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

---

Query: EC:2.4.99.6 (sialyltransferase)
1,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The rainbow trout (Oncorhynchus mykiss) CMPNeuAc:lactosylceramide alpha 2----3sialytransferase enzyme from RTH-149 cells has been characterized. 2. Transfer of sialic acid to lactosylceramide was optimal at a pH of 5.9, temperature of 25 degrees C, and in the pressure of 0.3% CF-54, 10 mM Mn2+, 0.1 M sodium cacodylate, and 2 mM ATP. 3. Golgi-rich membrane fractions of RTH-149 cells were found to be enriched in sialidase activity and as such the addition of 40 microM 2,3-dehydro-2-deoxy-N-acetylneuraminic acid was necessary to assay alpha 2----3sialyltransferase activity optimally. 4. Apparent Km for donor (CMPNeuAc) and acceptor (lactosylceramide) were found to be 243 microM and 34 microM, respectively. 5. The alpha 2----3sialyltransferase characterized was found to be primarily specific for lactosylceramide though minor activity with other glycolipid acceptors was observed. 6. The presence of another sialyltransferase with differing substrate specificity was noted. 7. Properties of this enzyme, compared to analogous mammalian enzymes, are discussed.
...
PMID:Characterization of a CMPNeuAc: lactosylceramide alpha 2----3sialyltransferase from rainbow trout hepatoma (RTH-149) cells. 206 Feb 83

CMP-N-acetylneuraminic acid: glycoprotein sialyltransferase activities were assayed in microsomal fractions from chicken liver and hepatoma, induced by the leukosis virus strain Mc-29, using asialofetuin as the substrate acceptor of N-acetylneuraminic acid. The effect of some nucleotides and metal ions on the enzyme activity was investigated. Kinetic studies revealed that the Km values toward asialofetuin at a saturation concentrations of CMP-N-acetylneuraminic acid for both liver and hepatoma enzymes are very closed, while V value was lower for the tumor enzyme. The liver and hepatoma enzymes have no exogenous Mn cations requirement and are inhibited by CTP, CMP and ATP. CMP was shown to act as a competitive inhibitor with an apparent Ki of 0.24 mM for the liver and 0.16 mM for hepatoma enzyme, respectively.
...
PMID:Partial characterization of microsomal sialyltransferase from chicken liver and hepatoma Mc-29: I. Effect of nucleotides and metal ions. 208 38

The CMP-sialic acids, cytidine 5'-(5-acetamido-3,5-dideoxy-beta-D-glycero-D-galacto-2-nonulopyranosy lonic acid monophosphate) (1) and cytidine 5'-(5-acetamido-9-O-acetyl-3,5-dideoxy-beta-D-glycero-D-galacto-2- nonulopyranosylonic acid monophosphate) (2) were prepared from CMP, phosphoenolpyruvate, N-acetylneuraminic acid or its 9-acetate, and a catalytic amount of ATP in the presence of immobilised pyruvate kinase, nucleoside monophosphate kinase, inorganic pyrophosphatase, and CMP-sialic acid synthetase. CMP-NeuAc (1) was used as a donor of N-acetylneuraminic acid in the reaction catalysed by immobilised porcine liver beta-D-Galp-(1----4)-alpha-D-GlcpNAc-(2----6)-sialyltransferase, alpha-D-Neup5Ac-(2----6)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1--- -2)-alpha-D- Man-OMe (5) was obtained on a 0.1-mmol scale by enzymic sialylation of beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----2)-alpha-D-Man-OMe (4), prepared by enzymic galactosylation of beta-D-GlcpNAc-(1----2)-alpha-D-Man-OMe (3). Likewise, using 2, alpha-D-Neup-5,9Ac2-(2----6)-beta-D-Galp-(1----4)-D-GlcpNAc (7) was obtained from N-acetyl-lactosamine (6).
...
PMID:The use of immobilised glycosyltransferases in the synthesis of sialyloligosaccharides. 237 8

Some properties of the sialyltransferase activity of homogenates prepared from normal human platelets were investigated using asialo-fetuin as substrate. The enzyme activity was optimal at pH 6.5 and was stimulated by divalent cations in the order Mg2+ greater than Mn2+ greater than Ca2+. Buffers of high ionic strength strongly reduced the activity. ATP and ADP were not inhibitors at 0.1 mM concentration, but AMP, CTP and CMP reduced the activity by 15-30%. A native endogenous acceptor for the enzyme activity was located in the platelet homogenates. The range of fetuin-sialyltransferase activity found in platelets isolated from 6 normal donors was 79 +/- 39 pmol/h/mg protein (mean +/- SD). The platelets of patients with Glanzmann's thrombasthenia and the Bernard-Soulier syndrome, which are characterized by different membrane glycoprotein deficiencies, were shown to have fetuin-sialyltransferase activities within the normal range indicating that the membrane glycoprotein defects in the platelets of these patients are not associated with the absence of sialyltransferase activity.
...
PMID:Glycoprotein-sialyltransferase activity of normal human, thrombasthenic and Bernard-Soulier platelets. 616 43

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

The composition of tissue gangliosides is thought to result mainly from the active regulation and selective expression of specific enzymes responsible for their metabolism. In the last few years, we have purified several rat brain sialyltransferases to homogeneity; the availability of these highly purified enzymes enabled us to investigate their regulation and expression at the molecular level. Thus, we studied the regulation of sialyltransferase activities, in particular, CMP-NeuAc:GM1 and CMP-NeuAc:LacCer sialyltransferases by a phosphorylation/dephosphorylation mechanism. Protein kinase C was added to a standard enzyme assay mixture containing [gamma-32P]ATP, and the activity of the enzyme was measured after various incubation times. We found that treatment of several sialyltransferases by protein kinase C decreased their activities in a time-dependent manner. Analyses of 32P-labeled amino acids revealed that the major phosphorylation site of CMP-NeuAc:GM1 alpha 2-->3 sialyltransferase (ST-IV) was serine and that for CMP-NeuAc:LacCer alpha 2-->3 sialyltransferase (ST-I) was primarily threonine. Partial recovery of the enzyme activity could be achieved by treatment of the phosphorylated sialyltransferases with rat brain protein phosphatase. We conclude that the activities of sialyltransferases can be modulated by protein kinase C and protein phosphatase and this may represent a potential regulatory mechanism for ganglioside biosynthesis.
...
PMID:Regulation of sialyltransferase activities by phosphorylation and dephosphorylation. 772 15

We have developed a system that recreates in vitro the generation of post-Golgi vesicles from an isolated Golgi fraction prepared from vesicular stomatitis virus- or influenza virus-infected Madin-Darby canine kidney or HepG2 cells. In this system, vesicle generation is temperature- and ATP-dependent and requires a supply of cytosolic proteins, including an N-ethylmaleimide-sensitive factor distinct from NSF. Cytosolic proteins obtained from yeast were as effective as mammalian cytosolic proteins in supporting vesicle formation and had the same requirements. The vesicles produced (50-80 nm in diameter) are depleted of the trans Golgi marker sialyltransferase, contain the viral glycoprotein molecules with their cytoplasmic tails exposed, and do not show an easily recognizable protein coat. Vesicle generation was inhibited by brefeldin A, which indicates that it requires the activation of an Arf-like GTP-binding protein that promotes assembly of a vesicle coat. Vesicles formed in the presence of the nonhydrolyzable GTP analogue guanosine 5'-3-O-(thio)triphosphate retained a nonclathrin protein coat resembling that of COP-coated vesicles, and sedimented more rapidly in a sucrose gradient than the uncoated ones generated in its absence. This indicates that GTP hydrolysis is not required for vesicle generation but that it is for vesicle uncoating. The activity of a Golgi-associated protein kinase C (PKC) was found to be necessary for the release of post-Golgi vesicles, as indicated by the capacity of a variety of inhibitors and antibodies to PKC to suppress it, as well as by the stimulatory effect of the PKC activator 12-O-tetradecanoylphorbol-13-acetate.
...
PMID:The in vitro generation of post-Golgi vesicles carrying viral envelope glycoproteins requires an ARF-like GTP-binding protein and a protein kinase C associated with the Golgi apparatus. 866 71

Large-scale enzymatic synthesis of oligosaccharides, which contain terminal N-acetyl-neuraminic acid residues requires large amounts of the sialyltransferase and the corresponding sugar-nucleotide synthetase, which is required for the synthesis of the sugar-nucleotide donor, CMP-Neu5Ac. Using genes cloned from Neisseria meningitidis, we constructed a fusion protein that has both CMP-Neu5Ac synthetase and alpha-2,3-sialyltransferase activities. The fusion protein was produced in high yields (over 1200 U/L, measured using an alpha-2,3-sialyltransferase assay) in Escherichia coli and functionally pure enzyme could be obtained using a simple protocol. In small-scale enzymatic syntheses, the fusion protein could sialylate various oligosaccharide acceptors (branched and linear) with N-acetyl-neuraminic acid as well as N-glycolyl- and N-propionyl-neuraminic acid in high conversion yield. The fusion protein was also used to produce alpha-2,3-sialyllactose at the 100 g scale using a sugar nucleotide cycle reaction, starting from lactose, sialic acid, phosphoenolpyruvate, and catalytic amounts of ATP and CMP.
...
PMID:The synthesis of sialylated oligosaccharides using a CMP-Neu5Ac synthetase/sialyltransferase fusion. 970 65

Neisseria gonorrhoeae strain JB1 was previously shown to be defective in the sialylation of lipoologosaccharide (LOS) by exogenous CMP-NANA. The LOS components synthesized by the mutant now have been shown by mass spectrometry to be similar to those in the parental strain, F62, and to include the 4.5 kDa widely conserved lacto-N-neotetraose component that can be sialylated. The same two LOS components could be sialylated on the surface of the mutant and parental strains. One major component was sialylatable after chemical extraction of the LOS from either strain. These data confirm that the mutant, JB1, retains the ability to synthesize the LOS target required for the conversion by sialylation of serum-sensitive gonococci to serum resistance. A single base frame-shift mutation was found in the lst gene from the mutant, resulting in the replacement of the final 61 amino acids at the C-terminus of the sialyltransferase by four residues. Seventeen independent clones of the lst gene were isolated from the parental strain, but none of them complemented the sialyltransferase defect of the mutant and no sialyltransferase activity expressed from the clones could be detected in Escherichia coli. Although the data suggest that the mutant might be defective in genes at more than one chromosomal locus and that multiple loci are essential for sialyltransferase synthesis and activity, the alternative possibility, that DNA adjacent to the lst gene encodes a product which is toxic to E. coli, cannot be excluded. The site of insertion of the transposon Tn1545-Delta3 in strain JB1 was cloned and sequenced. The transposon is located in an intergenic region adjacent to genes for a putative ATP-dependent transport protein, but encoding no recognizable function relevant to LOS sialylation. Evidence that transposon Tn1545-Delta3 is unstable in gonococci is presented.
...
PMID:Characterization of a sialyltransferase-deficient mutant of Neisseria gonorrhoeae strain F62: instability of transposon Tn1545 delta3 in gonococci and evidence that multiple genetic loci are essential for lipooligosaccharide sialylation. 987 53

An Escherichia coli strain expressing three recombinant enzymes, i.e., cytidine 5'-monophosphate (CMP) kinase, sialic acid aldolase and cytidine 5'-monophosphate N-acetylneuraminic acid (CMP-NeuAc) synthetase, was utilized as a biocatalyst for the production of CMP-NeuAc. Both recombinant E. coli extract and whole cells catalyzed the production of CMP-NeuAc from CMP (20 mM), N-acetylmannosamine (40 mM), pyruvate (60 mM), ATP (1 mM), and acetylphosphate (60 mM), resulting in 90% conversion yield based on initial CMP concentration used. It was confirmed that endogenous acetate kinase can catalyze not only the ATP regeneration in the conversion of CMP to CDP but also the conversion of CDP to CTP. On the other hand, endogenous pyruvate kinase and polyphosphate kinase could not regenerate ATP efficiently. The addition of exogenous acetate kinase to the reaction mixture containing the cell extract increased the conversion rate of CMP to CMP-NeuAc by about 1.5-fold, but the addition of exogenous inorganic pyrophosphatase had no influence on the reaction. This E. coli strain could also be employed as an enzyme source for in situ regeneration of CMP-NeuAc in a sialyltransferase catalyzed reaction. About 90% conversion yield of alpha2,3-sialyl-N-acetyllactosamine was obtained from N-acetyllactosamine (20 mM), CMP (2 mM), N-acetylmannosamine (40 mM), pyruvate (60 mM), ATP (1 mM), and acetyl phosphate (80 mM) using the recombinant E. coli extract and alpha2,3-sialyltransferase.
...
PMID:Production of cytidine 5'-monophosphate N-acetylneuraminic acid using recombinant Escherichia coli as a biocatalyst. 1235 62


1 2 Next >>

---