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Query: CAS:54166-09-5 (hexitol)
 168 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Purified bovine hepatic fructose-1,6-diphosphatase, which exhibits maximal activity at neutral pH, is competitively inhibited by several analogs of its substrate, fructose 1,6-diphosphate. These include glucose 1,6-diphosphate (Ki = 9.4 X 10(-5) M), hexitol 1,6-diphosphate (Ki = 2.3 X 10(-4) M), and 2,5-anhydro-D-mannitol 1,6-diphosphate (Ki = 3.3 X 10(-8) M), and 2,5-anhydro-D-glucitol 1,6-diphosphate (Ki = 5.5 X 10(-7) M). The Ki values for both 2,5-anhydro-D-mannitol 1,6-diphosphate and 2,5-anhydro-D-glucitol 1,6-diphosphate are lower than the Km of 1.4 X 10(-6) M for fructose 1,6-diphosphate. Since 2,5-anhydro-D-mannitol 1,6-diphosphate is an analog of the beta anomer of fructose 1,6-diphosphate and 2,5-anhydro-D-glucitol 1,6-diphosphate is an analog of the alpha anomer, the lower Ki for the mannitol analog may indicate that the beta anomer of fructose 1,6-diphosphate, which predominates in solution, is the true substrate. The substrate analog 1,5-pentanediol diphosphate inhibits slightly (K0.5 = 5 X 10(-3) M), but 1,4-cyclohexyldiol diphosphate does not. The Ki for product inhibition by sodium phosphate is 9.4 X 10(-3) M. 2,5-Anhydro-D-mannitol 1,6-diphosphate and alpha-D-glucose 1,6-diphosphate are substrates at pH 9.0, but not at pH 6.5.
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PMID:Inhibition of bovine hepatic fructose-1,6-diphosphatase by substrate analogs. 0 47

The transport systems (enzymeII-complexes of the PEP-dependent sugar:phosphotransferase system) coded for in the mtl and in the gut (srl) operon of E. coli K12 have been shown to be the pacemaker enzymes in the catabolism of the two hexitols D-mannitol and D-glucitol, respectively. As for other pacemaker enzymes their activity is regulated in a complex way: (i) via competitive inhibition by analogues. (ii) via non-competitive (feedback) inhibition by the simultaneous, rapid uptake of a number of structurally related or non-related carbohydrates, regardless if these are transported by group translocation, active transport or facilitated diffusion. This type of inhibition is strongly reinforced, if the inhibitory carbohydrates are converted efficiently into hexose-phosphates at the same time. Among these, predominantly D-fructose-6-P seems to act as a feedback inhibitor for the hexitol specific enzymeII-complexes: (iii) inhibition of hixitol-phosphate accumulation by D-glucose-6-P. The influence of additional parameters (PEP level, P approximately HPr level) and indications for the existence of further mechanisms controlling the activity of hexitol and other carbohydrate transport systems will be discussed, as will be the part the inhibitory mechanisms described above play in the phenomena of transient repression and inducer exclusion.
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PMID:Analysis of regulatory mechanisms controlling the activity of the hexitol transport systems in Escherichia coli K12. 36 87

A particulate enzyme preparation prepared from the intimal layer of pig aorta catalyzed the transfer of mannose from mannosyl-phosphoryl-polyprenol (MPP) into a series of oligosaccharides that were linked to lipid. The reaction required detergent with Triton X-100 and NP-40 being best at a concentration of 0.5%. Several other detergents were inactive or only slightly active. The pH optima for this activity was about 7 to 7.5 in Tris buffer and the apparent Km for MPP was about 2 x 10(-7) M. The reaction was not stimulated by the addition of divalent cation and, in fact, was inhibited by the high concentrations of cation. The addition of EDTA did not inhibit the transfer of mannose from MPP and was somewhat stimulatory. The transferase(s) activity was "solubilized" from the particles by treatment with Triton X-100. This solubilized enzyme still formed a series of lipid-linked oligosaccharides from either MPP or GDP-mannose. The oligosaccharides were released from the lipid by mild acid hydrolysis and were separated by paper chromatography. Some five or six radioactive oligosaccharides were formed from either MPP or from GDP-mannose and these oligosaccharides had similar mobilities upon paper chromatography. However, MPP was a better donor for the larger oligosaccharides (i.e. those containing 8, 9, or 10 sugar residues), whereas GDP-mannose was better for formation of the oligosaccharide containing 7 sugar residues. In the presence of EDTA and detergent no MPP was formed from GDP-mannose, but radioactivity was still incorporated into the lipid-linked oligosaccharides. Under these conditions essentially all of the radioactivity was in the oligosaccharide containing 7 sugar residues. Since much of this activity could be released as mannose by acetolysis, GDP-mannose may be the direct mannosyl donor for formation of 1 leads to 6 branches. Oligosaccharides 7, 8, 9, and 10 were isolated and partially characterized in terms of their molecular weights, sugar composition, susceptibility to alpha-mannosidase, and 14C products formed by acetolysis and periodate oxidation. The molecular weights ranged from 1310 for oligosaccharide 7 to 1750 for oligosaccharide 10. Hydrolysis of each oligosaccharide and reduction with NaB3H4 gave the expected ratio of [3H]hexitol to [3H]hexosaminitol based on the molecular weight of the oligosaccharide. However, the hexitol fraction contained [3H]mannitol and [3H]glucitol. Since the amount of radioactivity in glucitol was 2 to 4 times that in mannitol and since only glucosaminitol was found in the amino sugar peak, it seems likely that each 14C-oligosaccharide was contaminated with an unlabeled oligosaccharide of equal molecular weight containing glucose and GlcNAc. Acetolysis of the 14C-oligosaccharides gave rise to 14C peaks of mannose, mannobiose, and mannotriose. In the larger oligosaccharides, most of the radioactivity was in mannobiose whereas in oligosaccharide 7 most of the radioactivity was in mannose...
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PMID:Enzymatic transfer of mannose from mannosyl-phosphoryl-polyprenol to lipid-linked oligosaccharides by pig aorta. 40 91

An acidic lipid fraction isolated from pig liver (Forsee, W. T. & Elbein, A.D. (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 2574-2578) stimulated the incorporation of mannose from GDP-[14C]mannose into lipid-linked oligosaccharides using a particulate enzyme fraction from maturing cotton bolls. This lipid fraction did not stimulate mannose incorporation into the mannosylphosphorylpolyprenol. The 14C-oligosaccharides, formed in the presence or absence of the pig liver "acceptor" lipid, were released from the lipid-linked oligosaccharides by mild acid hydrolysis and were isolated by paper chromatography. Both sets of 14C-oligosaccharides had similar mobilities suggesting that they were qualitatively similar, except that those formed in the presence of "acceptor" lipid had much more radioactivity. The individual oligosaccharides were purified on a calibrated column of Sephadex G-25 and were then subjected to various treatments to obtain information about their structures. The molecular weights of the larger oligosaccharides ranged from about L1210 to 1720 indicating they probably contained from 6 to 10 sugar residues. Strong acid hydrolysis of the oligosaccharide with a molecular weight of 1350, followed by reduction with NaB3H4, gave a ratio of [3H]hexitol to [3H]hexosaminitol that was compatible with the molecular weight (about 5:2). However, the hexitol fraction contained small amounts of [3H]glucitol in addition to [3H]mannitol. Thus, this oligosaccharide may contain small amounts of glucose in addition to mannose and GlcNAc. When the smaller oligosaccharides (i.e. those having 5 or 6 sugars) were treated with alpha-mannosidase, essentially of all the 14C was released as mannose, but only 30 to 50% of the radioactivity could be released from the larger oligosaccharides by this enzyme. Acetolysis of the oligosaccharide with a molecular weight of 1720 released the radioactivity as mannobiose and mannotriose suggesting that these oligosaccharides contain di- and trisaccharide branches linked to the main chain in 1 leads to 6 linkages.
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PMID:Biosynthesis of lipid-linked oligosaccharides in cotton fibers. Stimulation by lipids from pig liver. 84 36

The phosphoenolpyruvate sugar phosphotransferases of Staphylococcus aureus were surveyed biochemically to determine substrate range, inducibility and constitutivity, and requirements for soluble sugar-specific proteins. The substrate range is similar to that of the phosphotransferases of enteric bacteria, but the staphylococcal mannose and sorbitol systems are very inefficient. In addition, S. qureus has phosphotransferase activities for lactose and sucrose. The systems tested fell into two broad classes. Sugars for which there was substantial constitutive activity (fructose, mannose, sucrose, and glucose and its nonmetabolized analogues) did not require sugar-specific soluble factors for phosphorylation. Only in the case of fructose did growth in the presence of these constitutive sugars induce the corresponding phosphotransferase activity to higher levels. Kinetic experiments with each of these constitutive sugars yielded biphasic Hofstee plots; i.e., the kinetics were not characteristic of single enzymes. Preliminary experiments suggest that sucrose phosphorylation may involve the glucose and/or fructose systems. Truly inducible sugar phosphotransferase systems represent a second class; those for lactose and mannitol are the only members thus far identified. These systems are absent from uninduced cells, require soluble sugar-specific factors, and exhibit linear Hofstee plots. Sorbitol is apparently transported very poorly by intact cells but is an inducer of the mannitol system; it is phosphorylated efficiently in vitro by extracts of cells grown on either hexitol, but is taken up by intact cells at 0.1% of the mannitol rate.
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PMID:Initial characterization of hexose and hexitol phosphoenolpyruvate-dependent phosphotransferases of Staphylococcus aureus. 86 62

The effect of three monosaccharides, three disaccharides, two dipeptides, combinations of tryptophan with two hexoses, one hexitol, and two amino acids ongastric emptying was studied in dogs to further define the samll intestinal receptors responsive to osmolytes and tryptophan. On a molar basis the disacchardies and dipeptides were almost twice as potent as their respective constituent monosaccharides or amino acids implying that the osmoreceptor is deep to the brush border disaccharidases and cytosol dipeptidases. Tryptophan probably acts by a mechanism different from the osmoreceptor since slowing of gastric emptying by tryptophan was inhibited by methionine which has no effect on a stimulant of the osmoreceptor mechanism. Lysine unlike methionine does not share the neutral amino acid transport pathway with tryptophan. Lysine did not change the inhibitory effect of tryptophan on gastric emptying. This imples that transport of tryptophan into the intestinal cell is necessary for its slowing effect. Glucose and galactose also inhibited the tryptophan effect whereas a nonabsorbed hexitor, mannitol, was without effect. Interference by the hexoses was also probably by competition with tryptophan for transport into the cell. These studies further indicate that the tryptophan receptor is different from the osmoreceptor.
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PMID:Osmoltye and tryptophan receptors controlling gastric emptying in the dog. 97 Apr 66

A hexitol-inducible, phosphoenolpyruvate-dependent phosphotransferase system was demonstrated in Streptococcus mutans. Cell-free extracts obtained from mannitol-grown cells from a representative strain of each of the five S. mutans serotypes (AHT, BHT, C-67-1, 6715, and LM7) were capable of converting mannitol to mannitol-1-phosphate by a reaction which required phosphoenolpyruvate and Mg2+. Mannitol and sorbitol phosphotransferase activities were found in cell-free extracts prepared from cells grown on the respective substrate, but neither hexitol phosphotransferase activity was present in extracts obtained from cells grown on other substrates examined. A heat-stable, low-molecular-weight component was partially purified from glucose-grown cells and found to stimulate the mannitol phosphotransferase system. Divalent cations Mn2+ and Ca2+ partially replaced Mg2+, while Zn2+ was found to be highly inhibitory.
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PMID:Mannitol transport in Streptococcus mutans. 119 41

This report describes a method for the solubilization of micro-particulate (1-->3)-beta-D-glucan. Insoluble glucan is dissolved in methyl sulfoxide and urea (8 M) and partially sulfated at 100 degrees. The resulting water-soluble product is called glucan sulfate. The conversion rate is 98%, and the preparation is endotoxin free as determined by the Limulus lysate procedure. Glucan sulfate is composed of 34.06% C, 6.15% H, 50.30% O, 5.69% S and 3.23% N, and has a repeating unit empirical formula of (C6H10O5)8.3 SO3NH4+.4 H2O, suggesting that, on the average, a sulfate group is substituted on every third glucose subunit along the polymer. Molecular weight averages, polydispersity, and intrinsic viscosity were determined by aqueous high-performance size-exclusion chromatography (HPSEC). Two polymer peaks were resolved. Peak 1 (Mw = 1.25 x 10(6) g/mol) represents < 1% of the total polymer mass. Peak 2 (Mw = 1.45 x 10(4) g/mol) comprises > 99% of polymers. 13C NMR spectroscopy confirmed the beta-(1-->3) interchain linkage. In solution, glucan sulfate polymers self-associate in a triple helix. Glucan sulfate stimulates murine bone marrow proliferation following intravenous administration. The ability to prepare a immunologically active, water-soluble (1-->3)-beta-D-glucan preparation will greatly enhance the clinical utility of this class of compounds.
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PMID:Development of a water-soluble, sulfated (1-->3)-beta-D-glucan biological response modifier derived from Saccharomyces cerevisiae. 147 7

This report describes a method for the solubilization of a micro-particulate beta-D-glucan. Insoluble glucan is dissolved in methyl sulfoxide and urea (8M) and partially phosphorylated at 100 degrees. The resulting water-soluble product is called glucan phosphate. The conversion rate is 70%, and the preparation is endotoxin free as determined by the Limulus lysate procedure. Glucan phosphate is composed of 34.66% C, 6.29% H, 42.83% O, and 2.23% P and has a repeating-unit empirical formula of (C6H10O5)7.PO3H2, indicating a phosphate group substitution on every seventh glucose subunit. Molecular-weight averages, polydispersity, and intrinsic viscosity were determined by aqueous high-performance size-exclusion chromatography (s.e.c.) with on-line, multi-angle laser light scattering (m.a.l.l.s.) photometry and differential viscometry (d.v.). Two polymer peaks were resolved. Peak 1 (Mw = 3.57 x 10(6) daltons), represents approximately 2% of the total polymers, while peak 2 (Mw = 1.10 x 10(5) daltons) comprises approximately 98% of polymers. 13C- and 31P-n.m.r. spectroscopy confirmed the beta-1,3 interchain linkage and the presence of a phosphate group. In solution, glucan phosphate polymers self-associate in a triple-helical arrangement. The ability to prepare a immunologically active, non-toxic, water-soluble beta-D-glucan preparation will greatly enhance the clinical utility of this class of compounds.
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PMID:A method for the solubilization of a (1----3)-beta-D-glucan isolated from Saccharomyces cerevisiae. 180 35

The mass spectra of permethylated methyl 4,6-O-(1-carbomethoxyethylidene)-D-hexopyranoside and 1,5-anhydro-D-hexitol of glucose, galactose, and mannose and permethylated methyl 5,6-O-(1-carbomethoxyethylidene)-D-galactofuranoside and 1,4-anhydro-D-galactitol have been determined. The stability of each compound toward methanolysis and reductive cleavage is discussed. These techniques permit the identification of the acetalic linkages of pyruvic acid present in polysaccharides.
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PMID:Analysis of pyruvic acid acetal containing polysaccharides by methanolysis and reductive cleavage methods. 181 80


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