sialic acid residues from CMP-N-acetylneuraminic acid to glycoprotein acceptors containing Gal beta 1 leads to 3GalNAc alpha 1 leads to O-Ser(Thr) chain. The decreased enzyme activity could not be accounted for by the presence of inhibitors, altered pH optimum, or increased sialidase or CMP-sialic acid hydrolase activities. These results indicate that a molecular basis for the Sil cell phenotype might be the deficiency of sialyltransferase.
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PMID:Deficient cytidine monophospho-N-acetylneuraminic acid: glycoprotein sialyltransferase activity in a clone of KB cells with altered cell fusion ability. 640 1

Turpentine induced inflammation has been shown to elevate liver sialyl- and galactosyltransferase activities (Turchen, B., Jamieson, J.C., Huebner, E., and van Caeseele, L. (1977) Can. J. Zool. 55, 1567-1571; Lombart, C., Sturgess, J., and Schachter, H. (1980) Biochem. Biophys. Acta 629, 1-12). We now report that serum sialyl-, but not galactosyltransferase activities are significantly elevated in turpentine inflammation. A liver slice system is used to demonstrate that liver releases large amounts of sialyltransferase activity into medium after inflammation, whereas only a low level of galactosyltransferase activity is released. Studies with rat and human asialo-alpha 1-acid glycoprotein as acceptors, coupled with the use of lactose to confirm the nature of the linkages formed, showed that Gal beta 1 leads to 4GlcNAc alpha 2 leads to 6 sialyltransferase is released from liver in turpentine inflammation and is mainly responsible for the elevated sialyltransferase activity found in serum. The alpha 2 leads to 6 sialyltransferase is exhibiting the properties of a typical acute phase reactant.
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PMID:Studies on the effect of inflammation on rat liver and serum sialyltransferase. Evidence that inflammation causes release of Gal beta 1 leads to 4GlcNAc alpha 2 leads to 6 sialyltransferase from liver. 641 2

In order to study structure-function relationships of lysosomal enzymes, human liver beta-N-acetylhexosaminidase (2-acetamido-2-deoxy-beta-D-hexoside acetamidodeoxyhexohydrolase, EC 3.2.1.52) has been purified by an extraction/affinity chromatography/ion-exchange procedure. The isoenzymes A and B, native as well as neuraminidase-treated, were incubated with a partially purified preparation of bovine colostrum sialyltransferase (CMP-N-acetylneuraminate: D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1). Native beta-N-acetylhexosaminidases were found to be poor acceptors for the sialyltransferase used. However, incorporation of sialic acid into neuraminidase-treated beta-N-acetylhexosaminidase A and B amounted to a 58 to 72% saturation of the theoretical acceptor sites, respectively. The acceptor specificity of the sialyltransferase suggests that Gal beta(1 leads to 4)-GlcNAc units may be present on at least part of the beta-N-acetylhexosaminidase A and B molecules. However, oligomannosidic-type chains may also occur on the lysosomal enzyme, as shown by sugar composition of the enzyme. The presence and/or amount of sialic acid residues does not appear to affect the kinetic properties of beta-N-acetylhexosaminidase A and B towards 4-methylumbelliferyl glycoside substrate.
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PMID:Sialylation in vitro of purified human liver beta-D-N-acetylhexosaminidase. 645 69

Rat liver Golgi apparatus are shown to have a CMP-N-acetylneuraminate: N-acetylglucosaminide (alpha 2----6)-sialyltransferase which catalyzes the conversion of the human milk oligosaccharide LS-tetrasaccharide-a (NeuAc alpha 2----3Gal beta 1---- 3GlcNAc beta 1----3Gal beta 1----4Glc) to disialyllacto -N- tetraose containing the terminal sequence: (formula: see text) found in N-linked oligosaccharides of glycoproteins. The N-acetylglucosaminide (alpha 2----6)-sialyltransferase has a marked preference for the sequence NeuAc alpha 2----3-Gal beta 1---- 3GlcNAc as an acceptor substrate. Thus, the order of addition of the two sialic acids in the disialylated structure shown above is proposed to be first the terminal sialic acid in the NeuAc alpha 2----3Gal linkage followed by the internal sialic acid in the NeuAc alpha 2---- 6GlcNAc linkage. Sialylation in vitro of the type 1 branches (Gal beta 1---- 3GlcNAc -) of the N-linked oligosaccharides of asialo prothrombin to produce the same disialylated sequence is also demonstrated.
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PMID:Biosynthesis of a disialylated sequence in N-linked oligosaccharides: identification of an N-acetylglucosaminide (alpha 2----6)-sialyltransferase in Golgi apparatus from rat liver. 654 92

Using a number of branched and unbranched oligosaccharides, glycoproteins and artificial glycoproteins bearing Gal(beta 1-4)GlcNAc-R termini as acceptors (where R represents H, oligosaccharide, oligosaccharide-protein or fatty acid-protein), the comparative rates of transfer of NeuAc by the Gal(beta 1-4)GlcNAc(NeuAc-Gal) (alpha 2-6)-sialyltransferase of embryonic chicken liver were determined. Acceptor substrates were utilized at levels approximating physiological, near the Km value of the best acceptor, desialylated alpha 1 acid glycoprotein. The sialyltransferase has a marked preference for multi-branched acceptors. From the specificity data, it is concluded that the enzyme binds at least two Gal(beta 1-4)GlcNAc termini of an acceptor molecule, and that the relative orientation of the branches is an important factor determining the rate of catalysis by the enzyme. The use of oligosaccharides as acceptors to study sialyltransferase catalyses is emphasized. Results are discussed in the context of the mode of assembly of sialoside termini of known glycoprotein structures in vivo.
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PMID:Comparative rates of transfer of N-acetylneuraminic acid to acceptors bearing one or more Gal(beta 1-4)GlcNAc terminus by the Gal(beta 1-4)GlcNAc(NeuAc-Gal) (alpha 2-6)-sialyltransferase from embryonic chicken liver. Utilization of oligosaccharides as acceptors in sialyltransferase assays. 661 29

The specificity of fetal calf liver and ovine and porcine submaxillary gland N-acetylgalactosaminide alpha 2 leads to 6 sialyltransferase was investigated with acceptors of low and high molecular weight containing O-glycosidically linked carbohydrate chains. It appeared that fetal calf liver microsomes were able to transfer sialic acid to C-6 of GalNAc in NeuAc(alpha 2 leads to 3)Gal(beta 1 leads to 3)GalNAc-R, in which the aglycon could be protein as well as p-nitrophenol (Nph). The substrates Gal(beta 1 leads to 3)GalNAc-R and GalNAc-R were inactive as acceptor with this enzyme source. Ovine and porcine submaxillary gland microsomes were both active with GalNAc-protein, Gal(beta 1 leads to 3)GalNAc-protein, NeuAc[alpha 2 leads to 3)Gal(beta 1 leads to 3)GalNAc-protein and NeuAc(alpha 2 leads to 3)Gal(beta 1 leads to 3)GalNAc alpha-Nph, but not with GalNAc alpha-Nph and Gal(beta 1 leads to 3)GalNAc alpha-Nph. The N-acetylgalactosaminide alpha 2 leads to 6 sialyltransferase which had been purified to homogeneity from porcine submaxillary gland [Sadler, J. E., Rearick, J. I. and Hill, R. L. (1979) J. Biol. Chem. 254, 5934-5941], was able to sialylate all three protein acceptors, but was virtually inactive with each of the three p-nitrophenyl glycosides. Our studies indicate that two N-acetylgalactosaminide alpha 2 leads to 6 sialtransferases exist acting on O-glycosidically linked carbohydrate chains. The first enzyme, present in fetal calf liver, has a narrow specificity with regard to the oligosaccharide structure, but shows no specificity for the aglycon. Based on its specificity this enzyme can be designated as an [alpha-N-acetylneuraminosyl 2 leads to 3-beta-galactosyl 1 leads to 3]-alpha-N-acetylgalactosaminide alpha 2 leads to 6 sialyltransferase. The second enzyme, present in porcine submaxillary gland, has an absolute requirement for protein as the aglycon. Once this condition is fulfilled, the enzyme is able to transfer sialic acid to each of the three oligosaccharide chains and thus the enzyme is an alpha-N-acetylgalactosaminylprotein alpha 2 leads to 6 sialyltransferase. The data also seem to suggest that ovine and porcine submaxillary gland microsomes contain, in addition to the latter enzyme activity, the alpha 2 leads to 6 sialyltransferase with the strict oligosaccharide specificity.
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PMID:Aglycon specificity of fetal calf liver and ovine and porcine submaxillary gland alpha-N-acetylgalactosaminide alpha 2 leads to 6 sialyltransferase. 661 53

A method has been developed to determine the activities of specific sialyltransferases by analysis of the products of the reaction. This method, which utilizes high performance liquid chromatography, distinguishes addition of sialic acid to the N-acetylgalactosamine vs. galactose residues of the mucin disaccharide Gal beta(1 leads to 3)GalNac, and can be used to distinguish formation of the 3'- and 6'-isomers of sialyllactose. For the bovine, ovine, and porcine submaxillary extracts, more than 95% of the activity with asialo ovine submaxillary mucin is due to formation of NeuAc alpha(2 leads to 6)GalNAc. With lactose as the acceptor, more than 95% of the alpha(2 leads to 3) isomer is produced. Activity with asialofetuin is due solely to the O-linked chain, with relative activity toward the galactose vs. GalNAc residues of 0.32, 1.5, and 0.10 for bovine, ovine, and porcine, respectively. The rat submaxillary gland extract showed equal formation of 3'- and 6'-sialyllactose, and very low activity with asialo ovine submaxillary mucin. However, at least 40% of the activity toward the Gal beta(1 leads to 3)GalNAc disaccharide of asialofetuin was directed toward the GalNAc residue. The relative preference of the N-acetylgalactosaminide alpha(2 leads to 6) sialyltransferase for a monosaccharide vs. a substituted GalNAc may play a role in regulation of chain length during mucin synthesis.
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PMID:Specificity of submaxillary gland sialyltransferases. 663 63

Golgi vesicles were isolated and purified from rat liver, in which the specific activities of glycosyltransferases (e.g. GM3: CMP-NeuAc sialyltransferase, GD3-synthase; GM3: UDP-GalNAc galactosaminyltransferase, GM2-synthase) were 50-60 times enriched relative to microsomes or total homogenate. Synthesis of gangliosides GM2 and GM1 in such Golgi vesicles is, in the absence of any detergents, stimulated 6- and 20-fold, respectively, by phosphatidylglycerol. Other phospholipids like dolichyl phosphate, phosphatidylethanolamine and phosphatidylserine are also significantly stimulatory. Tunicamycin inhibits the synthesis of gangliosides GM2 and GM1 in isolated Golgi vesicles, but only in the absence of detergents. The dependence on phosphatidylglycerol and the degree of inhibition by tunicamycin of the synthetic activities are strictly dependent on the intactness of the Golgi vesicles: both phenomena become increasingly less evident when the vesicles are pelleted, and frozen and thawed several times, and completely disappear when the vesicles are solubilized by the detergents or disrupted by ultrasonication. Furthermore, tunicamycin inhibition is reversible by increased concentration of phosphatidylglycerol. In pronase-treated Golgi vesicles, which retain full enzyme activity, both phospholipid-dependence and tunicamycin inhibition of the synthetic activity disappear completely. When freshly prepared Golgi vesicles are incubated with 125 microM UDP [3H]Gal for 10 min at 30 degrees C, the nucleotide sugar is found to be transported into the vesicles at the rate of about 85 pmoles/mg protein/min, 92% of radiolabel remaining firmly bound with membrane. Tunicamycin inhibits this transport in a concentration-dependent manner. The results show that, while the mechanism of phosphatidylglycerol induced stimulation of the synthetic activity remains unclear, tunicamycin inhibits ganglioside biosynthesis by blocking the transport of the nucleotide sugar across Golgi vesicles and not inhibiting the transferase enzyme directly.
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PMID:Ganglioside biosynthesis in rat liver golgi apparatus: stimulation by phosphatidylglycerol and inhibition by tunicamycin. 674 31

A beta-D-galactoside alpha 2 leads to 6 sialyltransferase was purified 500-fold in 14% yield from 14-day embryonic chicken liver. Characterization of the product of the sialyltransferase catalysis was accomplished by separation and permethylation of double-labelled ([14C]NeuAc, [3H]Gal) oligosaccharides following their release from the glycoprotein fetuin by hydrazinolysis. The enzyme transfers NeuAc to Gal(beta 1 leads to 4)GlcNAc(beta 1 leads to)R-terminated oligosaccharides; no activity was found towards Gal(beta 1 leads to 3)GalNAc(alpha 1 leads to)R structures. The trisaccharide. NeuAc(alpha 2 leads to 6)Gal(beta 1 leads to 4)Glc, was shown to be a good inhibitor of the sialyltransferase. Kinetic investigations of the enzyme indicate it to have a sequential, random bi-bi mechanism.
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PMID:Kinetic parameters of a beta-D-galactoside alpha 2 leads to 6 sialyltransferase from embryonic chicken liver. 675 14

Rat liver Golgi was found to contain a sialyltransferase activity which would convert lacto-N-tetraose (Gal beta 1 goes to 3GlcNAc beta 1 goes to 3Gal beta 1 goes to 4Glc) to LS-tetrasaccharide a (NeuAc alpha 2 goes to 3Gal beta 1 goes to 3GlcNAc beta 1 goes to 3Gal beta 1 goes to 4Glc). The enzyme has been partially purified by affinity chromatography on CDP-hexanolamine agarose. Of the glycoprotein substrates examined, it utilizes the Gal beta 1 goes to 3GlcNAc sequence found on the asparagine-linked oligosaccharides of prothrombin as its preferred acceptor substrate, and thus has been tentatively designated a Gal beta 1 goes to 3GlcNAc alpha 2 goes to 3 sialyltransferase. The partially purified enzyme has an acceptor specificity distinct from other purified mammalian sialyltransferases which synthesize the NeuAc alpha 2 goes to 3Gal beta 1 goes to 3 GalNAc and NeuAc alpha 2 goes to 6 GalNAc sequences common to oligosaccharides O-linked to threonine or serine and the NeuAc alpha 2 goes to 6Gal beta 1 goes to 4GlcNAc sequence found on oligosaccharides N-linked to asparagine.
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PMID:Identification of a Gal beta 1 goes to 3GlcNAc alpha 2 goes to 3 sialyltransferase in rat liver. 706 22


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