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

The temporal depletion and accumulation of polyols were investigated in the fungus Geotrichum cnadidum. The major intracellular polyols were tentatively identified by paper chromatography as mannitol and arabitol. Inositol was also present in small quantities, and trehalose was also detected in appreciable concentrations. Germination and vegetative growth depended on the type and concentration of the sole exogenous carbon source. Mannitol occurred in arthrospores at 9.4% of the dry weight after several days growth in 2% (w/v) glucose solid medium, and became depleted during germination and vegetative growth in liquid medium containing 2% (w/v) glucose, 2% (w/v) sodium acetate or 25% (w/v) glucose as sole carbon source. This hexitol latter accumulated during arthrosporulation. The depletion and accumulation of ethanol-soluble carbohydrate believed to be primarily trehalose was temporally similar to that of mannitol. Arabitol accumulated intracellularly during germination and vegetative growth in sodium acetate medium and 25% glucose medium. This pentitol was not detected intracellularly at any culture age during growth in 2% glucose medium. Prolonged incubation of the culture in 25% glucose medium after stationary phase was reached resulted in the gradual disappearance of arabitol from the arthrospores simultaneously with an increase in intracellular mannitol. In comparison, ethanol-soluble carbohydrate did not change with prolonged incubation in this medium.
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PMID:Temporal accumulation of mannitol and arabitol in Geotrichum candidum. 677 36

Vectorial transphosphorylation of hexitols, catalyzed by enzymes II of the bacterial phosphotransferase system, was studied in intact cells and membrane vesicles of Escherichia coli. In strains depleted of phosphoenolpyruvate and unable to metabolize the internal hexitol phosphate, internal mannitol-1-phosphate stimulated uptake of extracellular [14C]mannitol, whereas external mannitol stimulated release of [14C]mannitol from the intracellular [14C]mannitol-1-phosphate pool. The stoichiometry of mannitol uptake to mannitol release was 1:1. Glucitol did not promote release of [14C]mannitol from the mannitol phosphate pool but stimulated release of [14C]glucitol from internal glucitol phosphate pools when the glucitol enzyme II was induced to high levels. In E coli cells and membrane vesicles, both vectorial and nonvectorial transphosphorylation reactions of hexitols and hexoses were demonstrated. The nonvectorial reactions, but not the vectorial reactions, catalyzed by the mannitol and glucose enzymes II, were inhibited by p-chloromercuriphenyl sulfonate, a membrane-impermeable sulfhydryl reagent which inactivates enzymes II. Similarly, glucose-6-sulfate, an inhibitor of the glucose enzyme II-catalyzed transphosphorylation reaction, specifically inhibited the nonvectorial reaction. This compound was shown to be a noncompetitive inhibitor of methyl alpha-glucoside phosphorylation employing phospho-HPr as the phosphate donor. It apparently exerts its inhibitory effect by exclusive binding to the sugar phosphate binding site on the enzyme II complex. The results are consistent with the conclusion that enzymes II can exist in two distinct dispositions in the membrane, one of which catalyzes vectorial transphosphorylation, and the other catalyzes nonvectorial transphosphorylation.
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PMID:Vectorial and nonvectorial transphosphorylation catalyzed by enzymes II of the bacterial phosphotransferase system. 678 May 16

A polyclonal antibody specific for the Amadori compound, a product of an early stage of the Maillard reaction, was raised in rabbits by immunization with hexitol-lysine (1-glucitol-lysine or 1-mannitol-lysine) coupled with various carrier proteins. The affinity purified antibody has a high titre and preferentially recognizes the glucose adduct, in the presence of sodium borohydride, as judged on enzyme-linked immunosorbent assay as well as immunoblot analysis. The glycated proteins (Amadori products) in various tissues of normal and streptozotocin-induced diabetic rats were examined by immunoblot analysis. In diabetic conditions, kidney, liver, lens, brain and lung proteins are more susceptible to glycation than other tissue proteins. Heart, spleen, adrenal gland and muscle proteins exhibit similar extents of glycation in both normal and diabetic conditions. This is the first demonstration of a specific antibody against the Amadori compound being raised with a synthetic compound, and of the tissue distribution of glycated proteins in normal and diabetic conditions. The antibody was very useful for in vitro and in vivo experiments on the Maillard reaction.
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PMID:Immunological detection of glycated proteins in normal and streptozotocin-induced diabetic rats using anti hexitol-lysine IgG. 754 37

The interaction of in vitro short-term glycated rat serum albumin with rat peritoneal cells (40% macrophages) was investigated. Using 125I-labeled albumins the following results were obtained. Glycated albumins showed a binding reaction at 4 degrees C, which appeared to reach equilibrium within 2 h. The concentration-dependent binding of glycated albumin showed saturation. Binding data evaluated for glycated albumin using the Sips equation are: average association constant Ko = 3.15 x 10(7) M-1 with a heterogeneity index of a = 0.8 and 1.12 x 10(4) binding sites per cell. Such binding sites were identified in 40% of the peritoneal cell preparations studied. Native albumins, maleylated albumin, chondroitinsulfates, polylysine, lysine, fructose, glucose and hexitol-lysine could not compete with radio-labeled glycated rat albumin for its binding site on peritoneal cells. Effective competitors were glycated human serum albumin, glycated polylysine and fructose-lysine. Although the contamination with minute amounts of advanced glycosylation end products (AGE) could not be excluded, short-term glycated albumin was found to be bound to membranes of peritoneal phagocytotic cells by fructose-lysine specific proteins, whose approximately defined molecular masses of 290 kDa are distinct from hitherto described binding proteins for AGE- and aldehyde-modified proteins or for the scavenger receptors.
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PMID:Binding sites for short-term glycated albumin on peritoneal cells of the rat. 848 65

Cryptococcus neoformans produces large amounts of the acyclic hexitol mannitol in culture and infected animals, but the functional and pathogenic significance of mannitol production by this fungus is not known. We exposed C. neoformans H99 (Cn H99) to UV irradiation (1 x LD50) and screened survivors for mannitol production. A mutant, Cn MLP (Mannitol Low Producer), synthesized less mannitol from glucose (2.7 vs 8.2 nmol per 10(8) cells min-1 at 37 degrees C) and contained less intracellular mannitol (1 vs 11 mumol per 10(6) cells at 37 degrees C) than did Cn H99. Cn MLP and Cn H99 were similar with respect to carbon assimilation patterns, rates of glucose consumption, growth rates at 30 degrees C, urease and phenoloxidase activities, morphology, capsule formation, mating type, electrophoretic karyotype, rapid amplification of polymorphic DNA (RAPD) patterns and antifungal susceptibility. However, Cn MLP was more susceptible than was Cn H99 to growth inhibition and killing by heat and high NaCl concentrations. Also, the LD50 values in mice injected intravenously were 3.7 x 10(6) c.f.u. for Cn MLP compared to 6.9 x 10(2) c.f.u. for Cn H99. Moreover, 500 c.f.u. Cn H99 intravenously killed 12 of 12 mice by 60 d, whereas all mice given the same inoculum of Cn MLP survived. Classical genetic studies were undertaken to determine if these differences were due to a single mutation, but the basidiospores were nonviable. These results suggest that the abilities of C. neoformans to produce and accumulate mannitol may influence its tolerance to heat and osmotic stresses and its pathogenicity in mice.
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PMID:Stress tolerance and pathogenic potential of a mannitol mutant of Cryptococcus neoformans. 893 20

Glucosamine-6-phosphate synthase (GlcNP-synthase) catalyzes the formation of glucosamine 6-phosphate from fructose 6-phosphate using the gamma-amide functionality of glutamine as the nitrogen source. In the absence of glutamine, GlcNP-synthase was recently found to catalyze the formation of glucose 6-phosphate corresponding to a phosphoglucoisomerase-like activity. Here we report active-site directed, irreversible inhibition of Escherichia coli GlcNP-synthase (k(inact) = 0.60 +/- 0.05 min(-1), Kirr = 1.40 +/- 0.20 mM) by anhydro-1,2-hexitol 6-phosphates previously known as irreversible inhibitors of phosphoglucoisomerase. Enzyme inactivation with the tritiated affinity label, followed by tryptic digestion and purification of the radioactive fragments, allowed identification of three peptides. Two of them, accounting for 54% of the recovered radioactivity, are believed to result from the nucleophilic attack of side-chain carboxylates of Glu255 and Glu258 and thiol of Cys300 of the fructose-6-phosphate-binding site on the epoxide functionality of the inhibitor. The major peptide corresponds to derivatization of the N-terminal cysteine from the glutamine-binding site by the inhibitor. These results provide evidence for the close proximity of glutamine and fructose-6-phosphate-binding sites recently suggested by Bearne [Bearne, S. L. (1996) J. Biol. Chem. 271, 3052-3057].
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PMID:Affinity labeling of Escherichia coli glucosamine-6-phosphate synthase with a fructose 6-phosphate analog--evidence for proximity between the N-terminal cysteine and the fructose-6-phosphate-binding site. 915 73

Amyotrophic lateral sclerosis (ALS) involves the progressive degeneration of motor neurons in the spinal cord and motor cortex. It has been shown that 15-20% of patients with familial ALS (FALS) have defects in the Sod1 gene that encodes Cu, Zn-superoxide dismutase (SOD). To elucidate the pathological role of mutated Cu, Zn-SODs in FALS, the susceptibility of mutants to glycation was examined. Mutated Cu, Zn-SODs (G37R, G93A, and I113T) related to FALS and wild type were produced in a baculovirus/insect cell expression system. Glycated and nonglycated proteins were separated on a boronate column, and the nonglycated fraction was then incubated with glucose. The mutated Cu, Zn-SODs were found to be highly susceptible to glycation compared with the wild-type enzyme as estimated by Western blot analysis using an anti-hexitol lysine antibody. The mutated Cu, Zn-SOD incubated with glucose generated higher levels of hydrogen peroxide than the wild-type enzyme. Mutated Cu, Zn-SODs were also shown to be highly susceptible to fructation, and the fructated mutant also produced higher levels of hydrogen peroxide than the wild type. These results suggest that high susceptibility of mutated Cu, Zn-SODs to glycation could be the origin of the oxidative stress associated with neuronal dysfunction in FALS.
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PMID:Glycation proceeds faster in mutated Cu, Zn-superoxide dismutases related to familial amyotrophic lateral sclerosis. 1262 32

Mannitol is a sugar polyol claimed to have health-promoting properties. A mannitol-producing strain of Lactococcus lactis was obtained by disruption of two genes of the phosphoenolpyruvate (PEP)-mannitol phosphotransferase system (PTS(Mtl)). Genes mtlA and mtlF were independently deleted by double-crossover recombination in strain L. lactis FI9630 (a food-grade lactate dehydrogenase-deficient strain derived from MG1363), yielding two mutant (Delta ldh Delta mtlA and Delta ldh Delta mtlF) strains. The new strains, FI10091 and FI10089, respectively, do not possess any selection marker and are suitable for use in the food industry. The metabolism of glucose in nongrowing cell suspensions of the mutant strains was characterized by in vivo (13)C-nuclear magnetic resonance. The intermediate metabolite, mannitol-1-phosphate, accumulated intracellularly to high levels (up to 76 mM). Mannitol was a major end product, one-third of glucose being converted to this hexitol. The double mutants, in contrast to the parent strain, were unable to utilize mannitol even after glucose depletion, showing that mannitol was taken up exclusively by PEP-PTS(Mtl). Disruption of this system completely blocked mannitol transport in L. lactis, as intended. In addition to mannitol, approximately equimolar amounts of ethanol, 2,3-butanediol, and lactate were produced. A mixed-acid fermentation (formate, ethanol, and acetate) was also observed during growth under controlled conditions of pH and temperature, but mannitol production was low. The reasons for the alteration in the pattern of end products under nongrowing and growing conditions are discussed, and strategies to improve mannitol production during growth are proposed.
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PMID:Engineering Lactococcus lactis for production of mannitol: high yields from food-grade strains deficient in lactate dehydrogenase and the mannitol transport system. 1500 67

Recently, we demonstrated that the control of cytosolic and mitochondrial redox balance and the cellular defense against oxidative damage is one of the primary functions of NADP(+)-dependent isocitrate dehydrogenase (ICDH), because it supplies NADPH for antioxidant systems. When exposed to reducing sugars such as glucose, glucose 6-phosphate, and fructose, ICDH was susceptible to oxidative modification and damage, which was indicated by a loss of activity and fragmentation of the peptide as well as by the formation of carbonyl groups. The glycated ICDH was isolated and identified by boronate-affinity chromatography and immunoblotting with anti-hexitol-lysine antibody. The active site lysine residue, Lys(212), was identified as one of the major sites of nonenzymatic glycation of ICDH. The structural alterations of modified enzymes were indicated by changes in thermal stability, intrinsic tryptophan fluorescence, and binding of the hydrophobic probe 8-anilino-1-naphthalene sulfonic acid. When we examined the antioxidant role of mitochondrial ICDH against glycation-induced cytotoxicity with HEK293 cells transfected with the cDNA for mouse mitochondrial ICDH in sense and antisense orientations, a clear inverse relationship was observed between the amount of mitochondrial ICDH expressed in target cells and their susceptibility to glycation-mediated cytotoxicity. Mitochondrial ICDH was purified by immunoprecipitation and probed with anti-hexitol-lysine antibody, which revealed increased levels of glycated ICDH in the kidneys of diabetic rats and in the lenses of diabetic patients suffering from cataracts. A decrease in ICDH activity was observed in those tissues. We also found that levels of glycated ICDH increased in IMR-90 cells and rat kidney during normal aging. The glycation-mediated damage to ICDH may result in the perturbation of cellular antioxidant defense mechanisms and subsequently lead to a pro-oxidant condition and may contribute to various pathologies associated with the general aging process and long-term complications of diabetes.
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PMID:Glycation-induced inactivation of NADP(+)-dependent isocitrate dehydrogenase: implications for diabetes and aging. 1552 36

Five diastereomeric trideoxy-1,6-iminohexitols were synthesised, and their inhibitory activities were determined against selected glycosidases. For comparison, 1,4,5-trideoxy-1,5-imino-D-lyxo-hexitol, the 4-deoxy derivative of 1-deoxymannojirimicin, was prepared by enzymatic isomerisation of 6-azido-3,6-dideoxy-D-ribo-hexose into the corresponding 2-ulose and subsequent hydrogenation accompanied by intramolecular reductive amination.
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PMID:Syntheses of sugar-related trihydroxyazepanes from simple carbohydrates and their activities as reversible glycosidase inhibitors. 1600 3


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