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

Freshly isolated gonococci upon subculture are readily lysed by normal human serum although a few strains remain inherently resistant to the complement activity. The sensitive gonococci can be converted to serum resistance by incubation with a host derived factor referred to as cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NANA). These gonococci resist complement mediated killing due to their sialylation of an epitope structure on a component of lipo-oligosaccharide (LOS). In the present study, the kinetics of conversion to serum resistance by the action of sialyltransferase (STase) in Neisseria gonorrhoeae was followed with very low concentrations of CMP-NANA. This conversion could not be perceived at 2 x 10(-3) nmol.ml-1 but was fully attainable from 8 x 10(-3) to 2 x 10(-2) nmol.ml-1 CMP-NANA. When pretreated up to 100 min in presence of the very low concentration of 2 x 10(-3) nmol.ml-1, a potentiating effect on the conversion of gonococci by 2 x 10(-2) nmol.ml-1 was observed in relation to the time of preincubation. This action was abolished after exposure to a subinhibitory concentration of chloramphenicol (0.5 microgram.ml-1). The gonococci recovered their ability to convert to serum resistance following adequate washing. The potential for increase in STase activity should be of interest for understanding the conversion from a serum sensitive to a serum resistance state.
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PMID:Kinetics of conversion of Neisseria gonorrhoeae to resistance to complement by cytidine 5'-monophospho-N-acetyl neuraminic acid. 777 96

The developmental expression of the alpha 2,6- and alpha 2,8-linked sialic acid (Sia) residues in trout egg polysialoglycoproteins (PSGPs) was studied by correlating the temporal expression of these sugar residues, and the prerequisite sialyltransferases responsible for their synthesis, during oogenesis. The following new findings are reported. 1) Disialylated glycoproteins were identified in ovaries 4-6 months prior to ovulation. Three months prior to ovulation, a second more highly sialylated glycoprotein appeared. Structural studies confirmed that the two glycoproteins were discrete molecular species, designated PSGP(low Sia) and PSGP(high Sia), which differed only in their Sia content. PSGP(low Sia) contained mostly disialyl (Sia alpha 2,8-Sia alpha 2,6-) side chains, whereas PSGP(high Sia) contained alpha 2,8-linked oligo/polySia side chains ranging in length from 2 to over 20 Sia residues. The average degree of polymerization ([DP]av) was 6. 2) Biosynthetic studies using CMP-[14C]Neu5Ac indicated that three sialyltransferase activities were responsible for synthesis of the polysialyl residues of PSGPs: (i) alpha-N-acetylgalactosaminide alpha 2,6-sialyltransferase (alpha 2,6-ST), which catalyzed formation of the Sia residues alpha 2,6-linked to the proximal GalNAc residues in asialo-PSGP; (ii) alpha 2,6-sialoside alpha 2,8-sialyltransferase (alpha 2,8-ST or "initiase"), which catalyzed transfer of the first alpha 2,8-Sia residue to the alpha 2,6-linked Sia residue; and (iii) an alpha 2,8-polysialyltransferase (alpha 2,8-polyST or "polymerase"), responsible for synthesis of the alpha 2,8-linked poly/oligo Sia chains in PSGP(high Sia). Expression of these enzyme activities increased in accordance with the developmental appearance of each PSGP. 3) Structural characterization of the [14C]Sia-labeled side chains of each PSGP at different stages of development confirmed that synthesis of the disialyl unit containing a single alpha 2,8-Sia residue occurred before alpha 2,8-polysialylation. 4) In ovaries, 96% of the sialyltransferase activities were found in the Golgi-derived immature cortical vesicles or as soluble enzymes released from the fragile vesicles. Less than 4% of the activities were localized in the membrane (Golgi) fraction. In mature eggs, the sialyltransferases were also detected as soluble enzymes, and within the cortical vesicles.
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PMID:Developmental expression of trout egg polysialoglycoproteins and the prerequisite alpha 2,6-, and alpha 2,8-sialyl and alpha 2,8-polysialyltransferase activities required for their synthesis during oogenesis. 814 14

We re-evaluated the differences between the sugar moieties of liver and bone alkaline phosphatases (ALPs). Sialic acid was added to ALP sugar moieties by alpha 2,3- or 2,6-sialyltransferase treatment of the asialo-form ALP (neuraminidase-treated ALP). Asialo-bone ALP was converted to a liver-like ALP by the 2,6-sialyltransferase treatment. The resulting liver-like ALP was less susceptible to neuraminidase than non-treated bone ALP, but was still labile to heat exposure at 56 degrees C like non-treated bone ALP. However, after the O-linked sugar moiety had been released by additional treatment with O-glycanase the liver-like ALP became more heat stable at 56 degrees C, like non-treated liver ALP. Non-treated liver ALP reacted specifically with anti-liver ALP monoclonal antibody, and non-treated bone ALP reacted with both anti-liver and anti-bone ALP antibodies. The asialo-bone ALP still reacted with anti-bone ALP antibody, whereas the asialo-form liver ALP showed little, if any, reaction with anti-liver and anti-bone ALP antibodies. Neuraminidase and O-glycanase-treated bone ALP reacted less with anti-bone ALP antibody. After O-glycanase treatment, bone ALP molecules deprived of an O-linked sugar moiety had a molecular size and heat stability similar to liver ALP. The difference between liver and bone ALP molecules may be due not only to their manner of sialic acid linkage but also to the attachment of the O-linked sugar moiety.
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PMID:Differences between the sugar moieties of liver- and bone-type alkaline phosphatases: a re-evaluation. 815 49

A sensitive assay for sialyltransferase (STase activity extracted from gonococci with 0.5% Triton X100 was developed. Enzyme activity was optimal in the pH range 5.8-8.0 and was strongly inhibited by CMP, CDP and CTP, but not by other nucleotides, 10 mM Mg2+, Zn2+, Ca2+ or Mn2+, or by 18 mM EDTA. More than 90% of the activity was lost after 30 s at 67 degrees C. The apparent Vmax and apparent Km of the STase for cytidine 5'-monophospho-N-acetylneuraminic acid were 1.7 nmol of NANA incorporated/min/mg protein and 5.3 microM, respectively.
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PMID:Detection and some properties of the sialyltransferase implicated in the sialylation of lipopolysaccharide of Neisseria gonorrhoeae. 832 54

In previous work, a low M(r) component from human blood which converts serum-sensitive gonococci to resistance was shown to be indistinguishable from cytidine 5'-monophospho-N-acetyl neuraminic acid (CMP-NANA) by seven criteria. However, the presence of CMP-NANA was not proved by physicochemical methods. Purified, high M(r) fractions from human blood cells, which confer serum resistance on gonococci and enhance the transfer of sialyl groups from CMP-NANA to lipopolysaccharide (LPS) by a sialyltransferase in gonococcal extracts, were rechromatographed on DEAE Sepharose CL-6B. Both activities co-eluted from the column but on dialysis were found in the diffusate. After desalting the diffusate with Sephadex G10, the presence of CMP-NANA was proved by mass spectrometry. This confirmed previous work and is the first unequivocal demonstration of CMP-NANA in constituents of human blood cells.
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PMID:Identification by mass spectrometry of CMP-NANA in diffusible material released from high M(r) blood cell fractions that confers serum resistance on gonococci. 832 56

Immunochemical studies of the lipo-oligosaccharides (LOS) of the Gram-negative bacteria Neisseria gonorrhoeae and Neisseria meningitidis have revealed some interesting structural characteristics of these LOS that might relate to their roles during pathogenesis. The carbohydrate moieties of the LOS of pathogenic Neisseria mimic carbohydrates present in glycosphingolipids of human cells. Firstly, an LOS component present among a number of Neisseria species is antigenically and/or chemically identical to lactoneoseries glycosphingolipids present in human cells. The lactoneoseries LOS becomes sialylated on Neisseria gonorrhoeae when they are grown in the presence of cytidine 5'-monophospho-N-acetyl-neuraminic acid (CMP-NANA), the nucleotide sugar for sialic acid. Examination of gonococci present in exudates from males with natural infection indicates that sialylation also occurs in vivo. The mechanism for this process apparently involves a bacterial sialyltransferase scavenging available host CMP-NANA ("host-modification" of LOS) and transferring the sialic acid to the lactoneoserieslike LOS. Strains of N. meningitidis and Haemophilus influenzae also express similarly sialylated LOS suggesting that this is a common mechanism of pathogenesis among these bacteria. Additional examples of LOS that mimic other glycosphingolipid series have been identified also and the fact that multiple series can be expressed in a single population of gonococci suggests that a diverse set of LOS can be presented to the host during infection. It is possible that this diverse set of LOS serve different functions for the bacteria in various hosts and/or environments during infection.
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PMID:Lipo-oligosaccharides (LOS) of mucosal pathogens: molecular mimicry and host-modification of LOS. 833 Sep 4

During short incubations of a Golgi apparatus-enriched subcellular fraction from rat liver with UDP-[3H]GlcNAc, label is efficiently transferred to endogenous acceptors. Most of the macromolecular radioactivity is specifically released by peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase, indicating that it is mainly associated with N-linked oligosaccharides. The glycoprotein acceptors are resistant to proteases unless detergent is added in amounts greater than the critical micellar concentration. This shows that the acceptors are within the lumen of intact compartments, which have the correct topological orientation expected for the Golgi apparatus in intact cells. Structural characterization of the radiolabeled N-linked oligosaccharides shows a variety of distinct neutral and anionic species. The neutral chains include bi-, tri-, and tetra-antennary molecules with terminal beta-[3H] GlcNAc residues. In vitro sialylation shows that some of the tetra-antennary chains have beta 1,3-linked Gal residues on their unlabeled antennae. An unknown modification appears to block the action of beta-galactosidase on these galactosylated oligosaccharides. Chasing the labeling reaction with a mixtures of UDP-Gal, CMP-Neu5Ac, and adenosine 3'-phosphate,5'-phosphosulfate causes an increase in the percent of radiolabeled anionic oligosaccharides. Most of the negative charge is due to sialic acid (Sia), and some appears to be in phosphodiester-linked [3H]GlcNAc. The sialylated oligosaccharides are a mixture of bi-, tri-, and tetra-antennary species with 1-3-Sia residues, and some of the [3H]GlcNAc residues are directly covered with unlabeled Gal and Sia residues. This in vitro approach should recapitulate reactions that occur in the biosynthesis of N-linked oligosaccharides in the Golgi apparatus of the intact cell. Since the conditions during labeling do not permit inter-compartmental transport, the oligosaccharides produced should represent the biosynthetic capabilities of individual Golgi compartments. Evidence is presented for a functional association of GlcNAc transferases I, II, and alpha-mannosidase II, with separation from GlcNAc transferase IV and/or V. The structures also indicate co-compartmentalization of several GlcNAc transferase(s) with beta-galactosyltransferase(s) and sialyltransferase(s). The compartmental organization of the Golgi apparatus is discussed in light of these findings.
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PMID:Biosynthesis of oligosaccharides in intact Golgi preparations from rat liver. Analysis of N-linked glycans labeled by UDP-[6-3H]N-acetylglucosamine. 834 99

As a precursor for the chemical synthesis of sialylated oligosaccharides, the trisaccharide glycoside Neu5Ac alpha (2-8)Gal beta (1-4)GlcNAc beta (1-O)-pent-4-ene was synthesized starting from GlcNAc beta (1-O)-pent-4-ene, UDP-glucose and N-acetylneuraminic acid in a one pot reaction employing galactosyltransferase and alpha (2-6)sialyltransferase in a complete cofactor regeneration system.
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PMID:Chemoenzymatic galactosialylation with integrated cofactor regeneration. 835 24

Incubation of synthetic Man beta 1-4GlcNAc beta-OMe, GalNAc beta 1-4GlcNAc beta-OMe, Glc beta 1-4GlcNAc beta-OMe, and GlcNAc beta 1-4GlcNAc beta-OMe with CMP-Neu5Ac and rat liver Gal beta 1-4GlcNAc alpha(2-6)-sialyltransferase resulted in the formation of Neu5Ac alpha 2-6Man beta 1-4GlcNAc beta-OMe, Neu5Ac alpha 2-6GalNAc beta 1-4GlcNAc beta-OMe, Neu5Ac alpha 2-6Glc beta 1-4GlcNAc beta-OMe and Neu5Ac alpha 2-6GlcNAc beta 1-4GlcNAc beta-OMe, respectively. Under conditions which led to quantitative conversion of Gal beta 1-4GlcNAc beta-OEt into Neu5Ac alpha 2-6Gal beta 1-4GlcNAc beta-OEt, the aforementioned products were obtained in yields of 4%, 48%, 16% and 8%, respectively. HPLC on Partisil 10 SAX was used to isolate the various sialyltrisaccharides, and identification was carried out using 1- and 2-dimensional 500-MHz 1H-NMR spectroscopy.
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PMID:Action of rat liver Gal beta 1-4GlcNAc alpha(2-6)-sialyltransferase on Man beta 1-4GlcNAc beta-OMe, GalNAc beta 1-4GlcNAc beta-OMe, Glc beta 1-4GlcNAc beta-OMe and GlcNAc beta 1-4GlcNAc beta-OMe as synthetic substrates. 835 30

We have investigated the activity of CMP-Neu5Ac:Gal beta 1-3GalNAc alpha-2,3-sialyltransferase (EC 2.4.99.4) in FR3T3 cells transformed by the Ha-ras oncogene in which we have previously demonstrated the higher expression of the beta-galactosidase alpha-2,6-sialyltransferase (EC 2.4.99.1) [21]. We demonstrate that the presence of the activated ras gene decreases the activity of this specific alpha-2,3-sialyltransferase fourfold. According to the kinetic parameters and to mixing experiments, we can assume that this decreased enzymatic activity reflects a decrease in the number of active O-glycan alpha-2,3-sialyltransferase polypeptides in ras-transformed cells. However, no change in the binding of Peanut agglutinin was observed on the cell surface of ras-transformed FR3T3 suggesting that no change in the sialylation of O-glycan core 1 appeared in these cells, although the activity of the alpha-2,3-sialyltransferase was decreased.
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PMID:Sialyltransferase activity in FR3T3 cells transformed with ras oncogene: decreased CMP-Neu5Ac:Gal beta 1-3GalNAc alpha-2,3-sialyltransferase. 835 31


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