Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.99.6 (sialyltransferase)
 1,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The subcellular distribution of sialic acid was determined at the ultrastructural level using Limax flavus agglutinin (LFA). This lectin, which is specific for N-acetylneuraminic acid and N-glycolylneuraminic acid, was covalently conjugated to horseradish peroxidase (HRP). The conjugates (LFA-HRP) were applied to aldehyde-fixed, saponin-permeabilized 3T3 cells in pre-embedding labeling electron microscopy. Peroxidase label was detected in a patchy distribution at the cell surface, and in plasma-membrane-coated pits, endocytic vesicles (receptosomes), multivesicular bodies, and lysosomes. Smooth-surfaced tubular and vesicular structures, similar to those that participate in membrane recycling, were labeled. In the Golgi complex, more than half of the cisternae contained label--typically only one cisterna on the cis side was unlabeled. Heavily labeled structures of the trans Golgi included a reticular membranous system with coated regions--50-80 nm diameter vesicular or pit-like profiles and larger coated vacuoles. Smooth 200-300 nm vacuoles were labeled on the trans side of the Golgi stack. Similar structures have been previously shown to participate in the exocytosis of plasma membrane and secretory glycoproteins from the Golgi stacks. These findings identify those intracellular organelles that are functionally at the level of, or distal to, the sialyltransferase-containing membranes of the Golgi, and distinguish them from the pre-Golgi membranous structures. The LFA-HRP conjugate is an indicator for this functional trans domain of the cell, and should be applicable for ultrastructural double-label experiments as a cis versus trans marker of the exocytic pathway.
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PMID:The organelles of the trans domain of the cell. Ultrastructural localization of sialoglycoconjugates using Limax flavus agglutinin. 373 17

Carbohydrate-deficient transferrin (CDT) is now considered to be the most sensitive and specific biological marker of alcohol abuse. However, the mechanism by which chronic alcohol consumption causes an elevation of CDT levels in serum is still not understood. Therefore, we fed eight pairs of male rats a nutritionally adequate liquid diet containing either alcohol (36% of energy) or isocaloric dextrose (control) for 4 weeks, after which blood and liver samples were obtained. Serum CDT content in alcohol-treated rats increased by 45% (P < .05) in ethanol-fed animals compared with their corresponding controls. In contrast, in rats fed ethanol, the activities of sialyltransferase (ST), galactosyltransferase (GT), and N-acetylglucosamine transferase (N-AGT), which are glycosyltransferases involved in transferrin carbohydrate side chain synthesis, were diminished by 24% and 40% (P < .05), 23% and 51% (P < .05, .001), and 20% and 26% (P < .05) in total liver homogenates and Golgi fraction (GF) 1, respectively, when expressed as units/100 g body weight. These enzymes were also significantly less active in hepatic GFs 2 and 3. The depression of the transferase activities in ethanol-fed rats appeared to be due, at least in part, to enzyme inactivation by acetaldehyde, whereas ethanol itself was without effect. Similar results were obtained in humans: five alcohol abusers were found to exhibit a 23% decrease in hepatic sialyltransferase and a 41% increase in sialidase activities, respectively, when compared with three nondrinking subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Serum carbohydrate-deficient transferrin: mechanism of increase after chronic alcohol intake. 759 Jun 64

There are various approaches for improving endoradiotherapy and diagnosis with monoclonal antibodies in nuclear medicine. The known methods of site-specific labelling of biomolecules based either on reactions with sulfhydryl groups or on reactions with aldehyde groups of the oligosaccharide chains effect unwanted alterations of the biomolecules. We present a new method to introduce radioactive halogens into the oligosaccharide chains of an antibody, based on the enzymatic transfer of the labelled synthetic sialic acid derivative CMP-9-deoxy-9-salizoyl-NeuAc. It was first labelled by the iodogen-method (iodine) in yields of more than 90%. Under selected conditions it was possible to obtain di- and trihalogenated products. Then the radioactive sialic acid derivatives were transferred during 90 minutes at room temperature with 2.6-sialyltransferase from rat liver into the oligosaccharide chains of antibodies. It is necessary to use neuraminidase pretreated antibodies with an increased number of binding sites for sialic acid derivatives. Yields of about 55% were obtained for the monoiodinated sialic acid derivative. With this method we present a reasonable alternative reaction of labelled compounds with biomolecules. Studies of the immunoreactivity are now in progress.
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PMID:A new method for site-specific labelling of the oligosaccharide chain of antibodies: preliminary results. 763 60

The effects of acute ethanol intoxication on the glycoprotein metabolism of rat liver Golgi apparatus have been investigated. A marked reduction of the galactosyltransferase and sialyltransferase activities was observed in Golgi membranes 6 h after ethanol administration (6g/Kg body wt) together with the retention of glycoproteins in the hepatocyte. Methylpyrazole, an inhibitor of alcohol dehydrogenase, administrated "in vivo" (10 mg/Kg body wt) prevented the ethanol-induced inhibition of both the transferase activities. Acetaldehyde formed "in vitro" unstable and stable adducts with Golgi membrane proteins and with purified galactosyltransferase. These results suggest that the impairment of glycoprotein metabolism at the level of liver Golgi apparatus may be mediated, at least in part, through the acetaldehyde formation during ethanol oxidation.
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PMID:Acetaldehyde-induced impairment of protein glycosylation in liver Golgi apparatus. 833 19

D-Glucosamine was transformed into phenyl and 2-benzoyloxyethyl N-acetylglucosamine beta-glycosides 6a and 6b, respectively. Transformation of 6a,b into 6-O-unprotected N-acetylglucosamine derivatives 9a,b permitted the generation of an aldehyde group in the 6-position. Treatment of these intermediates with base afforded unsaturated aldehyde derivatives 10a,b, which are structural mimics of 2,3-dehydroneuraminic acid. H-Phosphonate addition to the aldehyde group and attachment of the cytidine monophosphate residue to the generated hydroxy group gave fully protected transition state analogues of cytidine monophosphate-N-acetylneuraminic acid 14a,b. Liberation of the unprotected compounds 1ah,l and 1bh,l led to excellent inhibitors of alpha(2-6)-sialyltransferase from rat liver. Variation of the protective group cleavage procedure for 14a,b led to formal loss of phosphate, thus resulting in diene derivatives (E)-/(Z)-2a,b, which also exhibited inhibitory properties.
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PMID:Efficient sialyltransferase inhibitors based on glycosides of N-acetylglucosamine. 1185 37

The high transmissibility and genetic variability of the influenza virus have made the design of effective approaches to control the infection particularly challenging. The virus surface hemagglutinin (HA) protein is responsible for the viral attachment to the host cell surface via the binding with its glycoligands, such as sialyllactose (SL), and thereby is an attractive target for antiviral designs. Herein we present the facile construction and development of two SL-incorporated chitosan-based materials, either as a water-soluble polymer or as a functional fiber, to demonstrate their abilities for viral adhesion inhibition and decontamination. The syntheses were accomplished by grafting a lactoside bearing an aldehyde-functionalized aglycone to the amino groups of chitosan or chitosan fiber followed by the enzymatic sialylation with sialyltransferase. The obtained water-soluble SL-chitosan conjugate bound HA with high affinity and inhibited effectively the viral attachment to host erythrocytes. Moreover, the SL-functionalized chitosan fiber efficiently removed the virus from an aqueous medium. The results collectively demonstrate that these potential new materials may function as the virus adsorbents for prevention and control of influenza. Importantly, these materials represent an appealing approach for presenting a protein ligand on a chitosan backbone, which is a versatile molecular platform for biofunctionalization and, thereby, can be used for not only antiviral designs, but also extensive medical development such as diagnosis and drug delivery.
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PMID:Carbohydrate-functionalized chitosan fiber for influenza virus capture. 2197 96