Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MONOSACCHARIDES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37Linked to original sources
PubMed1983

Competitive inhibition of the inverting beta-xylosidase of Bacillus pumilus 12 by monosaccharide derivatives of different structural and conformational types. A possible natural substrate.

The title enzyme is competitively inhibited by compounds, for example alpha-D-xylopyranosylpyridinium salts and 1,6-anhydro-D-glucopyranose, for which the normal 4C1 conformation of the xylopyranose ring is precluded. It is competitively inhibited by compounds, for example beta-D-xylopyranosylpyridinium salts and 1,6-anhydro-L-idopyranose, for which the 1C4 conformation is precluded, and which have no accessible conformations in common with the first set of inhibitors. It is also competitively inhibited by alpha-L-arabinofuranosides. Inhibition by 1,6-anhydroglucopyranose, 1,6-anhydro-L-idopyranose and L-arabinono-gamma-lactone is competitive with respect to each other. alpha-D-Xylopyranosyl fluoride is not a detectable substrate, by itself or in the presence of a representative of any of the three types of inhibitor. On the basis of these and literature data, it is proposed that the natural substrate is a hemicellulose fragment containing the D-Xylp beta (1 leads to 4)-[L-Araf alpha (1 leads to 3)]D-Xylp structure. Tentative inferences about the catalytic mechanism can also be drawn.

Bacillus↗
PubMed1990

Localization of the forskolin photolabelling site within the monosaccharide transporter of human erythrocytes.

Chemical and proteolytic digestion of intact erythrocyte glucose transporter as well as purified transporter protein has been used to localize the derivatization site for the photoaffinity agent 3-[125I]iodo-4-azido-phenethylamino-7-O-succinyldeacetylforskol in [( 125I]IAPS-forskolin). Comparison of the partial amino acid sequence of the labelled 18 kDa tryptic fragment with the known amino acid sequence for the HepG2 glucose transporter confirmed that the binding site for IAPS-forskolin is between the amino acid residues Glu254 and Tyr456. Digestion of intact glucose transporter with Pronase suggests that this site is within the membrane bilayer. Digestion of labelled transporter with CNBr generated a major radiolabelled fragment of Mr approximately 5800 putatively identified as residues 365-420. Isoelectric focusing of Staphylococcus aureus V8 proteinase-treated purified labelled tryptic fragment identified two peptides which likely correspond to amino acid residues 360-380 and 381-393. The common region for these radiolabelled peptides is the tenth putative transmembrane helix of the erythrocyte glucose transporter, comprising amino acid residues 369-389. Additional support for this conclusion comes from studies in which [125I]APS-forskolin was photoincorporated into the L-arabinose/H(+)-transport protein of Escherichia coli. Labelling of this transport protein was protected by both cytochalasin B and D-glucose. The region of the erythrocyte glucose transporter thought to be derivatized with IAPS-forskolin contains a tryptophan residue (Trp388) that is conserved in the sequence of the E. coli arabinose-transport protein.

Affinity Labels↗
PubMed1997

Network organization of cell metabolism: monosaccharide interconversion.

The structural properties of carbohydrate metabolism are being studied. The present contribution focuses mainly on those processes involving the transfer of carbon fragments among sugars. It is shown how enzymatic activities fix the way the system self-organizes stoichiometrically at the steady state. It is proven that there exists a specific correspondence between the set of all possible enzymic activities, the activity set, and the set of stoichiometrically compatible flux distributions through the pathway. On the one hand, there are enzymic activities that do not allow a stoichiometrically feasible coupling at the steady state of the reactions involved in the conversion. On the other hand, there are enzymic activities that are related to one or more flux distributions at the steady state (i.e. with one or several rate vectors respectively). For this latter group, it can be demonstrated that the structure of the system depends on other non-structural factors, such as boundary constraints and the kinetic parameters. As a consequence, it is suggested that this kind of metabolic process must be viewed as a complex reaction network instead of a sequential number of steps. Some implications of these derivations are illustrated for the particular conversion of CO2 --> C3. General remarks are also discussed within the framework of network models of cell metabolism.

Cells↗
PubMed1980

The influence of carbohydrate gelling agents on rat intestinal transport of monosaccharides and neutral amino acids in vitro.

1. In the present investigation with rings of everted rat small intestine, carbohydrate gelling agents (plant polysaccharides) such as guaran, pectin, tragacanth, carubin and carrageenan were employed to study their direct effect on intestinal absorption of alpha-methyl-D-glucoside, D-galactose, L-leucine and L-phenylalanine. 2. Inhibition was found to correlate with the viscosity of the incubation medium, a function only of the polysaccharide concentration, and was independent of other properties of the carbohydrate gelling agents. 3. Reversal of this inhibition was achieved either by washing the tissue free of polysaccharide or by raising tissue agitation. 4. Uptake kinetics in polysaccharide-containing solutions revealed a marked increase of the apparent Michaelis constant although the maximal transport capacity remained essentially unaltered. 5. Since there was no binding of the substrate by the polysaccharides under experimental conditions as judged by a membrane filtration technique, it is concluded that carbohydrate gelling agents may impair intestinal absorption by means of an increased unstirred layer resistance.

Amino Acids↗
PubMed1994

Functional reconstitution of the solubilized Arabidopsis thaliana STP1 monosaccharide-H+ symporter in lipid vesicles and purification of the histidine tagged protein from transgenic Saccharomyces cerevisiae.

Complete DNA sequences encoding the Arabidopsis thaliana STP1 monosaccharide/H+ symporter or a histidine-tagged STP1-His6 protein were expressed in baker's yeast Saccharomyces cerevisiae. Both wild-type STP1 and the recombinant his-tagged protein were located in the plasma membranes of transformed yeast cells. The C-terminal modification caused no loss of transport activity compared with the wild-type protein. Anti-STP1-antibodies were used to confirm the identity of the protein in yeast and to compare the apparent molecular weights of STP1 proteins in membrane extracts from yeast or Arabidopsis thaliana. Purified yeast plasma membranes were fused with proteoliposomes consisting of Escherichia coli lipids and beef heart cytochrome-c oxidase. Addition of ascorbate/TMPD/cytochrome-c to these fused vesicles caused an immediate formation of membrane potential (inside negative; monitored with [3H]tetraphenylphosphonium cations) and a simultaneous, uncoupler-sensitive influx of D-glucose into the energized vesicles. STP1-His6 protein is functionally active after solubilization with octyl-beta-D-glucoside, which was shown by insertion of the protein into proteoliposomes by detergent dilution and determination of the resulting transport capacity. Detergent extracts from either total membranes or plasma membranes of transgenic yeast cells were used for one-step purification of the STP1-His6 protein on Ni(2+)-NTA columns. The identity of the purified protein was checked by immunoblotting and N-terminal sequencing.

Amino Acid Sequence↗
PubMed2002

Phase transfer of monosaccharides through noncovalent interactions: selective extraction of glucose by a lipophilic cage receptor.

We have previously shown that macrotricyclic host 1a is a powerful receptor for glucopyranosyl units in the nonpolar medium of chloroform. However, the solubility properties of 1a did not permit studies of the extraction of carbohydrates from aqueous solution. This paper describes the synthesis of the new variant 1b, furnished with a highly lipophilic exterior array of 12 benzyloxy substituents. In homogeneous solution, 1b behaves much as 1a, binding n-octyl beta-d-glucoside with K(a) = 720 M(-1) in CD(3)OH/CDCl(3) (8:92). In two-phase experiments, the improved solubility of 1b allows carbohydrate extraction to be observed. Three hexoses (glucose, galactose, and mannose), two pentoses (ribose and xylose), and the two methyl glucosides are all extracted substantially into chloroform from 1 M aqueous solutions. Among the hexoses, 1b shows notable affinity and selectivity for glucose, extracting detectable amounts even from 0.1 M aqueous solutions.

Cadmium Chloride↗
PubMed2006

Structural basis for substrate binding and regioselective oxidation of monosaccharides at C3 by pyranose 2-oxidase.

Pyranose 2-oxidase (P2Ox) participates in fungal lignin degradation by producing the H2O2 needed for lignin-degrading peroxidases. The enzyme oxidizes cellulose- and hemicellulose-derived aldopyranoses at C2 preferentially, but also on C3, to the corresponding ketoaldoses. To investigate the structural determinants of catalysis, covalent flavinylation, substrate binding, and regioselectivity, wild-type and mutant P2Ox enzymes were produced and characterized biochemically and structurally. Removal of the histidyl-FAD linkage resulted in a catalytically competent enzyme containing tightly, but noncovalently bound FAD. This mutant (H167A) is characterized by a 5-fold lower kcat, and a 35-mV lower redox potential, although no significant structural changes were seen in its crystal structure. In previous structures of P2Ox, the substrate loop (residues 452-457) covering the active site has been either disordered or in a conformation incompatible with carbohydrate binding. We present here the crystal structure of H167A in complex with a slow substrate, 2-fluoro-2-deoxy-D-glucose. Based on the details of 2-fluoro-2-deoxy-D-glucose binding in position for oxidation at C3, we also outline a probable binding mode for D-glucose positioned for regioselective oxidation at C2. The tentative determinant for discriminating between the two binding modes is the position of the O6 hydroxyl group, which in the C2-oxidation mode can make favorable interactions with Asp452 in the substrate loop and, possibly, a nearby arginine residue (Arg472). We also substantiate our hypothesis with steady-state kinetics data for the alanine replacements of Asp452 and Arg472 as well as the double alanine 452/472 mutant.

Basidiomycota↗
PubMed1996

[Effect of the nature of the heteroatom of a monosaccharide derivative on its inhibitory action in relation to P-type calcium channels expressed in the Xenopus oocyte].

Our results demonstrate that saccharidic derivatives obtained by adding a C8 alkyl group through various heteroatomes (O, N or S) to a monoacetonide residue possess an inhibitory effect towards putative P-type calcium channels expressed in Xenopus oocytes. These derivatives partially and reversibly inhibit the activity these channels without changing their electrophysiological properties. Nevertheless, the derivative containing the heteroatome N also affects the fast and tetrodotoxin-sensitive sodium channel activity. Thus, only ether and thioether compounds (heteroatome O or S) can be selected for their inhibitory effect on P-type apparented calcium channels.

Animals↗