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At least 325 records · Page 18Linked to original sources
PubMed2003

Crystal structure of Pseudomonas fluorescens mannitol 2-dehydrogenase: evidence for a very divergent long-chain dehydrogenase family.

Mannitol 2-dehydrogenase from Pseudomonas fluorescens (pfMDH) is a secondary alcohol dehydrogenase that catalyzes the reversible NAD(P)-dependent oxidation of D-mannitol to D-fructose, D-arabinitol to D-xylulose, and D-sorbitol to L-sorbose. It is a member of the mostly prokaryotic family of long-chain mannitol dehydrogenases that so far includes 66 members. Unlike other alcohol and polyol dehydrogenases that utilize metal cofactors or a conserved active-site tyrosine for catalysis, an invariant lysine is the general base. The crystal structure of pfMDH in a binary complex with NAD(H) and a ternary complex with NAD(H) and D-mannitol have been determined to 1.7 and 1.8 A resolution respectively. Comparison of secondary structure assignment to sequence alignments suggest the shortest members of this family, mannitol-1-phosphate 5-dehydrogenases, retain core elements but lack secondary structural components found on the surface of pfMDH. The elements predicted to be absent are distributed throughout the primary sequence, implying that a simple truncation or fusion did not occur. The closest structural neighbors are 6-phosphogluconate dehydrogenase, UDP-glucose dehydrogenase, N-(1-D-carboxyethyl)-L-norvaline dehydrogenase, and glycerol-3-phosphate dehydrogenase. Although sequence identity is only a barely recognizable 7-10%, conservation of secondary structural elements as well as homologous residues that are contributed to the active site indicates they may be related by divergent evolution.

Crystallography, X-Ray↗
PubMed2003

Quantitation and test of enantiomeric purity of the L-ketohexoses by liquid chromatography with dual refractive index and laser-based chiroptical detection.

Experimental data for the synthetic methods of preparation of the L-ketohexoses have been lacking an analytical method for monitoring the chemical or enzymatic reactions described. Dual refractive index and laser-based chiroptical detection provides an ideal method for following the reactions, since the refractive index detector quantifies the amount of analyte, while the ratio of optical rotation to refractive index response allows the enantiomer mole fraction to be determined. Sulfonated polystyrenedivinylbenzene resin in the Ca form as the stationary phase with H2O at 80 degrees C as the eluent gives base-line separation of sorbose, fructose, tagatose, and psicose. Dependent on the complexity of the reaction mixture, analysis times range from 20 to 60 min.

Calibration↗
PubMed2002

The control of the proventriculus in the honeybee (Apis mellifera carnica L.) II. Feedback mechanisms.

The mechanisms underlying the control of solution transport rates through the proventriculus in foraging honeybees were investigated in individuals trained to collect defined amounts of sugar solutions. Following feeding, bees were injected either with metabolisable (glucose, fructose, trehalose), or non-metabolisable (sorbose) sugars, in order to distinguish between haemolymph osmolarity and haemolymph sugar levels as factors controlling the solution transport rates through the proventriculus. After a fixed period, workers were dissected in order to measure crop content and haemolymph sugar titers. Between feeding and dissection, the metabolic rate of every investigated forager was measured using open-flow respirometry. Bees injected with metabolisable sugars 15 min after feeding were observed to reduce their solution transport rates through the proventriculus, but injection of non-metabolisable sugars had no influence on them. This suggests that the solution transport rate through the proventriculus is controlled by the concentration of metabolisable compounds in the haemolymph, and not by the haemolymph osmolarity. A period of 10 min after injection of metabolisable sugars was enough to observe reduced solution transport rates. However, if bees were injected only 5 min after feeding, no reduced solution transport rates were observed 10 min after injection.

Journal Article↗
PubMed1977

Survey of some Fusarium moniliforme strains from different host plants for compounds possessing gibberellin-like activity.

Fifty cultures of Fusarium moniliforme were isolated from different hosts and were studied morphologically and physiologically for gibberellin production. Gibberellin production is not limited to rice isolates, since isolates from other host plants revealed also production. These isolates were highly utilizing sucrose, fructose, glucose, sorbose, maltose, mannose, xylose, and arabinose, more than lactose; also ammonium nitrate, ammonium sulphate, and ammonium tartrate were better utilized as nitrogen source than soybean, dry yeast, and corn steep liquor.

Aziridines↗
PubMed1997

Hemagglutinins in Anopheles quadrimaculatus, strains susceptible and refractory to Brugia malayi, and their role in the immune response to filarial parasites.

Hemagglutinins in the salivary gland extract and in the body fluid from strains of the mosquito, Anopheles quadrimaculatus, susceptible and refractory to the filarial parasite, Brugia malayi, had higher titers against Human A+, B- and O+, and sheep erythrocytes than against rabbit and jird erythrocytes. Hemagglutination activity in the body fluid was low in newly emerged females but increased and stabilized as they became older. Hemagglutination activity of the body fluid was not reduced by freezing at -20 degrees C, but it was destroyed following heating the body fluid to 60 degrees C and 100 degrees C for 45 min, indicating that the hemagglutinins are heat labile, and they are proteins or glycoproteins. Hemagglutinins in the salivary glands exhibited specificities for a broader range of carbohydrate moieties on the surface of Human A+ and sheep erythrocytes than those in the body fluid. Injections of specific carbohydrates in saline solution into B. malayi-infected females of the refractory strain of An. quadrimaculatus 24 hr after the infective blood meal showed that galactose, N-acetyl-D-galacto-samine, sorbose and mannose inhibited the increase in encapsulation (melanization) of L1 of B. malayi in the thoracic muscles of An. quadrimaculatus females when compared to those females injected with saline and other carbohydrates. The results suggest that hemagglutinins are present in the salivary gland extract and the body fluid of both strains of An. quadrimaculatus females and they may be involved in the immune response (encapsulation) to filarial parasites in An. quadrimaculatus.

Animals↗
PubMed2003

Membrane-derived oligosaccharides (MDOs) are essential for sodium dodecyl sulfate resistance in Escherichia coli.

We studied the role of membrane-derived oligosaccharides (MDOs) in sodium dodecyl sulfate (SDS) resistance by Escherichia coli. MDOs are also known as osmoregulated periplasmic glucans. Wild-type E. coli MC4100 grew in the presence of 10% SDS whereas isogenic mdoA and mdoB mutants could not grow above 0.5% SDS. Similarly, E. coli DF214, a mutant (pgi, zwf) unable to grow on glucose, exhibited conditional sensitivity to SDS in that it grew in gluconate and glucose or galactose but not in gluconate and mannose or sorbose. DF214 requires both gluconate and glucose/galactose because the gluconate is used for energy production, while glucose/galactose is used for MDO synthesis. Finally, the fate of E. coli cells subjected to SDS shock either during growth or when used as an inoculum is dependent on the presence or absence of sufficient MDOs. In both cases, cells grown under high-osmolarity (low-MDO) conditions were rapidly lysed by 5% SDS. Based on findings from a wild-type E. coli (MC4100), two mdo mutants and strain DF214 we conclude that MDOs are required for SDS resistance.

Cations↗
PubMed2004

Cloning, sequencing and functional analysis of Magnaporthe grisea MVP1 gene, a hex-1 homolog encoding a putative 'woronin body' protein.

A hex-1 homolog named MVP1 was isolated from an appressoria cDNA library of the rice blast fungus Magnaporthe grisea. The transcript of approximately 1.6 kb contains 546 bp of coding sequence with a 3' untranslated region about 168 bp long and a 5' untranslated region about 870 bp long. Southern gel blot analysis of genomic DNA following digestion with three restriction enzymes (BamHI, EcoRI, HindIII) indicated that the gene exists as a single copy in M. grisea genome. RNA gel blot analyses showed that MVP1 was highly expressed in germinating conidia and the mycelial stage compared to appressoria or non-germinated conidia. MVP1 showed a high degree of homology to the hex-1 gene recently described to encode a major protein in the woronin bodies of Neurospora crassa. Double homologous recombination was used to replace MVP1 with the hyg(R) gene. MVP1 knockout mutants showed apical swellings when grown on agar plates containing 2% sorbose but they were not impaired in any other vegetative or pathogenic properties evaluated. The pathological and other phenotypic consequences of gene disruption are discussed.

Cloning, Molecular↗
PubMed1997

Fructose and tagatose protect against oxidative cell injury by iron chelation.

To further investigate the mechanism by which fructose affords protection against oxidative cell injury, cultured rat hepatocytes were exposed to cocaine (300 microM) or nitrofurantoin (400 microM). Both drugs elicited massively increased lactate dehydrogenase release. The addition of the ketohexoses D-fructose (metabolized via glycolysis) or D-tagatose (poor glycolytic substrate) significantly attenuated cocaine- and nitrofurantoin-induced cell injury, although both fructose and tagatose caused a rapid depletion of ATP and compromised the cellular energy charge. Furthermore, fructose, tagatose, and sorbose all inhibited in a concentration-dependent manner (0-16 mM) luminolenhanced chemiluminescence (CL) in cell homogenates, indicating that these compounds inhibit the iron-dependent reactive oxygen species (ROS)-mediated peroxidation of luminol. Indeed, both Fe2+ and Fe3+ further increased cocaine-stimulated CL, which was markedly quenched following addition of the ketohexoses. The iron-independent formation of superoxide anion radicals (acetylated cytochrome c reduction) induced by the prooxidant drugs remained unaffected by fructose or tagatose. The iron-chelator deferoxamine similarly protected against prooxidant-induced cell injury. In contrast, the nonchelating aldohexoses D-glucose and D-galactose did not inhibit luminol CL nor did they protect against oxidative cell injury. These data indicate that ketohexoses can effectively protect against prooxidant-induced cell injury, independent of their glycolytic metabolism, by suppressing the iron-catalyzed formation of ROS.

Adenosine Triphosphate↗
PubMed1994

Differentiation of selected members of the family Neisseriaceae (Alysiella, Eikenella, Kingella, Simonsiella and CDC groups EF-4 and M-5) by carbohydrate fingerprints and selected phenotypic features.

On the basis of nucleic acid relationships, the family Neisseriaceae consists of the genera Neisseria, Kingella, Simonsiella and of Alysiella filiformis, Eikenella corrodens, and the CDC groups EF-4 and M-5. Differentiation, especially of the new members of the family, by conventional phenotypic characteristics is difficult and in some cases leads to doubtful results. On the other hand, cellular components proved to be suitable for the characterization of bacterial taxa. We investigated the cellular carbohydrates derived from whole cell hydrolysates of the above mentioned taxa with the exception of Neisseria by gas chromatography/mass-spectrometry. The analysis revealed characteristic patterns for all taxa considered, although with some species of which only few strains were investigated so far only preliminary results could be established. With the method used, the carbohydrate analysis could be completed within six hours starting from a pure culture. All strains investigated exhibited a common pattern with ribose, arabinose, glucose, and galactose. Qualitative and quantitative differences in contents of fucose, sorbose, rhamnose, threose, heptose, galactosamine and an amino sugar similar to glucosamine discriminated members of the taxa investigated. To achieve a taxonomically precise differentiation of the species investigated by conventional phenotypic features as available in commercial rapid test kits, these tests should be completed by the carbohydrate analysis technique presented.

Carbohydrates↗
PubMed2000

Ultrasound in organic electrosynthesis.

Mechanical effects induced by ultrasonication can be very helpful for the activation of electrochemical reactions. The continuous cleaning of the electrodes by ultrasound irradiation of the electrochemical cell or the enhancement of mass transfer at the electrodes are examples of such activation. Finally, ultrasonication can play an important part for the orientation of reactions whose selectivities are very sensitive to stirring. Two very different examples have been chosen to illustrate these phenomena: the indirect electrooxidation of di-ketone-L-sorbose into the corresponding ketogulonic acid and the direct electroreduction of acetophenone into pinacol.

Journal Article↗
PubMed2003

New quinoproteins in oxidative fermentation.

Several quinoproteins have been newly indicated in acetic acid bacteria, all of which can be applied to fermentative or enzymatic production of useful materials by means of oxidative fermentation. (1) D-Arabitol dehydrogenase from Gluconobacter suboxydans IFO 3257 was purified from the bacterial membrane and found to be a versatile enzyme for oxidation of various substrates to the corresponding oxidation products. It is worthy of notice that the enzyme catalyzes D-gluconate oxidation to 5-keto-D-gluconate, whereas 2-keto-D-gluconate is produced by a flavoprotein D-gluconate dehydrogenase. (2) Membrane-bound cyclic alcohol dehydrogenase was solubilized and purified for the first time from Gluconobacter frateurii CHM 9. When compared with the cytosolic NAD-dependent cyclic alcohol dehydrogenase crystallized from the same strain, the reaction rate in cyclic alcohol oxidation by the membrane enzyme was 100 times stronger than the cytosolic NAD-dependent enzyme. The NAD-dependent enzyme makes no contribution to cyclic alcohol oxidation but contributes to the reduction of cyclic ketones to cyclic alcohols. (3) Meso-erythritol dehydrogenase has been purified from the membrane fraction of G. frateurii CHM 43. The typical properties of quinoproteins were indicated in many respects with the enzyme. It was found that the enzyme, growing cells and also the resting cells of the organism are very effective in producing L-erythrulose. Dihydroxyacetone can be replaced by L-erythrulose for cosmetics for those who are sensitive to dihydroxyacetone. (4) Two different membrane-bound D-sorbitol dehydrogenases were indicated in acetic acid bacteria. One enzyme contributing to L-sorbose production has been identified to be a quinoprotein, while another FAD-containing D-sorbitol dehydrogenase catalyzes D-sorbitol oxidation to D-fructose. D-Fructose production by the oxidative fermentation would be possible by the latter enzyme and it is superior to the well-established D-glucose isomerase, because the oxidative fermentation catalyzes irreversible one-way oxidation of D-sorbitol to D-fructose without any reaction equilibrium, unlike D-glucose isomerase. (5) Quinate dehydrogenase was found in several Gluconobacter strains and other aerobic bacteria like Pseudomonas and Acinetobacter strains. It has become possible to produce dehydroquinate, dehydroshikimate, and shikimate by oxidative fermentation. Quinate dehydrogenase was readily solubilized from the membrane fraction by alkylglucoside in the presence of 0.1 M KCl. A simple purification by hydrophobic chromatography gave a highly purified quinate dehydrogenase that was monodispersed and showed sufficient purity. When quinate dehydrogenase purification was done with Acinetobacter calcoaceticus AC3, which is unable to synthesize PQQ, purified inactive apo-quinate dehydrogenase appeared to be a dimer and it was converted to the monomeric active holo-quinate dehydrogenase by the addition of PQQ.

Alcohol Oxidoreductases↗
PubMed1982

The biotyping of Escherichia coli isolated from healthy farm animals.

A total of 2973 Escherichia coli, isolated from six different groups of animals, were examined for their ability to ferment adonitol, dulcitol, raffinose, rhamnose and sorbose in solid media. Twenty-nine fermentation patterns were recorded although 2443 (82%) of the E. coli belonged to seven of the 32 possible biotypes. Ninety-six O-serotypes were identified within the 2973 E. coli. The number of O-serotypes represented in the 15 most common biotypes ranged from three to 15. Serotypes O8 and O9 were found most commonly in the different groups of animals and several biotypes amongst these two O-serotypes were identified in two or more groups of the animals. The ability of the E. coli to metabolize aesculin, ornithine, salicin and sucrose was also assessed. These test proved less reproducible and were not included in the primary biotyping scheme although their use allowed the enumeration of additional biotypes. The application of biotyping to the study of the ecology of drug-resistant strains of E. coli in five situations is briefly presented.

Amino Acids↗
PubMed1993

A miniaturized biotyping system for strain discrimination in Escherichia coli.

A two-tier miniaturized scheme of eight tests was devised for biotyping strains of Escherichia coli in microwell plates. Primary biotypes were defined by positive and negative reactions in tests for fermentation of raffinose, sorbose, dulcitol and 2-deoxy-D-ribose and for decarboxylation of ornithine when read after specified periods of incubation; subtypes were identified within primary biotypes according to results in secondary tests for rhamnose fermentation, lysine decarboxylation and motility. The method gave reproducible results on different occasions of testing. Among 100 E. coli strains from various sources, 26 of the 32 possible primary biotypes and 56 full biotypes, as defined by results in both primary and secondary tests, were identified, thus demonstrating a high index of strain discrimination (D = 0.98). The scheme is recommended as a simple, reliable, inexpensive and efficient method of differentiating strains of E. coli.

Bacterial Typing Techniques↗
PubMed1983

A process related to membrane potential involved in bacterial chemotaxis to galactose.

Attractants, in the presence of respiration and ATPase inhibitors, stimulate a hyperpolarization in Escherichia coli [Eisenbach, M. (1982) Biochemistry 21, 6818-6825]. In order to examine whether this hyperpolarization is correlated with chemotaxis, the effect of the attractant D-galactose and its analogues on the membrane potential of wild-type E. coli strains and some of their mutants was studied. The main observations were the following: (i) Wild-type cells became hyperpolarized by either galactose or its nonmetabolizable analogues, D-fucose and L-sorbose. (ii) A mutant defective in galactose metabolism became hyperpolarized by galactose. (iii) Inhibiting the galactose permease system did not prevent the hyperpolarization, rather it facilitated the observation of the hyperpolarization. (iv) Mutants unable to transport galactose via the methyl beta-galactoside (Mgl) transport system but having normal chemotaxis to galactose became normally hyperpolarized by D-fucose. (v) Mutants which cannot bind galactose were not hyperpolarized by galactose. (vi) The hyperpolarization in flaI mutants, in which the whole chemotaxis machinery is repressed, was reduced to 12-15% of the hyperpolarization in the parent strains. (vii) Nonattractant sugars did not stimulate hyperpolarization. It is concluded that the hyperpolarization is the consequence of neither galactose metabolism nor transport but rather is correlated with galactose taxis.

Calcium-Binding Proteins↗
PubMed1986

Carbohydrate substrate specificity of bacterial and plant pyrophosphate-dependent phosphofructokinases.

Pyrophosphate-dependent phosphofructokinase from the facultative anaerobic bacterium Propionibacterium freudenreichii and from the mung bean Phaseolus aureus has been purified to homogeneity. Potential utilization of carbohydrate substrate analogues for each enzyme was initially screened by using Fourier transform 31P NMR at pH 8 and 25 degrees C and monitoring the appearance of the phosphate resonance in the direction of D-fructose 6-phosphate phosphorylation (forward reaction direction) and, with the bisphosphate analogues, the appearance of the pyrophosphate resonance in the direction of phosphate phosphorylation (reverse reaction direction). Both enzymes are strict in their requirements for the sugar phosphate substrate, with only D-fructose 6-phosphate, D-sedoheptulose 7-phosphate, and 2,5-anhydro-D-mannitol 6-phosphate, or their respective bisphosphates in the reverse reaction direction, utilized as substrates at detectable levels. The dissociation constants for D-psicose 6-phosphate, D-tagatose 6-phosphate, and L-sorbose 6-phosphate are an order of magnitude larger than that for D-fructose 6-phosphate, indicating a stringent steric requirement for the D-threo (trans) configuration at the two nonanomeric furan ring hydroxyl groups. These results strongly suggest that the anomeric, epimeric, and tautomeric form of the sugar phosphate substrates favored by both enzymes is the beta-D-fructofuranose form. Dissociation constants for nonsubstrate analogues were used to provide information on the nature of the active site. Competitive inhibition patterns vs. fructose 1,6-bisphosphate were obtained for a series of 1,n-alkanediol bisphosphates (where n = 2-9).(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrates↗
PubMed1979

Carbon-13-enriched carbohydrates: preparation of triose, tetrose, and pentose phosphates.

Three-, four-, and five-carbon aldononitrile phosphates were prepared, purified, and catalyticlly reduced with palladium--barium sulfate (5%) to the corresponding aldose phosphates in high yields at pH 1.7 +/- 0.1 and atmopsheric pressure. DL-Glyceraldehyde 3-phosphate and the tetrose 4-phosphates were prepared with carbon-13 enrichment at C-1, while the pentose 5-phosphates were prepared with enrichment at C-1 and C-2. Preparations of glycolaldehyde phosphate and d-glyceraldehyde 3-phosphate by lead tetra-acetate oxidation of glycerol phosphate and fructose 6-phosphate, respectively, are described. The proportions of cyclic hemiacetals and linear gem-diol forms of the two- to five-carbon aldose phosphates in aqueous solution are reported. Carbon-13 chemical shifts and carbon--phosphorus and carbon--hydrogen coupling constants for the furanose phosphate ring and linear gem-diol phosphates are reported and discussed. d-[2(-13)C]Ribulose 1,5-bisphosphate and L-[3,4(-13)C]sorbose 1,6-bisphosphate were prepared enzymatically from D-[2(-13)C]ribose 5-phosphate and dl-[1(-13)C]glyceraldehyde 3-phosphate, respectively.

Carbohydrate Epimerases↗
PubMed1977

Bovine liver fructokinase: purification and kinetic properties.

Fructokinase from beef liver has been purified 2300-fold by acid and heat treatment, ammonium sulfate fractionation, and chromatography on Sephadex G-100, DEAE- and CM-cellulose. The purified enzyme is homogeneous by all criteria examined, has a molecular weight of 56 000, and is a dimer of equal molecular weight subunits. The isoelectric point is 5.7. The Michaelis constant for activation by K+ is 15 mM, and the enzyme is also activated by Na+, Rb+, Cs+, NH4+, and TL+. The kinetic mechanism has been determined at pH 7.0, 25 degrees C. The initial velocity, product, and dead-end inhibition patterns for CrATP, CrADP, and 1-deoxy-D-fructose are consistent with a random kinetic mechanism with the formation of two dead-end complexes. Substrates for fructokinase include: D-fructose, L-sorbose, D-tagatose, D-psicose, D-xylulose, L-ribulose, D-sedoheptulose, L-galactoheptulose, D-mannoheptulose, 5-keto-D-fructose, D-ribose, 2,5-anhydro-D-mannitol, 2,5-anhydro-D-glucitol, 2,5-anhydro-D-mannose, 2,5-anhydro-D-lyxito.l, and D-ribono-gamma-lactone. 5-Thio-D-fructose was not a substate, but was a competitive inhibitor vs. D-fructose. Thus the minimum molecular for substrate activity seems to be (2R)-2-hydroxy-methyl-3,4-dihydroxytetrahydrofuran. The configuration of the substituents at carbons 3, 4, and 5 appears not to be critical, but the hydroxymethyl group must have the configuration corresponding to beta-D-(or alpha-L-) keto sugars. The anomeric hydroxyl on carbon 2 is not required (although it contributes to binding), and a wide variety of groups may be present at carbon 5.

Animals↗
PubMed2002

The missing link in the fungal L-arabinose catabolic pathway, identification of the L-xylulose reductase gene.

The fungal L-arabinose pathway consists of five enzymes, aldose reductase, L-arabinitol 4-dehydrogenase, L-xylulose reductase, xylitol dehydrogenase, and xylulokinase. All the genes encoding the enzymes of this pathway are known except for that of L-xylulose reductase (EC 1.1.1.10). We identified a gene encoding this enzyme from the filamentous fungus Trichoderma reesei (Hypocrea jecorina). The gene was named lxr1. It was overexpressed in the yeast Saccharomyces cerevisiae, and the enzyme activity was confirmed in a yeast cell extract. Overexpression of all enzymes of the L-arabinose pathway in S. cerevisiae led to growth of S. cerevisiae on L-arabinose; i.e., we could show that the pathway is active in a heterologous host. The lxr1 gene encoded a protein with 266 amino acids and a calculated molecular mass of 28 428 Da. The LXRI protein is an NADPH-specific reductase. It has activity with L-xylulose, D-xylulose, D-fructose, and L-sorbose. The highest affinity is toward L-xylulose (K(m) = 16 mM). In the reverse direction, we found activity with xylitol, D-arabinitol, D-mannitol, and D-sorbitol. It requires a bivalent cation for activity. It belongs to the protein family of short chain dehydrogenases. The enzyme is catalytically similar and homologous in sequence to a D-mannitol:NADP 2-dehydrogenase (EC 1.1.1.138).

Amino Acid Sequence↗