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)

Human factor VIII/von Willebrand factor protein containing 120 +/- 12 nmol of sialic acid and 135 +/- 13 nmol of galactose/mg of protein was digested with neuraminidase. The affinity of native factor VIII/von Willebrand factor and its asialo form for the hepatic lectin that specifically binds asialoglycoproteins was assessed from in vitro binding experiments. Native factor VIII/von Willebrand factor exhibited negligible affinity while binding of the asialo derivative was comparable to that observed for asialo-alpha1-acid glycoprotein. Incubation of asialo-factor VIII/von Willebrand factor with Streptococcus pneumoniae beta-galactosidase removed only 62% of the galactose but abolished binding to the purified hepatic lectin. When the asialo derivative was incubated with purified beta-D-galactoside alpha2 leads to 6 sialyltransferase and CMP-[14C]NeuAc, only 61% of the galactose incorporated [14C]NeuAc. From the known specificites of these enzymes, it is concluded that galactose residues important in lectin binding are present in a terminal Gal/beta1 leads to 4GlcNAc sequence on asialo-factor VIII/von Willebrand factor. The relative ristocetin-induced platelet aggregating activity of native, asialo-, and agalacto-factor VIII/von Willebrand factor was 100:38:12, respectively, while procoagulant activity was 100:100:103.
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PMID:Carbohydrate on human factor VIII/von Willebrand factor. Impairment of function by removal of specific galactose residues. 10 Apr 92

Two different sialyltransferases (EC 2.4.99.1) have been resolved from Triton X-100 extracts of porcine submaxillary glands by affinity chromatography on CDP-hexanolamine agarose. The predominant sialyltransferase of this tissue, a CMP-N-acetylneuraminate: alpha-D-N-acetylgalactosaminide alpha2 leads to 6 sialyltransferase, has been obtained in a partially purified and stable form. A less abundant but highly active enzyme, a CMP-N-acetylneuraminate: beta-D-galactoside alpha2 leads to 3 sialyltransferase, was purified over 90,000-fold to homogeneity. Chromatography of the latter enzyme on Sephadex G-200 separated two noninterconverting forms, designated A and B, with Stokes radii of 51 A and 31 A, respectively. Both forms have equal specific activity toward lactose and contain a single polypeptide with a molecular weight of about 50,000 as estimated by gel electrophoresis. Form A appears to bind 1.18 g of Triton X-100 per g of protein, or nearly an entire detergent micelle per polypeptide, while Form B binds little or no detergent. The enzymatic properties of both forms are similar (Rearick, J.I., Sadler, J.E., Paulson, J.C., and Hill, R.L. (1979) J. Biol. Chem. 254, 4444-4451) supporting the conclusion that Form A may represent the native sialyltransferase with an intact membrane-binding site, and Form B may be a large proteolytic fragment of Form A.
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PMID:Purification to homogeneity of a beta-galactoside alpha2 leads to 3 sialyltransferase and partial purification of an alpha-N-acetylgalactosaminide alpha2 leads to 6 sialyltransferase from porcine submaxillary glands. 43 96

The substrate specificity and kinetic properties of a pure sialyltransferase from bovine colostrum have been examined. The transferase appears to incorporate sialic acid into the sequence, NeuAcalpha2 leads to 6Galbeta1 leads to 4GlcNAc, which is commonly found in glycoproteins. It has a strict substrate specificity for CMP-NeuAc and forms only the alpha2 leads to 6 sialyl linkage with beta-D-galactosides. N-Acetyllactosamine (Galbeta1 leads to 4GlcNAc) and asialo-glycoproteins containing the N-acetyllactosaminyl linkage at the nonreducing ends of the oligosaccharides prosthetic groups are the best acceptor substrates. Isomers of N-acetyllactosamine with beta1 leads to 3 or beta1 leads to 6 glycosidic linkages are less than 1% as effective as acceptor substates as the beta1 leads to 4-linked isomer. Lactose (Galbeta1 leads to 4Glc) is also a poor acceptor, indicating the importance of the 2-acetamido group in the N-acetylglucosaminyl residues. The unnatural substrate beta-methyl-L-arabinopyrano-side, a five-carbon analog of beta-methyl-D-galactoside which contains no 6-hydroxyl, also acts as a poor acceptor of the transferase and the sialylated product has been partially characterized. Kinetic properties of the enzyme in the presence and absence of inhibitors suggest that the transferase has an equilibrium random order mechanism.
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PMID:Enzymatic properties of beta-D-galactoside alpha2 leads to 6 sialytransferase from bovine colostrum. 84 33

Neuraminidase substrates suitable for analysis of linkage specificity were enzymically synthesized in good yield by linking N-acetylneuraminic acid (Neup5Ac) to O-6 and O-3 of 4-nitrophenyl beta-D-galactopyranoside with beta-D-galactoside-alpha-(2----6)-sialyltransferase and beta-D-galactoside-alpha-(2----3)-sialyltransferase, respectively. By use of these substrates, a convenient colorimetric assay method was developed for the determination of linkage specificity of bacterial and viral neuraminidases. The substrates are incubated with viral or bacterial neuraminidase and subsequently treated with beta-D-galactosidase to convert the liberated 4-nitrophenyl beta-D-galactopyranoside to 4-nitrophenol. The amount of liberated 4-nitrophenol is equivalent to the amount of Neup5Ac released from the substrate, thus allowing measurement of neuraminidase activity. The results showed that bacterial and viral neuraminidases can discriminate between these two compounds, making them useful substrates for the rapid determination of neuraminidase linkage specificity.
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PMID:Synthesis of linkage-specific sialoside substrates for colorimetric assay of neuraminidases. 180 82

The following disaccharide glycosides were obtained in yields of 10-35% from the appropriate donor and acceptor glycosides by employing glycosidases as catalysts: alpha-D-Galp-(1----3)-alpha-D-GalpNAc-OEt (alpha-D-galactosidase), beta-D-Galp-(1----3)-alpha-D-GalpNAc-OEt and beta-D-Galp-(1----3)-beta-D-GalpNAc-OEtBr (beta-D-galactosidase), beta-D-GlcpNAc-(1----6)-beta-D-Galp-OMe and beta-D-GlcpNAc-(1----6)-alpha-D-Manp-OMe (beta-N-acetylglucosaminidase). With beta-D-GlcpNAc-OEtSiMe3 as the acceptor, beta-D-galactosidase gave beta-D-Galp-(1----3)-beta-D-GlcpNAc-OEtSiMe3 almost exclusively, whereas, with beta-D-GlcpNAc-OMe as the acceptor, beta-D-Galp-(1----3)-beta-D-GlcpNAc-OMe was formed in only slightly excess over teh analogous beta-(1----4)-linked glycoside. The use of beta-D-galactosidase and beta-D-galactoside 3-alpha-sialyltransferase in sequence provided a convenient route to the trisaccharide glycosides alpha-D-Neup5Ac-(2----3)-beta-D-Galp-(1----3)-alpha-D-GalpNAc-OEt, alpha-D-Neup5Ac-(2----3)-beta-D-Galp-(1----3)-beta-D-GalpNAc-OE tBr, and alpha-D-Neup5Ac-(2----3)-beta-D-Galp-(1----3)-beta-D-GlcpNAc-OMe.
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PMID:Enzymic synthesis of di- and tri-saccharide glycosides, using glycosidases and beta-D-galactoside 3-alpha-sialyl-transferase. 255 Jan 26

Heparin treatment of human teratocarcinoma cells in culture has several manifestations. Accumulation of gangliosides is greatly decreased while the content of cellular neutral glycolipids is relatively unaffected. However, synthesis of neutral glycolipids is increased and large amounts of these glycolipids are exported out of the cells into the medium. In addition, sialyltransferase activity of heparin-treated teratocarcinoma cells is significantly inhibited, accounting for the decreased cellular content of gangliosides. These studies are not intended to infer any physiological role of heparin in the regulation of glycolipid biosynthesis. However, results do show that beta-D-galactoside 2,3-sialyltransferase is a heparin-binding protein and that inhibition of the enzyme activity by heparin is linked to an alteration in the secretion of most neutral glycolipid precursors and sialyltransferase acceptors. These data suggest that in addition to its biosynthetic function, this ganglioside transferase may play a regulatory role in glycolipid secretion.
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PMID:Inhibition of ganglioside sialyltransferase activity and stimulation of neutral glycolipid exocytosis by heparin. 360 33

Regenerating rat liver microsomes contain a beta-D-galactoside alpha-(2----3)- and a 2-acetamido-2-deoxy-beta-D-glucoside alpha-(2----6)-sialyltransferase that are involved in the synthesis of the terminal alpha-NeuAc-(2----3)-beta-D-Galp-(1----3)-alpha-[NeuAc-(2----6)]-beta- D-GlcpNAc-(1----R) group occurring in human milk oligosaccharides and the glycan chains of several N-glycoproteins. Analysis by liquid chromatography and methylation of the products of sialylation obtained when lacto-N-tetraose [beta-D-Galp-(1----3)-beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4) -D-Glc] was used as a substrate in the incubations in vitro indicated that the disialylated sequence is formed for greater than 95% through the tetrasaccharide alpha-NeuAc-(2----3)-beta-D-Gal-(1----3)-beta-D-GlcNAc-(1----3)-beta-D-G al- (1----4)-D-Glc as one of two possible intermediates. This indicates that in the synthesis of the disialylated sequence the alpha-(2----3)- and the alpha-(2----6)-sialyltransferase act in a highly preferred order in which the alpha-(2----3) enzyme acts first. This order is imposed by the specificity of the alpha-(2----6)-sialyltransferase, which requires an alpha-NeuAc-(2----3)-beta-D-Gal-(1----3)-beta-D-GlcNAc-(1----R) sequence for optimal activity, and shows very low and no activity with beta-D-Gal-(1----3)-beta-D-GlcNAc-(1----R) and beta-D-GlcNAc-(1----R) acceptor structures, respectively. Results obtained with normal rat, fetal calf, rabbit and human liver, and human placenta indicated that very similar or identical sialyltransferases occur in these tissues. It is suggested that these enzymes differ from the sialyltransferases that previously had been identified in fetal calf liver and human placenta.
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PMID:Biosynthesis of disialylated beta-D-galactopyranosyl-(1----3)-2-acetamido-2-deoxy-beta-D-glucopy ran osyl oligosaccharide chains. Identification of a beta-D-galactoside alpha-(2----3)- and a 2-acetamido-2-deoxy-beta-D-glucoside alpha-(2----6)-sialyltransferase in regenerating rat liver and other tissues. 373 Nov 83

Form A of the beta-D-galactoside alpha 2----3 sialyltransferase from porcine submaxillary glands was incorporated into liposomes. Incorporation was achieved by gel filtration of the enzyme in the presence of octylglucoside-phospholipid micelles. As detergent was removed during gel filtration, liposomes (average diameter, 370 A) with bound enzyme were formed and emerged unretarded from the column. The recovery of enzyme activity in the liposomes was about 40% of the initial activity starting with as little as 9 micrograms of transferase. Chromatography on Sepharose CL6B and sucrose density gradient centrifugation confirmed the association of enzyme with liposomes. In contrast to Form A, Form B of the sialyltransferase, which lacks the proposed lipid-binding domain of Form A, cannot be incorporated into liposomes. Form A of the transferase was also incorporated into liposomes composed of phosphatidylcholine, cholesterol, and a mixture of phospholipids from the membranes of the Golgi apparatus from porcine submaxillary glands. Although the transferase was distributed about equally on the internal and external surface of the phosphatidylcholine liposomes, most of the transferase was on the external surface in liposomes containing cholesterol (72%) or in liposomes containing Golgi apparatus phospholipids (88%). The enzyme bound to phosphatidylcholine liposomes was shown by kinetic analysis to have the same activity as that found in the presence of activity-stimulating detergents such as Triton X-100. Enzyme incorporated into cholesterol-containing liposomes had the same activity. In contrast, enzyme bound to liposomes formed from the Golgi apparatus mixed phospholipids had a lower activity, but one similar to that of the transferase in Golgi apparatus membranes. These studies suggest that the composition of a biological membrane may well influence the orientation of the transferase in the membrane as well as modulate its enzymic activity.
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PMID:Reconstitution of a porcine submaxillary gland beta-D-galactoside alpha 2----3 sialyltransferase into liposomes. 405 34

A beta-D-galactoside alpha 2 leads to 6 sialyltransferase was purified 500-fold in 14% yield from 14-day embryonic chicken liver. Characterization of the product of the sialyltransferase catalysis was accomplished by separation and permethylation of double-labelled ([14C]NeuAc, [3H]Gal) oligosaccharides following their release from the glycoprotein fetuin by hydrazinolysis. The enzyme transfers NeuAc to Gal(beta 1 leads to 4)GlcNAc(beta 1 leads to)R-terminated oligosaccharides; no activity was found towards Gal(beta 1 leads to 3)GalNAc(alpha 1 leads to)R structures. The trisaccharide. NeuAc(alpha 2 leads to 6)Gal(beta 1 leads to 4)Glc, was shown to be a good inhibitor of the sialyltransferase. Kinetic investigations of the enzyme indicate it to have a sequential, random bi-bi mechanism.
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PMID:Kinetic parameters of a beta-D-galactoside alpha 2 leads to 6 sialyltransferase from embryonic chicken liver. 675 14

Exogenous asialo-glycoproteins and endogenous acceptors are both sialylated by incubating cytidine 5'-monophosphate N-[14C]acetylneuraminic acid (CMP [14C]NeuAc) with a lysate of human platelets but their respective incorporation levels vary with the divalent cation concentration. P-Nitrophenyl-beta-D-galactoside has also been demonstrated to be an acceptor of sialyl residues, and two different sialyl derivatives are synthesized according to the concentration of divalent cations. P-Nitrophenyl-beta-D-[6-3H]galactoside has been prepared by reduction with tritiated borohydride of the compound previously oxidized by galactose oxidase. Using this labelled p-nitrophenyl-beta-D-galactoside as acceptor and unlabelled CMP-NeuAc as donor, the two sialyl derivatives have been identified by methylation analysis as alpha-sialosyl-(2-3)-p-nitrophenyl-beta-D-galactoside and alpha-sialosyl-(2-6)-p-nitrophenyl-beta-D-galactoside. In addition to their different responses to divalent cation requirements, the sialyltransferase activities responsible for the synthesis of the two sialylgalactoside isomers have been clearly distinguished by their temperature and pH optimal values. They also exhibit different susceptibilities to dithioerythritol and different stabilities. These results demonstrate the presence in human platelets of two sialyltransferases: a CMP-NeuAc: galactoside (alpha 2-3)-sialyltransferase and a CMP-NeuAc: galactoside (alpha 2-6)-sialyltransferase.
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PMID:Discrimination between activity of (alpha 2-3)-sialyltransferase and (alpha 2-6)-sialyltransferase in human platelets using p-nitrophenyl-beta-D-galactoside as acceptor. 703 71


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