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)

Sialyltransferase activity has been detected in Triton X100 extracts of all examined strains of pathogenic Neisseria as well as in 17 out of 18 Neisseria lactamica isolates. The enzyme was detected both in strains able to synthesize the 4.5 kDa lipooligosaccharide (LOS) component known to be sialylated in vivo and in vitro by cytidine 5'-monophospho-N-acetylneuraminic acid, and in some strains which lack this component. Exogenous 4.5 kDa+ LOS was required to detect the sialyltransferase activity in strains which lacked the LOS component. Sialyltransferase activity in a serogroup A, L11 (4.5 kDa-) meningococcal strain sialylated exogenous purified LOS from gonococci. The meningococcal serogroup B and C strain sialyltransferases active with LOS acceptors appeared to be distinct from the sialyltransferase required for the synthesis of the meningococcal polysialic acid capsule.
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PMID:Distribution of a lipooligosaccharide-specific sialyltransferase in pathogenic and non-pathogenic Neisseria. 832 55

1. Sialyltransferase released into the medium during the incubation of rat jejunal slices in serum-free buffer, was susceptible to proteolytic degradation. Heat inactivated horse serum or its antiproteolytic heparin-binding fraction was found to be necessary in determining the activity of sialyltransferase released (Nadkarni et al., 1991). 2. In the present study, we have shown that heat inactivated rat serum (HRS) or its antiproteolytic heparin-binding fraction (HBF) had a role in determining the sialyltransferase activity released during jejunal slice incubations. 3. Galactosyltransferase was also released during incubations, but was not proteolytically degraded and the presence of HRS or HBF in incubations did not alter the levels of galactosyltransferase activity released. 4. Trypsin activity in serum-free incubation medium was higher compared to medium containing HRS. 5. Addition of serum-free medium obtained from 4 hr incubations of the jejunal slices, to medium obtained from parallel incubations done in the presence of HRS, caused inhibition of sialyl- but not galactosyltransferase activity. 6. In jejunal homogenates stored at -20 degrees C, sialyltransferase activity was decreased during 0-45 days of storage, whereas galactosyltransferase activity remained fairly stable for upto 56 days. 7. Inclusion of HRS or HBF in homogenates resulted in higher sialyl- but not galactosyltransferase activity compared to serum-free homogenate samples. 8. The results suggest that HRS or its antiproteolytic heparin-binding proteins have a role in determining the sialyltransferase activity released from the jejunal slices. In contrast galactosyltransferase released was not susceptible to proteolysis, and HRS or HBF was not required to express its activity.
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PMID:Role of antiproteolytic heparin-binding serum protein(s) in modulating the levels of sialyl- and galactosyltransferase activity released during the incubation of rat jejunal slices. 834 15

Gal beta-1,4-GlcNAc alpha 2,6-sialyltransferase (CMP-N-acetylneuraminate:beta-galactoside alpha 2,6 sialyltransferase, EC 2.4.99.1) is a glycoprotein containing carbohydrate chains of the complex type (Jamieson, J.C. (1989) Life Sci. 43, 691-697). The carbohydrate chains may be important for controlling the expression of sialyltransferase catalytic activity during transit of the enzyme from the rough endoplasmic reticulum to the Golgi complex where it is active as a membrane bound enzyme anchored to the luminal face. To study the role of the carbohydrate chains of sialyltransferase for enzyme activity, conditions were established in which the native enzyme was deglycosylated with N-Glycanase and endo F. It was found that Glycanase removed the carbohydrate chains from native sialyltransferase, but methanol or ethanol had to be present for rapid and complete deglycosylation. Presence of methanol or ethanol were not essential for removal of carbohydrate chains with endo F. There was a correlation between the loss of catalytic activity of sialyltransferase with increased deglycosylation. After deglycosylation with Glycanase for 18 h catalytic activity was largely eliminated and there was a reduction in molecular mass of about 5 kDa compared to the untreated enzyme when examined by immunoblot analysis; this reduction was identical to that found when the denatured enzyme was deglycosylated with Glycanase. At shorter times of incubation partially deglycosylated forms of the enzyme were detected. Complete deglycosylation of native or denatured sialyltransferase with endo F could not be achieved. However, incubation with endo F for 24 h resulted in a loss of catalytic activity of about 60%. Immunoblot analysis showed the presence of three forms of the enzyme corresponding in molecular mass to the native and deglycosylated enzyme and a third form corresponding to a partially deglycosylated enzyme. Sialyltransferase was also subjected to sequential treatment with exoglycosidases. Removal of NeuAc and Gal had little effect on catalytic activity, but subsequent removal of GlcNAc resulted in a significant loss in catalytic activity suggesting that the presence of the trimannose core with GlcNAc attached is important for the expression of catalytic activity. The presence of organic solvents during deglycosylation with Glycanase may be a useful method that can be applied to other glycoproteins.
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PMID:The role of the carbohydrate chains of Gal beta-1,4-GlcNAc alpha 2,6-sialyltransferase for enzyme activity. 839 96

1. Sialyltransferase is a liver Golgi membrane-bound enzyme that is released from the liver under conditions of experimental inflammation. Previous work showed that the action of a cathepsin D-like proteinase was responsible for release of the enzyme from isolated Golgi membranes. This study shows that the same enzyme is responsible for release of sialyltransferase in whole-cell systems. 2. Gal beta 1-4GlcNAc alpha 2-6sialyltransferase (EC 2.4.99.1) was secreted from slices of rat and mouse liver into the incubation medium with larger amounts of activity being secreted from slices of liver from animals suffering from experimental inflammation. 3. The presence in the incubation medium of the cathepsin D proteinase inhibitor, pepstatin A, at 10(-4) M was sufficient to inhibit the release of sialyltransferase into the medium by about 60% after a 6 hr incubation. 4. The release of albumin and alpha 1 acid glycoprotein from rat liver slices, was not affected by the presence of pepstatin A, indicating that the proteinase inhibitor did not affect the synthesis and secretion of typical secretable proteins by the liver. 5. Intraperitoneal injections of pepstatin A into mice prior to preparation of liver slices also resulted in a significant reduction of the secretion of sialyltransferase into the incubation medium. 6. The results from these studies support the idea that a cathepsin D-like proteinase is responsible for the release of sialyltransferase into the extracellular space in whole cells in the rat and the mouse.
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PMID:Evidence for the role of a cathepsin D-like activity in the release of Gal beta 1-4GlcNAc alpha 2-6sialyltransferase from rat and mouse liver in whole-cell systems. 844 97

In vivo, gonococci encounter a myriad of conditions not present in vitro. At some stages of infection and disease, gonococci may grow anaerobically, probably by using sodium nitrite as a terminal electron acceptor. Also, gonococci sialylate their lipooligosaccharide (LOS) in vivo, by using low concentrations of cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NANA) present in host tissue. This sialylation is responsible for the acquired resistance of gonococci to both normal and immune human serum. Given that gonococci grown in the absence of oxygen or in the presence of CMP-NANA probably more closely resemble gonococci grown inside a human host, we studied the serum resistance of gonococci cultivated under these conditions. In the absence of CMP-NANA, anaerobically grown (anaerobic) gonococci were somewhat less sensitive to serum killing than were aerobically grown (aerobic) gonococci. However, anaerobic gonococci grown with 6 micrograms of CMP-NANA per ml exhibited almost complete serum resistance, while aerobic gonococci required 16-fold-higher CMP-NANA concentrations to achieve significant serum resistance. Anaerobic gonococci incubated in CMP-NANA converted to serum resistance two to three times faster than did similarly treated aerobic gonococci and incorporated up to six times as much sialic acid into their LOS. Gonococci can express several different LOS molecules. Anaerobic gonococci expressed the LOS molecule that acts as an acceptor for sialic acid from CMP-NANA in greater quantity than aerobic gonococci did. Finally, Triton X-100 extracts of anaerobic gonococci contained about four times more sialyltransferase activity than did extracts of aerobic gonococci. Sialyltransferase activity in these extracts was not inhibited by oxygen or enhanced by anaerobiosis. These data indicate that anaerobic conditions lead to altered LOS biosynthesis and to induction of sialyltransferase activity in gonococci. In vivo, where decreased oxygen levels and relevant concentrations of CMP-NANA are found, gonococci could readily become resistant to killing by normal and immune human serum.
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PMID:Anaerobic growth and cytidine 5'-monophospho-N-acetylneuraminic acid act synergistically to induce high-level serum resistance in Neisseria gonorrhoeae. 847 54

Sialyltransferase activities, SAT-3 (CMP-NeuAc:nLcOse4Cer alpha 2-3sialyltransferase) and SAT-4 (CMP-NeuAc:GgOse4Cer alpha 2-3sialyltransferase), in Colo 205 cells catalyze the transfer of sialic acid to the terminal galactose of GlcNc-- and GalNAc-containing glycolipid substrates, respectively. Competition kinetic studies with nLcOse4Cer and GM1 as substrates in a sialyltransferase assay show that these two activities are catalyzed by two different catalytic entities. The two enzymes were co-solubilized with taurochlorate and resolved by DEAE--Cibacron Blue--Sepharose column chromatography into two elution peaks. The column eluent with SAT-3 activity failed to transfer sialic acid to asialo alpha(1)-acid glycoprotein, indicating that this enzyme is different from the sialyltransferase (ST3N) that synthesizes NeuAc alpha 2-3Gal linkage in asparagine-linked oligosaccharides of glycoprotein. However, SAT-3 activity can be immunoprecipitated with a polyclonal antibody produced against a protein expressed in Escherichia coli as GST-fusion protein from an ECB cDNA homolog of an alpha 2-3 sialyltransferase SAT-3 or STZ) the has been cloned from human melanoma cell and human placenta. Thus a concentration-dependent decrease in the residual SAT-3 activity relative to SAT-4 activity was observed in the supernatant after precipitation of the immune complex. Expression of SAT-3 (STZ) cDNA was also detected in Colo 205 cell by RT-PCR, followed by sequence analysis of the RT-PCR product. Characterization of the catalytic reaction products of SAT-3 and SAT-4 with thin-layer chromatography, sialidase treatment, and binding to specific antibodies indicates that both SAT-3 and SAT-4 catalyze the formation of alpha 2-3 linkage between sialic acid and terminal galactose of glycolipid substrates.
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PMID:Characterization of two glycolipid: alpha 2-3sialyltransferases, SAT-3 (CMP-NeuAc:nLcOse4Cer alpha 2-3sialyltransferase) and SAT-4 (CMP-NeuAc:GgOse4Cer alpha 2-3sialyltransferase), from human colon carcinoma (Colo 205) cell line. 861

cDNA and genomic clones encoding mouse Galbeta1, 3GalNAc-specific GalNAc alpha2,6-sialyltransferase (ST6GalNAc II) were isolated, and the structure organization of the gene was determined. The predicted amino acid sequence is 57.4% identical to the chick ST6GalNAc II sequence but 33.8% identical to the chick ST6GalNA I (GalNAc alpha2, 6-sialyltransferase) sequence. The ST6GalNAc II gene is constitutively expressed in various mouse tissues but highly expressed in lactating mammary gland and adult testis. The gene contains nine exons spanning about 25 kilobases of genomic DNA and encodes a messenger RNA of 1995 nucleotides. Primer extension and S1 nuclease protection analysis of submaxillary gland mRNA showed that the transcription of the ST6GalNAc II gene starts from 68 nucleotides upstream from the translation start site. Characterization of 5'-flanking genomic regions indicated that the Galbeta1,3GalNAc-specific GalNAc alpha2,6-sialyltransferase promoter is embedded in a G+C-rich domain and contains no TATA or CAAT box but has putative binding sites for transcription factors Sp1 and AP-2. Transient transfection experiments involving luciferase reporter genes demonstrated promoter activity in NIH3T3 cells.
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PMID:Molecular cloning and genomic analysis of mouse Galbeta1, 3GalNAc-specific GalNAc alpha2,6-sialyltransferase. 866 27

Hyperacute rejection of a porcine organ by higher primates is initiated by the binding of xenoreactive natural antibodies of the recipient to blood vessels in the graft leading to complement activation. The majority of these antibodies recognize the carbohydrate structure Gal(alphal,3)Gal (gal epitope) present on cells of pigs. It is possible that the removal or lowering of the number of gal epitopes on the graft endothelium could prevent hyperacute rejection. The Gal(alpha1,3) Gal structure is formed by the enzyme Galbeta1,4GlcNAc3-alpha-D-galactosyltransferase [alpha(1,3)GT; EC 2.4.1.51], which transfers a galactose molecule to terminal N-acetyllactosamine (N-lac) present on various glycoproteins and glycolipids. The N-lac structure might be utilized as an acceptor by other glycosyltransferases such as Galbeta1,4GlcNAc 6-alpha-D-sialyltransferase [alpha(2,6)ST], Galbeta1,4GlcNAc 3-alpha-D-Sialyltransferase [alpha(2,3)ST], or Galbeta 2-alpha-L-fucosyltransferase [alpha(1,2)FT; EC 2.4.1.691, etc. In this report we describe the competition between alpha(1,2)FT and alpha(1,3)GT in cells in culture and the generation of transgenic mice and transgenic pigs that express alpha(1,2)Fr leading to synthesis of Fucalpha,2Galbeta- (H antigen) and a concomitant decrease in the level of Gal(alpha1,3)Gal. As predicted, this resulted in reduced binding of xenoreactive natural antibodies to endothelial cells of transgenic mice and protection from complement mediated lysis.
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PMID:Reduction in the level of Gal(alpha1,3)Gal in transgenic mice and pigs by the expression of an alpha(1,2)fucosyltransferase. 869 67

A bacterial sialyltransferase, named sialyltransferase 0160, was purified from a marine bacterium that had been isolated from seawater from Sagami Bay, Kanagawa. This strain has been identified as Photobacterium damsela, and named P. damsela JT0160. Sialyltransferase 0160 was purified 688-fold to homogeneity from the crude extract of the cells with a yield of 19% using a combination of anion exchange chromatography, hydroxyapatite chromatography, gel filtration chromatography, and affinity chromatography. The purified enzyme migrated as a single band (61 kDa) on sodium dodecyl sulfate-polyacrylamide gel. This sialyltransferase was found to be a beta-galactoside alpha 2,6-sialyltransferase [EC 2.4.99.1] which catalyzes the incorporation of NeuAc from CMP-NeuAc into the galactose residue of the carbohydrate chain at position 6 on the basis of an analysis of the enzymatic reaction products with HPLC, 1H-, 13C-NMR spectroscopy, and fast atom bombardment mass spectroscopy.
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PMID:Purification and characterization of a marine bacterial beta-galactoside alpha 2,6-sialyltransferase from Photobacterium damsela JT0160. 886 51

2-Keto-3-deoxy-D- glycero -D- galacto -nononic acid (KDN) was introduced into asialotransferrin and N -acetyllactosamine (LacNAc) from CMP-KDN by using rat liver Galbeta1-->4GlcNAc alpha2, 6-sialyltransferase to form KDN-transferrin and KDN-LacNAc. These structures contain terminal KDNalpha2-->6Gal-residues, a glycotope that has not yet been described in natural glycoconjugates. KDN was transferred to all four Gal residues in asialotransferrin by this enzyme. The incorporation efficiency of KDN from CMP-KDN into asialotransferrin was about half that of Neu5Ac from CMP-Neu5Ac, based on the V max/ K m values for these donor substrates, 0.0527 min-1and 0.119 min-1, respectively. The KDNalpha2-->6Gal linkage was resistant to exosialidase treatment, in contrast to the sensitivity of the Neu5Acalpha2-->6Gal linkage. Interestingly, Sambucus sieboldiana agglutinin (SSA) was shown to prefer KDN-transferrin to the corresponding Neu5Ac-transferrin, as estimated by slot-blot analysis. The use of an alpha2,6-sialyltransferase to synthesize neoglycoproteins containing KDN has not been previously reported. Their facile synthesis using CMP-KDN and sialyltransferases with different specificities offers new possibilities to study the function of neo-KDN-glycoconjugates, and to explore their use in glycotechnology.
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PMID:Synthesis of neoglycoconjugates containing deaminated neuraminic acid (KDN) using rat liver alpha2,6-sialyltransferase. 945 Oct 37


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