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)

The postnatal developmental profiles of the protein-bound sialic acid content and the activities of CMP-N-acetylneuraminic acid (CMP-AcNeu) synthetase (EC 2.7.7.43) and glycoprotein sialyltransferase, enzymes involved in sialoglycoprotein biosynthesis, were estimated in the rat brain. The sialoglycoprotein level appeared to increase 2-fold from birth to about 20 days of age, which correlates with the outgrowth of the cell processes in this period. In contrast, the activities per g wet tissue of the enzymes were highest at birth and showed decreasing tendencies during maturation. This revealed that, at least at a certain stage during development, the sialyltransferase is present in structures other than synaptic membranes, since the new-born rat brain is devoid of these membranes. The developmental profile of the endogenous, sialic acid accepting molecules was very similar to that of the sialoglycoproteins. It was concluded that cerebral sialoglycoprotein biosynthesis during postnatal development is not limited by the activities of the synthetase and the transferase, but may largely depend on the production of the endogenous acceptors, which are presumed to be the natural precursors for the sialoglycoproteins.
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PMID:Sialoglycoprotein synthesis in developing rat brain. 117 8

The pathway for biosynthesis of sialic acid capsular polysaccharide was examined in Neisseria meningitidis serogroup B strain M986 and in strain PRM102, an isogenic mutant defective in polysaccharide production. Strain PRM102 was found to possess only 25% of the level of sialyltransferase activity that was found in strain M986, but it had wild-type levels of both the N-acetylneuraminic acid (NANA) condensing enzyme and the CMP-NANA synthetase. A new meningococcal enzyme, a CMP-NANA hydrolase, was found in both meningococcal strains. This enzyme generated CMP and NANA from CMP-NANA, had a Km of 0.88 microM, had a Vmax of 10.75 nmol of NANA produced per h per mg of protein, and was completely inhibited by 45.3 microM CMP. The sialyltransferase, which also had CMP-NANA as substrate, was insensitive to CMP addition. Subcellular fractionation and purification of cytoplasmic and outer membranes on sucrose density gradients revealed that both the sialyltransferase and the CMP-NANA hydrolase were cytoplasmic membrane associated. The NANA condensing enzyme and the CMP-NANA synthetase were found to be cytosolic. A working hypothesis for the regulation of sialic acid polysaccharide synthesis was developed. The CMP-NANA hydrolase with its high affinity for CMP-NANA regulates polysaccharide formation by the sialyltransferase, whereas CMP, a product of both the sialyltransferase and the CMP-NANA hydrolase, modulates the activity of the hydrolase on the cytoplasmic membrane.
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PMID:Physiology of sialic acid capsular polysaccharide synthesis in serogroup B Neisseria meningitidis. 630 82

N-Glycolylglucosamine 8 was synthesized in 4 steps from anisal glucosamine, via the new crystalline monochloracetyl derivatives 3, 4 and 7. N-Glycolylneuraminic acid 10 was prepared in 59% yield starting from pyruvate and a mixture of 8 and its manno epimer 9 in a 2:3 ratio, with immobilized sialic acid aldolase. Neu5Gc 10 was converted into CMP-NeuGc 11 in the presence of immobilized calf brain CMP-sialate synthetase. Finally 11 was used as a donor in the transfer to the acceptor beta-D-Gal-(1-3)-beta-D-GalNAc-OBn 12 catalyzed by a preparation of porcine liver (2-3)-alpha-sialyltransferase, roughly purified by a chromatography on Cibacron Blue-agarose. alpha-Neu5Gc-(2-3)-beta-D-Gal-(1-3)-beta-D-GalNac-OBn 13 isolated in 56% yield was deprotected to give the non-reducing terminal sequence of GM1b glycolylated ganglioside, which might be expressed in human tumors.
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PMID:Combined chemical and enzymatic synthesis of the sialylated non reducing terminal sequence of GM1b glycolylated ganglioside, a potential human tumor marker. 785 74

Linear and branched glycopeptides containing multiple sialyl-N-acetyllactosamine side chains have been synthesized using a combined chemical and enzymatic approach. Peptide backbones in which beta-GlcNAc-Asn residues were incorporated were obtained in good yields by optimized solid-phase synthesis following the Boc strategy. The resulting multivalent glycopeptides were galactosylated in near-quantitative yields using bovine galactosyltransferase, UDP-galactose, and calf alkaline phosphatase that destroys the inhibiting side product UDP. Subsequent enzymatic sialylation yielded the desired glycopeptides containing asparagine-linked sialyl-N-acetyllactosamine side chains. The compounds were characterized by 1H NMR and FABMS. Recombinant sialyltransferase and CMP-sialate synthetase were used for the enzymatic synthesis of sialosides on a preparative scale. The synthetic glycopeptides were tested as inhibitors of influenza virus to cells, revealing that most of the multivalent sialoglycopeptides exhibit increased binding that depends on the spacing when compared to monovalent compounds. A possible mechanism for increased binding is proposed.
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PMID:Chemical and enzymatic synthesis of multivalent sialoglycopeptides. 814 76

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.
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PMID:The synthesis of sialylated oligosaccharides using a CMP-Neu5Ac synthetase/sialyltransferase fusion. 970 65

A large-scale production system of cytidine 5'monophospho-N-acetylneuraminic acid (CMP-NeuAc) and sialyloligosaccharides was established by a whole-cell reaction through the combination of recombinant Escherichia coli strains and Corynebacterium ammonia-genes. For the production of CMP-NeuAc, two recombinant E. coli strains were generated that overexpressed the genes of CMP-NeuAc synthetase and CTP synthetase, respectively. C. ammoniagenes contributed to the formation of UTP from orotic acid. CMP-NeuAc was accumulated at 27 mM (17 g/l) after a 27-h reaction starting with orotic acid and N-acetylneuraminic acid. When E. coli cells that overexpressed the alpha-(2-->3)-sialyltransferase gene of Neisseria gonorrhoeae were put into the CMP-NeuAc production system, 3'-sialyllactose was accumulated at 52 mM (33 g/l) after an 11-h reaction starting with orotic acid, N-acetylneuraminic acid, and lactose. Almost no oligosaccharide byproducts other than 3'-sialyllactose were observed after the reaction. The production of 3'-sialyllactose at a 5-l jar fermenter scale was almost the same as that at a beaker scale, which indicated the high potential of the 3'-sialyllactose production on an industrial scale.
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PMID:Large-scale production of CMP-NeuAc and sialylated oligosaccharides through bacterial coupling. 1077 62

Neisseria meningitidis trisaccharide [GlcNAc[(1-->3)Galbeta(1-->4)Glc-R], tetrasaccharide [Galbeta(1-->4)GlcNAcbeta(1--> 3)Galbeta(1-->4)Glc-R], and a pentasaccharide [Neu5Acalpha(2-->3)Galbeta(1-->4)GlcNAcbeta(1-->3)G albeta(1-->4)Glc-SPh] were prepared via conventional chemical synthesis, polymer-supported synthesis, and chemoenzymatic methods, starting from D-lactose. The polymer polyethyleneglycol monomethylether (MPEG) and the linker dioxyxylene (DOX) were used with a lactose-bound acceptor to improve the purification process. Several enzymes (LgtA, GalE-LgtB fusion, and CMP-Neu5Ac synthetase/sialyltransferase fusion) were used for syntheses of these oligosaccharides. Excellent stereo- and regioselectivities as well as high yield (> 90% from Gal(1-->4)Glc-SPh) of the pentasaccharide were obtained. Both of the convenient processes are suitable for efficient preparation of target oligosaccharides.
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PMID:Polymer-supported and chemoenzymatic synthesis of the Neisseria meningitidis pentasaccharide: a methodological comparison. 1100 72

In conclusion, either enzymatic or chemical approaches have their unique features and unavoidable disadvantages. Enzyme-catalyzed sialylations provide the desired sialo-glycosidic linkages in the two enzyme reactions (CMP-NeuAc synthetase and sialyltransferase) with exclusive stereoselectivity and high yield as long as the required sialyltransferase is available. High substrate specificity of the two enzymes is a limitation so that many unnatural glycoconjugates cannot be prepared enzymatically. As for chemical glycosylations of sialic acids, it is possible to introduce any modification in sialyl donor and acceptor, in addition to create special sugar linkages. Nevertheless, reducing the number of reaction steps (for preparing both donors and acceptors of glycosylation), and enhancing stereoselectivity, as well as reaction yield are still problems to be overcome.
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PMID:Enzymatic and chemical approaches for the synthesis of sialyl glycoconjugates. 1453 1

A chemo-enzymatic synthesis of [(5-acetamido-9-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylonic acid)-(2-->3)-O-(beta-D-galactopyranosyl)-(1-->3)-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)]-l-serine acetate (1) has been accomplished by a regioselective chemical acetylation of Neu5Ac (2) to give 9-O-acetylated sialic acid 3, which was enzymatically converted into CMP-Neu5,9Ac(2) (4) employing a recombinant CMP-sialic acid synthetase from Neisseria meningitis [EC 2.7.7.43]. The resulting compound was then employed for the enzymatic glycosylation of the C-3' hydroxyl of chemically prepared glycosylated amino acid 10 using recombinant rat alpha-(2-->3)-O-sialyltransferase expressed in Spodooptera frugiperda [EC 2.4.99.4] to give, after deprotection of the N(alpha)-benzyloxycarbonyl (CBz)-protecting group of serine, target compound 1. The N(alpha)-CBz-protected intermediate 11 can be employed for the synthesis of glycolipopeptides for immunization purposes.
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PMID:Chemo-enzymatic synthesis of C-9 acetylated sialosides. 1850 39

Sialic acids are abundant nine-carbon sugars expressed terminally on glycoconjugates of eukaryotic cells and are crucial for a variety of cell biological functions such as cell-cell adhesion, intracellular signaling, and in regulation of glycoproteins stability. In bacteria, N-acetylneuraminic acid (Neu5Ac) polymers are important virulence factors. Cytidine 5'-monophosphate (CMP)-N-acetylneuraminic acid synthetase (CSS; EC 2.7.7.43), the key enzyme that synthesizes CMP-N-acetylneuraminic acid, the donor molecule for numerous sialyltransferase reactions, is present in both prokaryotes and eukaryotic systems. Herein, we emphasize the source, function, and biotechnological applications of CSS enzymes from bacterial sources. To date, only a few CSS from pathogenic bacterial species such as Neisseria meningitidis, Escherichia coli, group B streptococci, Haemophilus ducreyi, and Pasteurella hemolytica and an enzyme from nonpathogenic bacterium, Clostridium thermocellum, have been described. Overall, the enzymes from both Gram-positive and Gram-negative bacteria share common catalytic properties such as their dependency on divalent cation, temperature and pH profiles, and catalytic mechanisms. The enzymes, however, can be categorized as smaller and larger enzymes depending on their molecular weight. The larger enzymes in some cases are bifunctional; they have exhibited acetylhydrolase activity in addition to their sugar nucleotidyltransferase activity. The CSSs are important enzymes for the chemoenzymatic synthesis of various sialooligosaccharides of significance in biotechnology.
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PMID:Bacterial CMP-sialic acid synthetases: production, properties, and applications. 1871 69


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