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)

GMP-N-Acetylneuraminate: galactosyl-glycoprotein sialytransferase (CMP-N-acetylneuraminate: D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) activity was identified in the human cervical epithelium. The enzyme has a pH optimum of 6.0, a temperature optimum of 28 degrees C, and demonstrates a partial requirement for Triton X-100. Michaelis constants for asialofetuin and CMP-N-acetyl[14C]neuraminic acid are 0.64 . 10(-5) M (expressed as the concentration of terminal galactose residues) and 2.05 . 10(-5) M, respectively. Sialytransferase demonstrated minimal affinity for the low molecular weight acceptors tested, and may have a requirement for a glycoprotein acceptor having a terminal N-acetyllactosamine (Gal beta (1 leads to 4)GlcNAc) type structure. Cytidine nucleotides are potent inhibitors of the sialyltransferase reaction; CMP acts as a competitive inhibitor.
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PMID:Glycosyltransferases of the human cervical epithelium. II. Characterization of a CMP-N-acetylneuraminate: galactosyl-glycoprotein sialyltransferase. 616 92

Fetal calf liver microsomes were found to be capable of sialylating 14C-galactosylated ovine submaxillary asialomucin. The main oligosaccharide product chain could be obtained by beta-elimination under reductive conditions and was identified as NeuAc alpha 2 leads to 3Gal beta 1 leads to 3GalNAcol (where GalNAcol represents N-acetylgalactosaminitol) by means of high performance liquid chromatography (HPLC) analysis and methylation. The branched trisaccharide Gal beta 1 leads to 3(NeuAc alpha 2 leads to 6)-GalNAcol and the disaccharide NeuAc alpha 2 leads to 6GalNAcol were not formed. Very similar results were obtained when asialofetuin and antifreeze glycoprotein were used as an acceptor. When 3H-sialylated antifreeze glycoprotein ([3H]NeuAc alpha 2 leads to 3Gal beta 1 leads to 3GalNAc-protein) was incubated with fetal calf liver microsomes and CMP-[14C]NeuAc, a reduced tetrasaccharide could be isolated. The structure of this product chain appeared to be [3H]NeuAc alpha 2 leads to 3Gal beta 1 leads to 3([14C]NeuAc alpha 2 leads to 6)GalNAcol, as established by means of HPLC analysis, specific enzymatic degradation with Newcastle disease virus neuraminidase, and periodate oxidation. These data indicate that fetal calf liver contains two sialyltransferases involved in the biosynthesis of the O-linked bisialotetrasaccharide chain. The first enzyme is a beta-galactoside alpha 2 leads to 3 sialyltransferase which converts Gal beta 1 leads to 3 GalNAc chains to the substrate for the second enzyme, a (NeuAc alpha 2 leads to 3Gal beta 1 leads to 3)GalNAc-protein alpha 2 leads to 6 sialyltransferase. The latter enzyme does not sialylate GalNAc or Gal beta 1 leads to 3GalNAc units but is capable of transferring sialic acid to C-6 of GalNAc in NeuAc alpha 2 leads to 3Gal beta 1 leads to 3GalNAc trisaccharide side chains, thereby dictating a strictly ordered sequence of sialylation of the Gal beta 1 leads to 3 GalNAc units in fetal calf liver.
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PMID:Biosynthesis of the O-glycosidically linked oligosaccharide chains of fetuin. Indications for an alpha-N-acetylgalactosaminide alpha 2 leads to 6 sialyltransferase with a narrow acceptor specificity in fetal calf liver. 619 Aug 2

Neuraminidase activity of Rous sarcoma virus transformed chick embryo fibroblasts (RSV-CEF) was assayed using an exogenous substrate, neuraminlactitol-[3H], and endogenous, cell surface [14C]-N]-acetyl-neuraminic acid. RSV-CEF had higher neuraminidase activity toward both substrates than did chick embryo fibroblasts (CEF) or nontransformed, Rous associated virus infected CEF (RAV-CEF). The total sialic acid content of RSV-CEF was lower than CEF or RAV-CEF, and more of the total sialic acid was accessible to extracellular Clostridium perfringens neuraminidase. Activity of the enzymes synthesizing and degrading the substrate for sialyltransferase, cytidine-5'-monophosphate-N-acetyl-neuraminic acid (CMP-AcNeu) was measured in order to determine whether control of substrate levels for sialyltransferase might contribute to the decreased levels of glycoprotein bound sialic acid. No change in activity of these enzymes was found in RSV-CEF as compared to CEF or RAV-CEF.
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PMID:Neuraminidase activity and cell surface sialic acid turnover in Rous sarcoma virus transformed chick embryo fibroblasts. 626 45

The zona pellucida receptor for spermatozoa has not been identified and the mechanism by which spermatozoa traverse the zona pellucida has not been elucidated. It is proposed that the zona pellucida receptor is a glycoprotein and the receptor per se is galactosamine or N-acetyl galactosamine. The mechanism by which spermatozoa transverse the zona pellucida may be by its structural modification, by the transfer of spermatozoal sialic acid. In addition, male infertility resulting from oligozoospermia or polyzoospermia, may be due to lack of spermatozoal bound sialyltransferase. A total of 43 semen samples were examined for cytidine monophosphate-sialic acid synthetase and sialyltransferase activities. It was found that both these enzymes are present in seminal plasma and bound to the spermatozoa. The spermatozoal bound enzymes may be derived from the seminal plasma which may be a limiting factor in terms of infertility.
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PMID:Seminal plasma biochemistry II: seminal plasma and spermatozoal cytidine monophosphate-sialic acid synthetase and sialyltransferase activities. 626 56

In regenerating rat liver the activities of CMP-N-acetylneuraminate hydrolase and UDP-galactose pyrophosphatase were decreased to 40-50% of control values within 35 h after partial hepatectomy. In the same time period the activities of sialyltransferase and galactosyltransferase were increased, and the initial sharp decrease in the carbohydrate content of liver and serum glycoproteins was largely restored. The antiparallel nature of these events is suggestive of an involvement of nucleotide-sugar-hydrolysis enzymes in rat liver glycoprotein biosynthesis.
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PMID:Increased glycosylation capacity in regenerating rat liver is paralleled by decreased activities of CMP-N-acetylneuraminate hydrolase and UDP-galactose pyrophosphatase. 631 60

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.
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PMID:Formation of dolichol-linked sugar intermediates during the postnatal development of skeletal muscle. 631 23

A cytokine preparation from rat peritoneal exudate cells was studied. The preparation was pronase sensitive and heat labile, but was insensitive to trypsin treatment. Administration to rats resulted in elevated serum levels of alpha 1-acid glycoprotein, sialyltransferase activities and cortisol, but depressed serum albumin levels; in addition, hepatic sialyltransferase activities were increased and hepatic beta-galactosidase and beta-N-acetylhexosaminidase activities were depressed.
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PMID:Studies on rat cytokines as mediators of the acute phase response. 634 Jun 81

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


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