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Query: UNIPROT:P15586 (glucosamine)
 9,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A novel type of water-soluble phosphorylated glycosphingolipid was isolated from Aspergillus niger by a simple procedure involving precipitation, DEAE-cellulose chromatography and preparative t.l.c. Besides ceramide and phosphorus it contains inositol, galactose, mannose and small amounts of glucosamine.
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PMID:The occurrence of a phosphorylated glycosphingolipid in Aspergillus niger. 115 83

The identification of free glycoinositol phospholipids (GPIs) following biosynthetic labeling with [3H]glucosamine in cultured cells has been reported by several laboratories. We applied this procedure to two of the cell types used in these studies, H4IIE hepatoma cells and isolated hepatocytes, but were unable to detect a [3H]glucosamine-containing lipid that met any of the criteria for GPIs, including sensitivity to phosphatidylinositol-specific phospholipase C (PIPLC) or GPI-specific phospholipase D. Part of the difficulty in radiolabeling a GPI by this procedure was the rapid metabolic conversion of [3H]glucosamine to galactosamine and neutral or anionic derivatives. A PIPLC-sensitive radiolabeled lipid was detected only after 16 h of labeling. The water-soluble fragments released from this lipid by PIPLC corresponded largely to myo-inositol 1,2-cyclic phosphate and myo-inositol 1-phosphate, products expected from PIPLC cleavage of phosphatidylinositol or lyso-phosphatidylinositol. In an alternative approach that we introduce here, free GPIs in lipid extracts from rat liver plasma membranes were labeled by reductive radiomethylation. This procedure, which radiomethylates primary and secondary amines, has been shown to label a glucosamine residue adjacent to inositol in all GPIs characterized to date. The labeled extracts were fractionated by two-dimensional thin-layer chromatography, and a cluster of polar labeled lipids were assigned as GPIs based upon the following observations. 1) They were cleaved by PIPLC, 2) after hydrolysis in 6 N HCl, both radiomethylated glucosamine and a glucosamine-inositol conjugate were identified by cation exchange chromatography, and 3) hydrolysis in 4 M trifluoroacetic acid generated a fragment consistent with glucosamine-inositol-phosphate. These results illustrate new criteria for the identification of GPIs. The labeled GPIs also contained radiomethylated ethanolamine, another component found in GPI anchors of proteins and in mature lipid precursors of GPI anchors, suggesting that the liver plasma membrane GPIs retained considerable structural homology to GPI anchors.
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PMID:Identification of glycoinositol phospholipids in rat liver by reductive radiomethylation of amines but not in H4IIE hepatoma cells or isolated hepatocytes by biosynthetic labeling with glucosamine. 132 29

The primary aim of this study was to characterize the carbohydrate that would be supplied to the colon for fermentation under physiological conditions. Colectomized rats were fed fiber-free diets or diets containing 5% (wt/wt) gum arabic. Four (fucose, galactose, glucosamine, and galactosamine) of 11 analyzed sugars accounted for 77% of the total sugar in ileal excreta from colectomized rats fed fiber-free diets. The three sugars in gum arabic, rhamnose, arabinose, and galactose, accounted for 84% of the total sugars in gum arabic ileal excreta. Comparisons of the sugar compositions of the ileal excreta, the water-soluble fractions of the excreta, and three gel filtration fractions of the water-soluble material with those of the water-soluble fraction of rat mucosa, the acetone-soluble fraction of pancreas, and pancreatin suggested that the major source of endogenous carbohydrate is mucin. Gum arabic increased the daily excretion of the four mucin-derived sugars (fucose, galactose, glucosamine, and galactosamine) by the colectomized rats from 473 mumol per day to 634 mumol per day. We conclude that mucin is the major endogenous carbohydrate excreted from the upper gut and that gum arabic increases the amount of this endogenous carbohydrate.
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PMID:Determination of fermentable carbohydrate from the upper gastrointestinal tract by using colectomized rats. 133 9

We studied the effects of insulin on the turnover of glucosamine-labeled lipids in embryonic RAT fibroblasts that overexpressed either normal human insulin receptors or insulin receptors with defective tyrosine kinase domains. Fractionation of organic extracts by thin layer chromatography in chloroform/acetone/methanol/acetic acid/water (50/20/10/10/5, v/v) revealed two insulin-sensitive glucosaminyl lipid fractions, the TLC origin (the Rf 0.0 fraction) and a fraction that migrated with Rf 0.18-0.2 (the Rf 0.2 fraction). The insulin-sensitive molecules in both fractions could also be labeled with D-[6-3H]galactose, but not with myo-[2-3H]inositol. Methanolysis and exposure to methylamine, phospholipase A2, or phosphatidylinositol-specific PLC destroyed the insulin-sensitive lipids in the Rf 0.0 fraction, but had no effect on the Rf 0.2 fraction lipid. The Rf 0.2 fraction lipid was destroyed by endoglycoceraminidase. Insulin caused a rapid loss of label from the Rf 0.0 fraction and an equally rapid increased labeling of the Rf 0.2 fraction, with similar time courses and dependencies on insulin concentration. The turnover of both lipids exhibited the same the insulin dose-response characteristics in cultures which overexpressed insulin receptors with defective tyrosine kinase domains as in cultures that overexpressed normal human insulin receptors. This result supports the conclusions that a number of signaling pathways diverge from the insulin receptor and that not all of those pathways are regulated by the insulin receptor tyrosine kinase.
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PMID:Relationship between insulin-mediated turnover of glucosamine-labeled lipids and activity of the insulin receptor tyrosine kinase. 133 12

Aqueous phenol extraction of the lower trypanosomatid Leptomonas samueli released into the aqueous layer a chloroform/methanol/water-soluble glycophosphosphingolipid fraction. Alkaline degradation and purification by gel filtration chromatography resulted in a tetrasaccharide (phosphatidylinositol (PI)-oligosaccharide A), and a pentasaccharide (PI-oligosaccharide B), each containing 2 mol of 2-aminoethylphosphonate and 1 mol of phosphate. Nuclear magnetic resonance spectroscopy and fast atom bombardment-mass spectrometry suggested that the structure of PI-oligosaccharide A is [formula: see text] and that of PI-oligosaccharide B is as shown. [formula: see text] Both compounds contain an inositol unit linked to ceramide via a phosphodiester bridge. The major aliphatic components of the ceramide portion are stearic acid, lignoceric acid, and C20-phytosphingosine. These novel glycolipids fall within the glycosylated phosphatidylinositol (GPI) family, since they contain the core structure Man alpha (1-->4)GlcNH2 alpha (1-->6)myo-inositol-1-PO4, which is also found in the glycoinositolphospholipids and lipophosphoglycan of Leishmania spp., the L. major promastigote surface protease, the glycosylphosphatidylinositol anchor of Trypanosoma brucei variant surface glycoprotein, and the lipopeptidophosphoglycan of Trypanosoma cruzi. The glycophosphosphingolipids of Leptomonas have features in common with the glycolipids of both Leishmania and T. cruzi, resembling the former by the alpha (1-->3) linkage of mannose to the GPI core, while the 2-aminoethylphosphonate substituent on O-6 of glucosamine and the presence of ceramide in place of glycerol lipids is more reminiscent of T. cruzi. Thus these data lend some support to the hypothesis that both T. cruzi and Leishmania evolved from a Leptomonas-like ancestor.
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PMID:Structural characterization of a novel class of glycophosphosphingolipids from the protozoan Leptomonas samueli. 144 77

The crystal structure of the fully oxidized form of ascorbate oxidase (EC 1.10.3.3) from Zucchini has been refined at 1.90 A (1 A = 0.1 nm) resolution, using an energy-restrained least-squares refinement procedure. The refined model, which includes 8764 protein atoms, 9 copper atoms and 970 solvent molecules, has a crystallographic R-factor of 20.3% for 85,252 reflections between 8 and 1.90 A resolution. The root-mean-square deviation in bond lengths and bond angles from ideal values is 0.011 A and 2.99 degrees, respectively. The subunits of 552 residues (70,000 Mr) are arranged as tetramers with D2 symmetry. One of the dyads is realized by the crystallographic axis parallel to the c-axis giving one dimer in the asymmetric unit. The dimer related about this crystallographic axis is suggested as the dimer present in solution. Asn92 is the attachment site for one of the two N-linked sugar moieties, which has defined electron density for the N-linked N-acetyl-glucosamine ring. Each subunit is built up by three domains arranged sequentially on the polypeptide chain and tightly associated in space. The folding of all three domains is of a similar beta-barrel type and related to plastocyanin and azurin. An analysis of intra- and intertetramer hydrogen bond and van der Waals interactions is presented. Each subunit has four copper atoms bound as mononuclear and trinuclear species. The mononuclear copper has two histidine, a cysteine and a methionine ligand and represents the type-1 copper. It is located in domain 3. The bond lengths of the type-1 copper centre are comparable to the values for oxidized plastocyanin. The trinuclear cluster has eight histidine ligands symmetrically supplied from domain 1 and 3. It may be subdivided into a pair of copper atoms with histidine ligands whose ligating N-atoms (5 NE2 atoms and one ND1 atom) are arranged trigonal prismatic. The pair is the putative type-3 copper. The remaining copper has two histidine ligands and is the putative spectroscopic type-2 copper. Two oxygen atoms are bound to the trinuclear species as OH- or O2- and bridging the putative type-3 copper pair and as OH- or H2O bound to the putative type-2 copper trans to the copper pair. The bond lengths within the trinuclear copper site are similar to comparable binuclear model compounds. The putative binding site for the reducing substrate is close to the type-1 copper.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Refined crystal structure of ascorbate oxidase at 1.9 A resolution. 154 98

Human glycoasparaginase (N4-(beta-N-acetyl-D-glucosaminyl)-L-asparaginase, EC 3.5.1.26) hydrolyzes a series of compounds that contain L-asparagine residue with free alpha-amino and alpha-carboxyl groups. Substrates include high mannose and complex type glycoasparagines as well as those that lack the di-N-acetylchitobiose moiety, L-aspartic acid beta-methyl ester and L-aspartic acid beta-hydroxamate. The enzyme is inactive toward L-asparagine and L-glutamine and glycoasparagines containing substituted alpha-amino and/or alpha-carboxyl groups. In the presence of the acyl acceptor hydroxylamine, glycoasparaginase catalyzes the synthesis of L-aspartic acid beta-hydroxamate from aspartyl-glucosamine, L-aspartic acid beta-methyl ester, and L-aspartic acid. 13C NMR studies using 18O-labeled L-aspartic acid demonstrate that glycoasparaginase catalyzes an oxygen exchange between water and the carboxyl group at C-4 of L-aspartic acid. These results indicate that glycoasparaginase reacts as an exo-hydrolase toward the L-asparagine moiety of the substrates and the free alpha-amino and alpha-carboxyl groups are required for the enzyme reaction. The results are consistent with an L-asparaginase-like reaction pathway which involves a beta-aspartyl enzyme intermediate. Since glycoasparaginase is active toward a series of structurally different glycoasparagines, we suggest the revised systematic name of N4-(beta-glycosyl)-L-asparaginase for the enzyme.
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PMID:Substrate specificity and reaction mechanism of human glycoasparaginase. The N-glycosidic linkage of various glycoasparagines is cleaved through a reaction mechanism similar to L-asparaginase. 155 92

Rats were chronically exposed to tritiated water (3HHO) and several tritiated organic compounds [( 3H]leucine, [3H]lysine, [3H]glucose, [3H]glucosamine, [3H]thymidine and [3H]uridine) dissolved in their drinking water. An analysis of tritium in wet and dry tissues of rats at the end of 22 days' chronic exposure showed that the chemical form of the ingested tritium was more important for tritium uptake in dry tissues than in wet tissues. The concentrations of tritium in dry tissues (organically bound tritium: OBT) after the exposure to tritiated organic compounds were consistently higher than after the exposure to 3HHO. The highest concentrations of OBT were found in rats exposed to tritiated amino acids [( 3H]lysine and [3H]leucine), which were 4-9 times higher than those in rats exposed to 3HHO. The next higher concentrations of OBT were found in rats exposed to [3H]uridine. The result of radiation dose estimations at the end of chronic exposure showed that the contribution of OBT to the total dose rate was higher in the tissues of rats exposed to tritiated organic compounds than that after the exposure to 3HHO. However, the differences between the total dose rates from 3HHO and those from tritiated organic compounds were within a factor of 2.
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PMID:Incorporation and distribution of tritium in rats after chronic exposure to various tritiated compounds. 167 70

Two proposed glycosylation sites are located within T cell epitopes of rabies virus glycoprotein, namely VVEDEGCTNLSGF (VF13; amino acids 29-41) and GKAYTIFNKTLM (GM12; amino acids 312-323). To explore the effects on peptide conformation due to post-translational modifications, we synthesized glycosylated and phosphorylated versions of the two peptides and compared their structures with the native peptide using CD and FT-IR spectroscopy. After the modifications, i.e., glycosylation on Asn with one or two N-acetyl-glucosamine or glucose residues or phosphorylation on Ser, the low to medium degree of helicity of the unmodified peptides disappears as indicated by CD measurements in water-trifluoroethanol mixtures. Incorporation of one sugar moiety into either peptide resulted with a high probability in a type I (III) beta-turn formation with almost identical spectra for the different peptides. Elongation of the carbohydrate in GM12 only slightly enhanced this effect. In contrast, phosphorylation of VF13 caused distorted conformation of the peptide backbone. This novel and direct demonstration of a change in secondary structure by glycosylation (or phosphorylation) might be an important element in determining peptide antigen structure and function.
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PMID:Glycosylation of synthetic peptides breaks helices. Phosphorylation results in distorted structure. 172 74

YAC-1 cells were propagated in bioreactors in 1 l and 7.5 l volumes. The cells were metabolically labelled with D-[1-14C]galactose and D-[1-14C]glucosamine. The ganglioside fraction, purified by DEAE-Sepharose and silica gel column chromatography, showed on thin layer chromatography four major bands with mobilities between GM1 and GD1a. Gangliosides, obtained by further purification steps including high performance liquid chromatography on silica gel 60 columns with a gradient system of isopropanol:hexane:water, and preparative high performance TLC were characterized by (1) immunostaining of corresponding asialogangliosides obtained by mild acid hydrolysis and neuraminidase treatment and (2) fast atom bombardment mass spectrometry of native and permethylated samples and methylation analysis of GM1b ganglioside. As well as small amounts of GM2 and GM1, the major gangliosides found in the complex mixture were GM1b and GalNAc-GM1b. The structural heterogeneity of these gangliosides was caused by (a) substitution of the ceramide moiety by fatty acids of different chain length and degree of unsaturation (C16:0, C24:0, C24:1) and (b) N-substitution of the sialic acid moieties with either acetyl or glycolyl groups. Disialogangliosides were detected only in low amounts and will be the subject of further investigation. A polyclonal chicken antiserum was raised against IVNeuAc-GgOse5Cer. The antiserum was highly specific for gangliosides (IVNeuAc and IVNeuGc) and asialogangliosides with a GgOse5Cer backbone. No cross-reaction with GM1b or GgOse4Cer was observed.
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PMID:Structural studies of gangliosides from the YAC-1 mouse lymphoma cell line by immunological detection and fast atom bombardment mass spectrometry. 184 83


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