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PubMed1999

Measurement of monosaccharides and conversion of glucose to acetate in anoxic rice field soil

Degradation of glucose has been implicated in acetate production in rice field soil, but the abundance of glucose, the temporal change of glucose turnover, and the relationship between glucose and acetate catabolism are not well understood. We therefore measured the pool sizes of glucose and acetate in rice field soil and investigated the turnover of [U-14C]glucose and [2-14C]acetate. Acetate accumulated up to about 2 mM during days 5 to 10 after flooding of the soil. Subsequently, methanogenesis started and the acetate concentration decreased to about 100 to 200 &mgr;M. Glucose always made up >50% of the total monosaccharides detected. Glucose concentrations decreased during the first 10 days from 90 &mgr;M initially to about 3 &mgr;M after 40 days of incubation. With the exception at day 0 when glucose consumption was slow, the glucose turnover time was in the range of minutes, while the acetate turnover time was in the range of hours. Anaerobic degradation of [U-14C]glucose released [14C]acetate and 14CO2 as the main products, with [14C]acetate being released faster than 14CO2. The products of [2-14C]acetate metabolism, on the other hand, were 14CO2 during the reduction phase of soil incubation (days 0 to 15) and 14CH4 during the methanogenic phase (after day 15). Except during the accumulation period of acetate (days 5 to 10), approximately 50 to 80% of the acetate consumed was produced from glucose catabolism. However, during the accumulation period of acetate, the rate of acetate production from glucose greatly exceeded that of acetate consumption. Under steady-state conditions, up to 67% of the CH4 was produced from acetate, of which up to 56% was produced from glucose degradation.

Journal Article↗
PubMed1973

Facilitated diffusion of monosaccharides in Saccharomyces cerevisiae: experimental investigation of kinetic parameters without the assumptions of symmetry.

Until the question of symmetry or asymmetry in the facilitated diffusion of monosaccharides by Saccharomyces cerevisiae is resolved, attempts to study the transport process cannot be based on assumptions of symmetry, such as equal concentrations at equilibrium or kinetic parameters that are equal in opposite directions. The assumptions of symmetry may be circumvented by measuring efflux against water and against various external concentrations of sugar. The measurement of efflux against water eliminates any involvement of influx, and the separate determinations of influx and efflux parameters do not require that the parameters be equal. Furthermore, the use of relative internal concentrations eliminates any necessity of assuming that the equilibrium concentrations are equal. Since the influx and efflux parameters are to be compared, the measurement of influx on effluxing cells allows both sets of parameters to be determined on cells which are physiologically the same. This procedure has been tested by obtaining the kinetic parameters of l-sorbose transport. The validity of these parameters was demonstrated by using them to generate theoretical efflux curves that fit the experimental data and by showing that they give the best fit curve to the relationship of velocity and permeant concentration. Although the question of symmetry remains unanswered, this procedure has opened the way for experimental evaluation of the situation and further investigation of the transport process in yeast.

Biological Transport↗
PubMed1968

Phosphate dependence of monosaccharide transport in Nocardia.

Uptake of the monosaccharides d-glucose and d-mannose by Nocardia asteroides and N. brasiliensis is dependent on the presence of an adequate phosphate concentration in the environment. When phosphate is replaced by solutions of sodium chloride or potassium chloride of identical ionic strength, there is no sugar uptake. In the presence of iso-osmolar concentrations of sodium arsenate, there is, however, sugar uptake activation. When nonmetabolizable 3-O-methyl d-glucose is used, most of the sugar taken up can be shown to be in the cell at a concentration never exceeding that of the external medium. Phosphate, or arsenate, seems to be essential for the actual migration of the sugar through the cell envelope. The transport of the nonmetabolizable 3-O-methyl glucose also requires phosphate, and the transport seems to be of a type that does not require energy.

Arsenic↗
PubMed1983

Monosaccharide transport and hexokinase activity in leg muscles from cardiomyopathic hamsters.

The facilitated diffusion system for monosaccharides was studied with nonmetabolized 3-O-methyl-D-glucose (3-O-MG) and hexokinase activity was determined with 2-deoxyglucose (2-DG) in extensor digitorum longus (EDL) and soleus muscles from BIO 14.6 (dystrophic) hamsters. Motor activity was recorded at 2 months of age. F1B (normal) hamsters were controls. In EDL (fast-twitch) muscle, sugar transport was unaltered at 6 weeks; at 2 to 5 months the normal decrease in sugar transport with time was reduced, decreasing stimulation of the facilitated diffusion system by anoxia. Phosphorylation in EDL muscles, measured at 2 months, probably was decreased. In soleus (slow-twitch) muscle, 3-O-MG transport was unaltered with age but hexokinase activity, determined at 2 months, was greatly increased in the quiescent state and during stimulation at 2 Hz. Motor activity was less, but not significantly, in the dystrophic hamsters. The results indicate that the alterations in glucose metabolism depend upon both muscle type and age. We interpret the changes in dystrophic fast- and slow-twitch muscles as reflecting compensatory mechanisms to increase the generation of energy.

3-O-Methylglucose↗
PubMed1993

Binding of lysozyme to synthetic monosaccharide lipid A analogue, GLA60.

Recent studies by our group suggested that lysozyme (LZM) has a high affinity for bacterial lipopolysaccharide (LPS) of both the smooth and rough forms, and inhibits various immunomodulatory activities of LPS. GLA60 is a synthetic monosaccharide analogue of bacterial lipid A, well-known as sharing large part of lipid A activities but with very low toxicity. In this study, we characterized the interaction of LZM with GLA60 in comparison to that with E. coli 0111 LPS (smooth form), taking a physicochemical approach. Using a dansylated lysozyme probe (DNS-LZM), LZM was found to bind to GLA60 in all 3 of its forms, free acid, triethylamine (TEA) salt and bovine serum albumin (BSA) complex of GLA60, as well as natural LPS. Compared with LPS, the complex formation of the TEA salt was weakly dependent on temperature and incubation time. LZM also bound to biologically inactive GLA analogues, GLA 64 and GLA69, at a high affinity, as well as to GLA 60. By using chemically modified LZM, it was found that the ionic as well as hydrophobic interactions are important for the complex formation.

Chemical Phenomena↗
PubMedDate not supplied

Monosaccharides and disaccharides decrease the Km for phosphorylation of a membrane-bound enzyme ATPase.

The disaccharides trehalose and sucrose, and to a lesser extent the monosaccharides glucose and fructose, decrease the apparent Km of the Ca2+, Mg(2+)-ATPase of sarcoplasmic reticulum for Pi. This effect is more pronounced at pH 7.4 than at pH 6.2. The enzyme is not phosphorylated by Pi when the temperature of the medium is decreased to 0 degree C, but when 1.5 M trehalose or sucrose is present phosphoenzyme formation increases to 0.5 mumol E-P/g protein.

Animals↗
PubMed1986

Synthesis of three 3-C-hydroxymethylpentoses with the D-ribo-, D-xylo- and L-lyxo-configurations. Identification of the latter with a monosaccharide isolated from phase I Coxiella burnetii lipopolysaccharide.

Three 3-C-hydroxymethylpentoses with the D-ribo-, D-xylo and L-lyxo-configurations, were synthesised via nitromethane addition for the first two and 1,3-dithiane addition for the last one, to appropriate 3-ulose derivatives. 3-C-Hydroxy-methyl-L-lyxose is identical with a monosaccharide component previously isolated from hydrolysates of the phase I Coxiella burnetii lipopolysaccharide.

Chromatography, Gas↗
PubMed1987

The production of tumor necrosis factor by mouse bone marrow-derived macrophages in response to bacterial lipopolysaccharide and a chemically synthesized monosaccharide precursor.

Lipid X, a monosaccharide biosynthetic precursor of lipid A, has been chemically synthesized and was shown to induce bone marrow-derived macrophages to release tumor necrosis factor (TNF) in vitro. However, relatively high amounts of lipid X were necessary for induction, and the levels of TNF were much less than those induced by small amounts of lipid A itself or LPS. Lipid X prepared by extraction of Escherichia coli mutants induced higher levels of TNF than the chemically synthesized material, but this is probably partially due to amounts of impurities in the extracted material. Pretreatment of macrophages with IFN-gamma resulted in the release of higher amounts of TNF on subsequent induction with either LPS or lipid X. In contrast, pretreatment of macrophages with LPS induced hyporesponsiveness for TNF production on subsequent rechallenge with LPS. Lipid X, on the other hand, was incapable of making macrophages hyporesponsive for TNF production.

Animals↗
PubMed1983

Suppression of T cell cytotoxicity by nude mouse spleen cells: reversal by monosaccharides and interleukin 2.

The effects of monosaccharides on the suppression of cytotoxic T cell generation by spleen cells from nu/nu mice were examined. Suppression of the B6 anti-BALB/c response and the B6 anti-C3H response was reversed by alpha-methyl-D-galactoside (alpha MG) but not other sugars, including beta MG. Suppression was associated with a decrease in the level of IL 2, which suggests competition; this decrease was also reversed by alpha MG.

Animals↗
PubMed1984

The biosynthesis of gram-negative endotoxin. Formation of lipid A disaccharides from monosaccharide precursors in extracts of Escherichia coli.

We have discovered an enzyme in the cytosol of Escherichia coli that generates lipid A disaccharides from monosaccharide precursors by the following route: 2,3-diacyl-GlcN-1-P + UDP-2,3-diacyl-GlcN---- 2,3-diacyl-GlcN (beta, 1----6) 2,3-diacyl-GlcN-1-P + UDP. Previous studies from our laboratory have documented the presence in vivo of the precursors 2,3-diacylglucosamine 1-phosphate (2,3-diacyl-GlcN-1-P) (lipid X of E. coli) and UDP-2,3-diacylglucosamine (UDP-2,3-diacyl-GlcN) (Bulawa, C.E., and Raetz, C.R.H.J. Biol. Chem. 259, 4846-4851). Both substrates are novel glucosamine-derived phospholipids, acylated with beta-hydroxymyristoyl moieties, and they accumulate in E. coli mutants defective in the pgsB gene. Synthetic ADP-, GDP-, and CDP-2,3-diacylglucosamines are inefficient substrates compared to the naturally occurring UDP derivative. The free-acid form of the tetraacyldisaccharide 1-phosphate product (C68H129N2O20P) that is generated in vitro has Mr = 1325.74 as judged by fast atom bombardment mass spectrometry. Mild acid hydrolysis (0.1 M HCl for 30 min at 100 degrees C) liberates greater than 95% of the phosphate moiety as Pi. Detailed analysis by 1H and 13C NMR spectroscopy confirms the presence of a phosphate residue at position 1 of the disaccharide, an alpha-anomeric configuration at the reducing end, and a beta, 1----6 linkage between the two glucosamines. Importantly the disaccharide 1-phosphate synthase is missing in extracts of E. coli strains harboring the pgsB1 mutation, consistent with the massive accumulation of 2,3-diacyl-GlcN-1-P and UDP-2,3-diacyl-GlcN in vivo. The enzymatic reaction reported here represents a major biosynthetic route for the formation of lipid A disaccharides in E. coli and other Gram-negative bacteria. An in vitro system for the biosynthesis of lipid A disaccharides has not been described previously.

Disaccharides↗
PubMedDate not supplied

Monosaccharide transport across membranes of human spermatozoa. II. Basic properties of D-fructose and D-glucose uptake.

D-glucose uptake by human spermatozoa shows like D-fructose uptake a hyperbolic kinetic. The affinities to the transport system are similar, but the maximal capacity of D-glucose transport is greater than the D-fructose transport. Both transport processes are inhibited by monoiodoacetate. Therefore these transports can be regarded as carrier-mediated active transports. The D-glucose transport moreover is inhibitable by ouabain and is influenced by extracellular Na+. These differences could be the expression that for both monosaccharides different transport systems exist. But the dependence of D-glucose and D-fructose uptake on the extracellular D-fructose-D-glucose-relation permits the conclusion that both systems interact with another.

Biological Transport, Active↗
PubMed1980

Synthesis of monosaccharide nitrosamines.

This paper describes the chemical synthesis of a chain-branched, monosaccharide nitrosamine: 3-[N-nitroso-N-ethyl]-aminomethyl-D-allose. Nitrosamines with alpha-carbon-carbon-bonded carbohydrate residues (hydrophilic carrier) could be interesting for experimental cancer research; specifically, in biological experiments (testing for carcinogenic, mutagenic or teratogenic effects), biochemical experiments (enzymatic activation, metabolites) and physiological experiments (resorption studies).

Hexoses↗
PubMed1980

Transport of monosaccharides by the small intestine of genetically diabetic mice.

Small intestinal absorptive function was investigated in genetically diabetic mouse model (C57 BL/KSJ dbm) in order to determine the long-term effects of genetic and uncontrolled diabetes mellitus on intestinal function. Initial rates of uptake of nonmetabolizable glucose analogs, beta-methyl-D-glucoside and 3-O-methyl-D-glucose were determined in diabetic mice and their littermate controls using everted sacs from proximal and distal halves of the intestine. In addition, intestinal weight, intestinal length, mucosal protein, and DNA were measured. There were no significant differences between controls and diabetics in rates of uptake by either proximal or distal segments. Kinetic characteristics of uptake, Km and Vmax, were similar in controls and diabetics. These results clearly demonstrate that intestinal transport of monosaccharides is not altered in genetic diabetes, and therefore are in contrast to augmented transport reported in the early phase of drug-induced diabetes but similar to the results observed in chronic drug-induced diabetes. However, diabetic mice exhibited stimulated intestinal growth similar to rats with chronic drug-induced diabetes.

Animals↗
PubMed2000

Decreased monosaccharide transport in renal brush-border membrane vesicles of spontaneously hypertensive rats.

Na(+)-dependent D-glucose and D-galactose transport were studied in brush-border membrane vesicles (BBMVs) from kidney cortex isolated from both spontaneously hypertensive rats (SHR) and their normotensive genetic control Wistar-Kyoto (WKY) rats. Initial rates and accumulation ratios of Na(+)-dependent D-glucose and D-galactose transport were significantly lower in SHR compared with WKY, the observed decreases being similar for both substrates. To explain the reduction in sugar transport by renal BBMVs, the density of Na(+)-dependent sugar cotransporters was studied in BBMVs from kidney cortex isolated from SHR and WKY rats. Phlorizin-specific binding and Western blot analysis indicated a reduction in the density of the cotransporters in SHR relative to WKY rats. This reduction was similar to those found for the initial rates and accumulation ratios for D-glucose and D-galactose in SHR. Na+ uptake, studied using 22Na+, was significantly increased in SHR, so the observed reduction in sugar transport could be due to disruption of the Na+ gradient between renal BBMVs in SHR. Furthermore, a significant decrease in the activity of Na(+)-K(+)-ATPase was observed in SHR. In conclusion, changes in the density of the Na(+)-dependent sugar cotransporter and in the Na+ gradient across the brush-border membranes might be involved in the observed reduction in sugar transport by renal BBMVs from SHR.

Animals↗
PubMed1984

Specificity of the rat hepatocyte monosaccharide transporter.

The effect of a number of hexoses and pentoses on 3-O-methyl-D-glucose transport into isolated hepatocytes is reported. The hexoses tested inhibited transport in a competitive manner, with Ki values ranging from 80 to 190 mM. No significant inhibition was seen with either D-ribose or D-arabinose.

3-O-Methylglucose↗