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)

The distribution of multiple forms of galactosyltransferase (EC 2.4.1.22) and sialyltransferase (EC 2.4.99.1) from the microsomes and Golgi complex membrane fractions of rat liver was investigated. Three fractions of Golgi membranes, namely GF1, GF2, and GF3, differing in their morphology and marker enzyme activity, were obtained. A simultaneous increase of glycosyltransferases under study was observed in fractions GF3 less than GF2 less than GF1. Using isoelectrofocusing, the presence of at least 6-8 forms of galactosyl- and sialyltransferases in the microsomes and Golgi fraction was revealed. The distribution patterns of multiple forms along the pH gradient for each membrane fraction were found to be identical. However, the ratios of highly active and low active forms were specific for each fraction. The similarity of multiple form spectra for galactosyl-and sialyltransferase suggest their tight functional interaction and a possible "en block" packing of membrane glycosyltransferases.
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PMID:[Multiple forms of glycosyltransferases in Golgi complex membrane fractions]. 641 72

Beta 1,4 galactosyl- and alpha 2,6 sialyltransferase (gal-T EC 2.4.1.22 and sialyl-T EC 2.4.99.1) sequentially elongate and terminate complex N-glycan chains of glycoproteins. Both enzymes reside in trans Golgi cisternae; their ultrastructural relationship, however, is unknown. To delineate their respective Golgi compartment(s) we conducted a double label immunofluorescent study by conventional and confocal laser scanning microscopy in HepG2, HeLa, and other cells in presence of Golgi-disturbing agents. Polyclonal, peptide-specific antibodies to human sialyl-T expressed as a beta-galactosidase-sialyl-T fusion protein in E. coli were developed and applied together with mABs to human milk gal-T. In untreated HepG2 and HeLa cells Golgi morphology identified by immunofluorescent labeling of sialyl-T and gal-T, respectively, was nearly identical. Treatment of cells with brefeldin A (BFA) led to rapid and coordinated disappearance of immunostaining of both enzymes; after BFA washout, vesicular structures reappeared which first stained for gal-T followed by sialyl-T; in the reassembled Golgi apparatus sialyl-T and gal-T were co-localized again. In contrast, monensin treatment produced a reversible swelling and scattering of gal-T positive Golgi elements while sialyl-T positive structures showed little change. Treatment with nocodazole led to dispersal of Golgi elements in which gal-T and sialyl-T remained co-localized. Treatment with chloroquine affected Golgi structures less than monensin and led to condensation of gal-T positive and to slight enlargement of sialyl-T positive structures. Sequential recovery from BFA of gal-T and sialyl-T and their segregation by monensin suggest that these enzymes are targeted to different Golgi subcompartments.
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PMID:Double immunofluorescent staining of alpha 2,6 sialyltransferase and beta 1,4 galactosyltransferase in monensin-treated cells: evidence for different Golgi compartments? 769 43

A simple preparation of the "core-II" N-acetylglucosaminyltransferase (UDP-D-GlcpNAc:beta-D-Galp-(1-->3)-alpha-D-GalpNAc (GlcNAc to GalNAc) beta-(1-->6)-GlcNAc-transferase, GlcNAcT, EC 2.4.1.102) from commercial mouse kidney acetone powder is reported. The enzyme obtained in a single step of affinity chromatography is suitable for use in preparative oligosaccharide synthesis. In conjunction with previously described preparations of beta-(1-->4)-galactosyltransferase (EC 2.4.1.22), alpha-(2-->3)-sialytransferase (EC 2.4.99.6) and alpha-(1-->3/4)-fucosyltransferase (EC 2.4.1.65), the GlcNAcT was used in the first step of a sequence which converted the disaccharide beta-D-Galp-(1-->3)-alpha-D-GalpNAc-OR into the sialyl-LeX-containing structure alpha-D-NeupAc-(2-->3)-beta-D-Galp- (1-->4)-[alpha-L-Fucp-(1-->3)]-beta-D-GlcpNAc-(1-->6)-[beta-D-Galp - (1-->3)]-alpha-D-GalpNAc-OR (5), where R = (CH2)8CO2Me. Hexasaccharide 5, thus assembled in only one week once the enzymes were prepared, was characterized by 1H and 13C NMR spectroscopy and fast-atom bombardment mass spectrometry, as were all intermediate oligosaccharides. The core II GlcNAcT thus joins the expanding repertoire of readily available reagents for the rapid assembly of oligosaccharides.
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PMID:Use of the "core-2"-N-acetylglucosaminyltransferase in the chemical-enzymatic synthesis of a sialyl-LeX-containing hexasaccharide found on O-linked glycoproteins. 810 68

The cDNAs encoding soluble forms of human beta-1, 4-galactosyltransferase I (EC 2.4.1.22), alpha-2,6-sialyltransferase (EC 2.4.99.1), and alpha-1,3-fucosyltransferase VI (EC 2.4.1.65), respectively, have been expressed in the methylotrophic yeast Pichia pastoris. The vector pPIC9 was used, which contains the N-terminal signal sequence of Saccharomyces cerevisiae alpha-factor to allow entry into the secretory pathway. The recombinant enzymes had similar kinetic properties as their native counterparts. Their identity was confirmed by Western blotting. Recombinant enzymes may be used for in vitro synthesis of oligosaccharides.
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PMID:Expression of functional soluble forms of human beta-1, 4-galactosyltransferase I, alpha-2,6-sialyltransferase, and alpha-1, 3-fucosyltransferase VI in the methylotrophic yeast Pichia pastoris. 1062 93

1. Rat liver microsomal preparations incubated in 1% Triton X-100 at 37 degrees C for 1h released about 60% of the membrane-bound UDP-galactose-glycoprotein galactosyltransferase (EC 2.4.1.22) into a high-speed supernatant. The supernatant galactosyltransferase which was solubilized but not purified by this treatment had a higher molecular weight than the serum enzyme as shown by Sephadex G-100 column chromatography. 2. The galactosyltransferase present in the high-speed supernatant was purified 680-fold by an affinity-column-chromatographic technique by using a column of activated Sepharose 4B coupled with alpha-lactalbumin. The galactosyltransferase ran as a single band on polyacrylamide gels and contained no sialyltransferase, N-acetylglucosaminyltransferase or UDP-galactose pyrophosphatase activities. 3. The purified membrane enzyme had properties similar to serum galactosyltransferase. It had an absolute requirement for Mn(2+) that could not be replaced by Ca(2+), Mg(2+), Zn(2+) or Co(2+), and was active over a wide pH range (6-8) with a pH optimum of 6.5. The apparent K(m) for UDP-galactose was 10.8mum. The protein alpha-lactalbumin modified the enzyme to a lactose synthetase by increasing substrate specificity for glucose in preference to N-acetylglucosamine and fetuin depleted of sialic acid and galactose. 4. The molecular weight of the membrane enzyme was 65000-70000, similar to that of the purified serum enzyme. Amino acid analyses of the two proteins were similar but not identical. 5. Sephadex G-100 column chromatography of the purified membrane enzyme showed a small peak (2-5%) of higher molecular weight than the purified serum enzyme. Inclusion of 1mm-epsilon-aminohexanoic acid in the isolation procedures increased this peak to as much as 30% of the total enzyme recovered. Increasing the epsilon-aminohexanoic acid concentration to 100mm resulted in no further increase in this high-molecular-weight fraction.
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PMID:Purification of membrane-bound galactosyltransferase from rat liver microsomal fractions. 1674 49