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PubMed1997

Glucosamine for psoriasis?

Amphiregulin and transforming growth factor-alpha, agonists for the epidermal growth factor receptor, are the major autocrine growth factors for cultured keratinocytes, and their substantial overexpression in psoriatic lesions suggests that they are crucial to the basal hyperplasia that characterizes psoriasis. Amphiregulin binds to heparin and related highly sulfated polysaccharides, and exogenous heparin blocks its growth factor activity, rationalizing previous reports that psoriasis responds to heparin therapy. Differentiating keratinocytes produce increased amounts of protein-bound as well as free-chain heparan sulfates, which may function physiologically as amphiregulin antagonists. By promoting keratinocyte synthesis of these heparan sulfates, glucosamine administration may inhibit amphiregulin function and thus provide therapeutic benefit in psoriasis. Concurrent ingestion of fish oil, by impeding the excessive activation of protein kinase C, may decrease keratinocyte production of amphiregulin and other autocrine growth factors, thus complementing the postulated benefits of glucosamine.

Amphiregulin↗
PubMed1998

Glucosamine in osteoarthritis and gastrointestinal disorders: an exemplar of the need for a paradigm shift.

Glucosamine, after a latent period, is rapidly developing a position in the treatment of osteoarthritis, as well as a potential therapeutic place in wound healing and gastrointestinal disorders. Although recognized for a great many years, the association of gastrointestinal disorders and arthritis has been looked on as an unexplained oddity. Could this be indicative of a common etiology in the rate-limiting production of glucosamine? Could diverse presentations and pathology be due to a common-stem biochemical defect?

Animals↗
PubMed1990

Levels of [3H]glucosamine incorporation into hyaluronic acid by fibroblasts is modulated by culture conditions.

Tissue culture conditions can modulate apparent levels of incorporation of the radiolabeled precursor [3H]glucosamine into hyaluronic acid in cells. A careful study was made on the effects of culture conditions on human skin fibroblasts. A newly described technique to measure hyaluronic acid was utilized based on incorporation of [3H]glucosamine into cetylpyridinium chloride-precipitable hyaluronidase-digestible material. The precipitate was collected on glass fiber filters using a manifold suction apparatus. A six-fold greater level of incorporation occurred in rapidly growing preconfluent than in confluent fibroblasts. Ascorbic acid stimulated incorporation with a maximum at 25 micrograms/ml. The same ascorbic acid optimum was observed for collagen prolylhydroxylation. When beta-hydroxybutyrate was used as an energy source instead of D-glucose, a 3.5-fold increase in levels was observed. All tissue-culture media examined supported comparable levels of incorporation, except for Roswell Park Memorial Institute Media-1640, in which cells had only half the level. Fetal calf serum supported high levels of incorporation in a dose-dependent manner, while newborn calf and calf sera supported much lower levels of incorporation. Under serum-free conditions, lactalbumin hydrolysate was best able to support incorporation of hyaluronic acid. In the search for mechanisms that modulate hyaluronic acid, it is critical to consider the tissue culture conditions under which incorporation of radiolabeled precursors are being examined.

3-Hydroxybutyric Acid↗
PubMed1999

The allosteric transition of glucosamine-6-phosphate deaminase: the structure of the T state at 2.3 A resolution.

BACKGROUND: The allosteric hexameric enzyme glucosamine-6-phosphate deaminase from Escherichia coli catalyses the regulatory step of N-acetylglucosamine catabolism, which consists of the isomerisation and deamination of glucosamine 6-phosphate (GlcN6P) to form fructose 6-phosphate (Fru6P) and ammonia. The reversibility of the catalysis and its rapid-equilibrium random kinetic mechanism, among other properties, make this enzyme a good model for studying allosteric processes. RESULTS: Here we present the structure of P6(3)22 crystals, obtained in sodium acetate, of GlcN6P deaminase in its ligand-free T state. These crystals are very sensitive to X-ray radiation and have a high (78%) solvent content. The activesite lid (residues 162-185) is highly disordered in the T conformer; this may contribute significantly to the free-energy change of the whole allosteric transition. Comparison of the structure with the crystallographic coordinates of the R conformer (Brookhaven Protein Data Bank entry 1 dea) allows us to describe the geometrical changes associated with the allosteric transition as the movement of two rigid entities within each monomer. The active site, located in a deep cleft between these two rigid entities, presents a more open geometry in the T conformer than in the R conformer. CONCLUSIONS: The differences in active-site geometry are related to alterations in the substrate-binding properties associated with the allosteric transition. The rigid nature of the two mobile structural units of each monomer seems to be essential in order to explain the observed kinetics of the deaminase hexamer. The triggers for both the homotropic and heterotropic allosteric transitions are discussed and particular residues are assigned to these functions. A structural basis for an entropic term in the allosteric transition is an interesting new feature that emerges from this study.

Aldose-Ketose Isomerases↗
PubMedDate not supplied

Identification and characterization of high glucose and glucosamine responsive element in the rat osteopontin promoter.

We have previously reported that high glucose stimulates osteopontin (OPN) expression via a protein kinase C-dependent pathway and a hexosamine pathway in cultured rat aortic smooth muscle cells (SMCs) [Biochem. Biophys. Res. Commun. 258 (1999) 722.]. In the present study, we carried out functional OPN promoter assays using the luciferase expression vector system in cultured rat aortic SMCs to determine a high glucose/glucosamine responsive element. An extensive deletion analysis of the 5'-flanking region of the rat OPN gene revealed that an element involved in high glucose and glucosamine responses was present within a region between -112 and -62 bp of the OPN promoter. This region is highly conserved in the rat, mouse, and human promoters and contains a number of consensus regions, including an E-box and a GC-rich region. Mutation of the E-box or the GC-rich region resulted in a significant loss of both high glucose and glucosamine responses. These results suggest that two cis-acting elements, the E-box and the GC-rich region, are involved at least partly in high glucose/glucosamine-stimulated transcription of the rat OPN gene.

Animals↗
PubMed1989

Selective labeling of the erythrocyte hexose carrier with a maleimide derivative of glucosamine: relationship of an exofacial sulfhydryl to carrier conformation and structure.

Sulfhydryl-reactive derivatives of glucosamine were synthesized as potentially transportable affinity labels of the human erythrocyte hexose carrier. N-Maleoylglycyl derivatives of either 6- or 2-amino-2-deoxy-D-glucopyranose were the most potent inhibitors of 3-O-methylglucose uptake, with concentrations of half-maximal irreversible inhibition of about 1 mM. Surprisingly, these derivatives were very poorly transported into erythrocytes. They reacted rather with an exofacial sulfhydryl on the carrier following a reversible binding step, the latter possibly to the exofacial substrate binding site. However, their reactivity was determined primarily by access to the exofacial sulfhydryl, which, as predicted by the one-site model of transport, required a carrier conformation with the exofacial substrate binding site exposed. Once reacted, the carrier was "locked" in a conformation unable to reorient inwardly and bind cytochalasin B. In intact erythrocytes the N-maleoylglycyl derivative of 2-[3H]glucosamine labeled predominantly an Mr 45,000-66,000 protein on gel electrophoresis in a quantitative and cytochalasin B inhibitable fashion. By use of changes in carrier conformation induced by competitive transport inhibitors in a "double" differential labeling method, virtually complete selectivity of labeling of the carrier protein was achieved, the latter permitting localization of the reactive exofacial sulfhydryl to an Mr 18,000-20,000 tryptic fragment of the carrier.

3-O-Methylglucose↗
PubMed1977

Addition of glucosamine and mannose to nascent immunoglobulin heavy chains.

We have investigated the process of protein glycosylation in an attempt to answer the question of whether glucosamine and mannose are added to nascent chains prior to chain completion or only to completed chains after release from the ribosome. The MPC 11 mouse plasmacytoma cell line used in these studies synthesizes a glycosylated gamma2b heavy chain which accounts for 12% of the total protein synthesis. Nascent chains were separated from completed chains by ion-exchange chromatography of solubilized ribosomes on QAE-Sephadex. Our results indicate that both glucosamine and mannose are incorporated into nascent heavy chains prior to chain completion and release from the ribosome. Gel analysis of specifically immunoprecipitated nascent chains indicates that the carbohydrate moiety can be added to the nascent heavy chains very soon after the presumptive asparaginyl glycosylation site (CH2 domain) is synthesized on the ribosome.

Cell Fractionation↗
PubMed2004

Relative susceptibilities of the glucosamine-glucuronic acid and N-acetylglucosamine-glucuronic acid linkages to heparin lyase III.

Heparin lyases are valuable tools for generating oligosaccharide fragments and in sequence determination of heparan sulfate (HS). Heparin lyase III is known to cleave the linkages between N-acetylglucosamine (GlcNAc) or N-sulfated glucosamine (GlcNS) and glucuronic acid (GlcA) as the primary sites and the linkages between GlcNAc, GlcNAc(6S), or GlcNS and iduronic acid as secondary sites. N-Unsubstituted glucosamine (GlcN) occurs as a minor component in HS, and it has been associated with various bioactivities. Here we investigate the specificity of heparin lyase III toward the GlcN-GlcA linkage using a recombinant enzyme of high purity and as substrates the partially de-N-acetylated polysaccharide of Escherichia coli K5 strain and derived hexasaccharides. The specificity of lyase III toward the GlcN-GlcA linkage is deduced by sequencing of the oligosaccharide products using electrospray mass spectrometry with collision-induced dissociation and MS/MS scanning. The results demonstrate that under controlled conditions for partial digestion, lyase III does not act at the GlcN-GlcA linkage, whereas GlcNAc-GlcA is cleaved. Even under forced conditions for exhaustive digestion, the GlcN-GlcA linkage is only partly cleaved. It is this property of lyase III that has enabled the isolation of a unique, nonsulfated antigenic determinant DeltaUA-GlcN-UA-GlcNAc from HS and from partially de-N-acetylated K5 polysaccharide. It was unexpected that pentasaccharide fragments were also detected among the digestion products of the K5 polysaccharide used. It is possible that these are products of an additional glycosidase activity of lyase III, although other mechanisms cannot be completely ruled out.

Acetylation↗
PubMedDate not supplied

A Mössbauer study of the interaction of chitosan and D-glucosamine with iron and its relevance to other metalloenzymes.

The interaction of iron with water-soluble polymer chitosan and monomer d-glucosamine is investigated by Mössbauer spectroscopy. The 4.2 K Mössbauer spectrum of Fe-water-soluble chitosan complex indicates the presence of a magnetic pattern and a quadrupole doublet, and analysis of the spectral data leads to the conclusion that an Fe(II) state is partially stabilized in this system. Fe-glucosamine (monomer of chitosan) complex, on the other hand, clearly stabilizes the Fe(II) state in the acidic pH range as evidenced from the isomer shift extracted from the Mössbauer spectra. The oxidation state of the metal ion in the complex is found to be pH dependent. Indirect evidence supporting the involvement of amino group in the bonding with the metal ion is discussed. From the analysis of the experimental data under varying experimental conditions, it is concluded that the metal ion in the complex is at least tetracoordinated and at most hexacoordinated with O/N ligands of the polymer or monomer and thus corroborates the bonding scheme proposed earlier.

Chitin↗
PubMed2006

Glucosamine conjugates of tricarbonylcyclopentadienyl rhenium(I) and technetium(I) cores.

To obtain a 99mTc glucose conjugate for imaging, double-ligand transfer (DLT) and related reactions were examined for the preparation of CpM(CO)3 (Cp = cyclopentadienyl; M = Re, Tc) complexes with pendant carbohydrates at Cp. Tricarbonyl{N-(1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-beta-D-glucopyranose)cyclopentadienyl carboxamide}rhenium(I) (1a) and tricarbonyl{N-(2-amino-2-deoxy-beta-D-glucopyranose)cyclopentadienyl carboxamide}rhenium(I) (2a) were prepared. The compounds were fully characterized by mass spectrometry, elemental analysis, IR, and NMR spectroscopy. Full assignment of the NMR spectra verified the pendant nature of the glucosamine moieties in the solution state and that 2a exists as both anomers. The solid-state structure of 2a was determined by X-ray crystallography, again confirming the pendant nature of the glucosamine, but differing from the solution state in that the beta anomer crystallized preferentially (93%). Compound 2a was determined to be a high-affinity competitive inhibitor (Ki = 330 +/- 70 microM) of the glucose metabolism enzyme hexokinase, demonstrating that it retains certain biological activity. The 99mTc analogues 1b and 2b were prepared in moderate radiochemical yields by means of the single-ligand transfer (SLT) route, which is more pertinent to radiopharmaceutical synthesis.

Glucosamine↗
PubMed2005

Glucosamine-glycerophospholipids that activate cell-matrix adhesion and migration.

Two new analogues derived from the platelet activating factor (PAF), containing glucosamine instead of the acetyl group, were synthesized, and their effect on the human keratinocyte cell line HaCaT was evaluated with respect to cytotoxicity, proliferation, adhesion, and migration. Starting with (R)-1,2-isopropylideneglycerol (3), the glycosylation acceptor 1-O-octadecyl-3-O-tert-butyldimethylsilyl-sn-glycerol (6) was synthesized in three steps. Glycosylation of 6 with the already known O-(3,4,6-tri-O-acetyl-2-deoxy-2-dimethylmaleimido-beta-D-glycopyranosyl)trichloracetimidate gave 1-O-octadecyl-2-O-(3',4',6'-tri-O-acetyl-2'-deoxy-2'-dimethylmaleimido-beta-D-glucopyranosyl)-3-O-tert-butyldimethylsilyl-sn-glycerol (7). After removing the (tert-butyldimethyl)silyl (TBDMS) group with FeCl3x6H2O, phosphoryl choline was introduced, yielding [1-O-octadecyl-2-O-(2'-deoxy-2'-dimethylmaleimido-beta-D-glucopyranosyl)-sn-glycero(3)]phosphorylcholine (2) (glucosimide-PAF). pH controlled cleavage of the amino protection group gave [1-O-octadecyl-2-O-(2'-deoxy-2'-amino-beta-D-glucopyranosyl)-sn-glycero(3)]phosphorylcholine hydrochloride (1) (glucosamine-PAF). 2 inhibited proliferation of HaCaT cells by 26% at nontoxic concentrations, while 1 increased the proliferation rate by 30% at low concentrations. At higher concentrations, both compounds showed cytotoxic properties with LD50 = 30 micromol/L (1) and LD50 = 5-6 micromol/L (2). Both 1 and 2 were potent promoters of cell adhesion and migration of HaCaT cells.

Antineoplastic Agents↗
PubMed2006

A new approach to the neoglycopeptides: synthesis of urea- and carbamate-tethered N-acetyl-D-glucosamine amino acid conjugates.

A novel approach to the synthesis of Fmoc-protected neoglycopeptide building blocks is described. Oxidation of N-acetyl-D-glucosamine isonitrile afforded the corresponding highly reactive glycopyranosyl isocyanate, which reacted with amino acid derivatives to furnish the corresponding urea- and carbamate-tethered Fmoc-protected N-acetyl-D-glucosamine amino acid conjugates in good yields. [reaction: see text]

Amino Acids↗
PubMed1968

The determination of glucosamine and galactosamine in some glycoproteins by radioisotope dilution.

1. The principle of radioisotope dilution was applied on a semi-micro scale to the determination of glucosamine and galactosamine in some glycoproteins, such as immunoglobulins, a urinary glycoprotein and blood-group-specific substances. 2. The glycoprotein was hydrolysed in the presence of [1-(14)C]glucosamine or [1-(14)C]galactosamine or both. The amino sugars were made to react with naphthyl isothiocyanate and the products formed were isolated by the method of Scott (1962). The specific radioactivities determined from liquid-scintillation counting and the extinction at 240mmu or 222mmu were used to calculate the content of amino sugars in the protein analysed. 3. Where the values could be compared with those found by other workers, differences were in general not very great. The advantages of the method are that high concentrations of acid can be employed and undesirable side reactions, which may occur with the free sugars, do not affect the results. A potential source of error of the method is discussed.

Carbon Isotopes↗
PubMed1971

Biosynthesis of liver membranes. Incorporation of ( 3 H)leucine into proteins and of ( 14 C)glucosamine into proteins and lipids of liver microsomal and plasma-membrane fractions.

1. The smooth-and rough-microsomal and the light and heavy plasma-membrane fractions of mouse liver homogenates were prepared and characterized by using biochemical markers. 2. The hexosamine/protein ratio was threefold higher in the plasma membranes than in the smooth-microsomal fraction. Glucosamine was bound only to protein, and galactosamine was attached mainly to lipids. 3. [(3)H]-Leucine and [(14)C]glucosamine were injected into animals and the rates of incorporation of radioactivity into the fractions were determined. Both precursors were rapidly incorporated into the microsomal fractions, but plasma membranes showed a slower rate of synthesis which reached a maximum at 2-4h after intravenous administration. 4. The light- and heavy-plasma-membrane fractions showed similar patterns of incorporation, and therefore a precursor-product relationship appears unlikely. 5. Plasma membranes, especially the light subfraction, showed appreciable incorporation of hexosamine into chloroform-methanol-soluble components which were shown to be mainly glycolipids. 6. The results indicate that liver plasma-membrane proteins and glycoproteins are synthesized at similar rates. However, glycolipid synthesis in plasma membranes occurred more rapidly.

Animals↗
PubMed1986

Trypanosoma brucei brucei variant surface glycoprotein contains non-N-acetylated glucosamine.

The C-terminal amino acid of the variant surface glycoprotein of the parasitic protozoan Trypanosoma brucei brucei is glycosylated and the oligosaccharide has been shown to contain glucosamine. By acid hydrolysis, HNO2 deamination and 1H-n.m.r. studies we have demonstrated that the amino group of this glucosamine is not N-acetylated and is most probably unmodified.

Acetylation↗
PubMed1998

Chondrocyte-mediated catabolism of aggrecan: aggrecanase-dependent cleavage induced by interleukin-1 or retinoic acid can be inhibited by glucosamine.

A rat chondrosarcoma cell line and bovine cartilage explants have been used to study the control of aggrecan degradation by chondrocytes treated with interleukin-1 (IL-1) or retinoic acid (RA). Aggrecan fragment analysis with anti-neo-epitope antibodies suggests that aggrecanase (an as yet unidentified enzyme) is the only aggrecan-degrading proteinase active in these cultures. With rat cells, aggrecanase converts the aggrecan core protein into two major G1-domain-bearing products (60 kDa with a C-terminal Glu-373, and 220 kDa with a C-terminal Glu-1459). Both products were quantified on a standardized Western analysis system with a G1-specific antibody. Immunoblots were analysed by scanning densitometry and the sensitivity, linearity and reproducibility of the assay were established. With rat cells the aggrecanase response to IL-1 was optimal at about 2 mM glutamine, but was progressively inhibited at higher concentrations, with about 90% inhibition at 10 mM glutamine. Such inhibition by glutamine was not, however, observed with bovine explants. On the other hand, marked inhibition of aggrecanase-dependent cleavage was observed with both rat cells and bovine explants when d(+)-glucosamine was included at concentrations above 2 mM. Inhibition was apparently not due to cytotoxicity or interference with IL-1 signalling, since biosynthetic activity was not inhibited and inhibition of the aggrecanase response was also obtained when RA was used as the catabolic stimulator. Possible mechanisms for the inhibition of the aggrecanase response by glucosamine in chondrocytes treated with IL-1 or RA are discussed.

Aggrecans↗
PubMed2002

Endothelin-stimulated glucose uptake: effects of intracellular Ca(2+), cAMP and glucosamine.

Endothelin-1 (ET-1) is a 21-amino-acid peptide that binds to G-protein-coupled receptors to evoke biological responses. Previously we have shown that ET-1 stimulates glucose uptake in 3T3-L1 adipocytes and neonatal rat cardiomyocytes, but the mechanism is not completely understood. ET-1 is known to modulate intracellular Ca(2+) and cAMP levels. Depletion of intracellular Ca(2+) by treating 3T3-L1 adipocytes with EDTA and 1,2-bis(2-amino-5-methylphenoxy)ethane-N,N,N',N'-tetra-acetic acid tetra-acetoxymethyl ester (MAPTAM) did not have a significant effect on ET-1-induced glucose uptake. Forskolin, a potent stimulator which stimulates adenylate cyclase and increases the intracellular cAMP level, partially inhibited insulin-stimulated glucose uptake in 3T3-L1 cells, but had no significant impact on the effect of ET-1. Forskolin also did not show an effect on the tyrosine phosphorylation of a 75 kDa protein induced by ET-1. Glucosamine treatment causes insulin resistance in cells, possibly by entering the hexosamine biosynthetic pathway. In neonatal rat cardiomyocytes, glucosamine treatment blocked both insulin and ET-1-stimulated glucose uptake and also eliminated the translocation of IRAP, an aminopeptidase in GLUT4-containing vesicles, from the cytoplasm to the plasma membrane. These results suggest that ET-1-induced glucose uptake is independent of its effects on modulating intracellular Ca(2+) and cAMP levels, but is likely linked to the hexosamine biosynthetic pathway.

3T3 Cells↗