Isolation and characterization of L-fucose dehydrogenase from rabbit liver

L-Fucose dehydrogenase [EC 1.1.1.122] was isolated from a rabbit liver extract and purified about 390-fold with a yield of approximately 13%. The purification procedures included treatment with protamine, ammonium sulfate fractionation, treatment with acid, DE-32 celluose colum chromatography, gel filtration on Sephadex G-100, preparative polyacrylamide gel electrophoresis, and affinity chromatography on 5' AMP-Sepharose 4B. The last procedure, affinity chromatography on 5' AMP-Sephadex 4B, was useful for the removal of other dehydrogenases. The eznyme which was homogeneous, as shown by polyacrylamide gel electrophoresis, had a molecular weight of about 92,000. The optimum pH was at 10.0 and isoelectric point at 5.2. The enzyme accepted both L-fucose and D-arabinose as substrate, but was specific for NAD+ as coenzyme. Km values were 0.15 mM, 1.4 mM, and 0.7 mM for L-fucose, D-arabinose, and NAD+, respectively. A single enzyme catalyzed the oxidation of L-fucose and D-arabinose, which had the same configurations of hydroxyl groups from C-2 to C-4. The reaction products obtained with L-fucose as substrate were L-fucono-lactone and L-fuconic acid. The L-fucono-lactone was an immediate product of oxidation and was hydrolyzed to L-fuconic acid spontaneously. This reaction was irreversible. Therefore, it is likely that L-fucose dehydrogenase is involved in the initial step of the catabolic pathway of L-fucose in rabbit liver.     

Hydrophobic-ionic chromatography. Its application to purification of porcine pancreas enzymes.

1. All the porcine pancreas enzymes tested, regardless of their pI's were adsorbed on Amberlite CG-50 (a weakly acidic cation exchange resin) at pH 4, where the ion-exchange group (carboxyl group) is not dissociated. The adsorption is hardly influenced by ionic strength. 2. At pH 4, the adsorbed enzymes were partially eluted by organic solvents such as 50% propanol. 3. The adsorbed enzymes were effectively eluted by increasing the pH from 4 to 6. Trypsin (pI 10.5) was eluted before carboxypeptidase A (pI 4.5 AND 5.3) WITH 0.5 M acetate buffer, whereas the former enzyme was eluted after the latter enzyme with 0.2 M 3,3-dimethyl glutarate buffer. However, with either buffer, the elution order of enzymes was not always the same as the order of the pI's. 4. By a single Amberlite CG-50 column chromatography of porcine pancreas extracts, kallikrein, carboxypeptidase B, deoxyribonuclease, carboxypeptidase A, and trypsin were purified 100-fold, 16-fmately 13%. The purification procedures included treatment with protamine, ammonium sulfate fractionation, treatment with acid, DE-32 cellulose column chromatography, gel filtration on Sephadex G-100, preparative polyacrylamide gel electrophoresis, and affinity chromatography on 5' AMP-Sepharose 4B. The last procedure, affinity chromatography on 5' AMP-Sepharose 4B, was useful for the removal of other dehydrogenases. The enzyme which was homogeneous, as shown by polyacrylamide gel electrophoresis, had a molecular weight of about 92,000. The optimum pH was at 10.0 and isoelectric point at 5.2. The enzyme accepted both L-fucose and D-arabinose as substrate, but was specific for NAD+ as coenzyme. Km values were 0.15 mM, 1.4 mM, and 0.07 mM for L-fucose, D-arabinose, and NAD+, respectively. A single enzyme catalyzed the oxidation of L-fucose and D-arabinose, which had the same configurations of hydroxyl groups from C-2 to C-4. The reaction products obtained with L-fucose as substrate were L-fucono-lactone and L-fuconic acid. The L-fucono-lactone was an immediate product of oxidation and was hydrolyzed to L-fuconic acid spontaneously. This reaction was irreversible. Therefore, it is likely that L-fucose dehydrogenase is involved in the initial step of the catabolic pathway of L-fucose in rabbit liver.     

Anomeric specificity of L-fucose dehydrogenase: a stereochemical imperative in aldopyranose dehydrogenases?

A set of hypotheses is proposed that explains the anomeric specificity of aldopyranose dehydrogenases in terms of an evolutionarily selected function. The first hypothesis, based on stereoelectronic theory, argues that, in the "allowed" transition state for oxidation at the anomeric carbon, the two oxygens attached to the anomeric carbon each bear a lone pair of electrons antiperiplanar to the departing "hydride". The second hypothesis is that the dehydrogenase is functionally constrained to bind the anomer that has this arrangement of lone pairs in its lowest energy chair conformer. The anomeric specificity of L-fucose dehydrogenase is experimentally examined. The enzyme oxidizes preferentially the beta-anomer, consistent with the prediction made by these hypotheses. Available experimental data for other enzymes (D-glucose-6-phosphate dehydrogenase, D-glucose dehydrogenase, D-galactose dehydrogenase, D-abequose dehydrogenase, and D-arabinose dehydrogenase) are found to be also consistent with the proposed hypotheses.     

L-fucose metabolism in mammals. Kinetic studies on pork liver 2-keto-3-deoxy-L-fuconate:NAD+ oxidoreductase.

Pork liver 2-keto-3-deoxy-L-fuconate:NAD+ oxidoreductase has been shown to convert 2-keto-3-deoxy-L-fuconate to a 6-carbon acid tentatively identified as 2,4(or 5)-diketo-5(or 4)-monohydroxyhexanoate. The enzyme has a pH optimum of 10. 5 or higher. It is stabilized by dithiothereitol and inhibited by p-hydroxymercuribenzoate and heavy metals (Ag+, Hg2+, Co2+, Cd2+, Pb2+, Zn2+, and Cu2+), suggesting the presence of a functionally essential sulfhydryl group; pre-treatment of enzyme with NAD+ prevents inhibition by p-hydrocymercuribenzoate and heavy metals indicating that this sulfhydryl group may be near the NAD+ binding site. The enzyme has an absolute requirement for NAD+; NADP+ is an ineffective coenzyme. Several lines of evidence indicate that the same enzyme acts on both 2-keto-3-deocy-L-fuconate and 2-keto-3-deoxy-D-arabonate; thus, the pure enzyme acts on both substrates, the two substrates have very similar kinetic parameters (Km values are: 2-keto-3-deocy-L-fuconate, 0.20 mM; 2-keto-3-deoxy-D-arabonate, 0.25 mM; NAD+ for either substrate, 0.22 to 0.25 mM), the two substrates show identical pH and temperature profiles and the two substrates compete for common enzyme active sites. A large number of other sugars and sugar acids, including several 2-keto-3-deoxyaldonates, were ineffective as substrates. The dehydrogenase was also found in calf, beef, lamb, mouse, and rat liver. These studies when considered together with previous studies on the metabolism of L-fucose in pork liver indicate the presence of a soluble enzyme pathway capable of converting L-fucose to 2,4(or 5)-diketo-5(or 4)-monohydroxyhexanoate; this pathway can also convert D-arabinose, and probably L-galactose, to the analogous derivatives (diketomonohydroxypentanoate and diketodihydroxyhexanoate, respectively.     

Characterisation and biosynthesis of D-erythroascorbic acid in Phycomyces blakesleeanus

D-Erythroascorbate and D-erythroascorbate glucoside have been identified in the Zygomycete fungus Phycomyces blakesleeanus. Ascomycete and Basidiomycete fungi also synthesise D-erythroascorbate instead of l-ascorbate, suggesting that D-erythroascorbate synthesis evolved in the common ancestor of the fungi. Both compounds accumulate in P. blakesleeanus at higher levels than observed in other fungal species. D-Erythroascorbate glucoside reduced dichlorophenolindophenol as effectively as L-ascorbate, but was more stable to autoxidation. D-Erythroascorbate glucoside predominated in spores and stationary phase mycelium. Free D-erythroascorbate accumulated during the exponential phase of mycelial growth and decreased to very low levels in the stationary phase. This suggests an association between growth and free D-erythroascorbate. P. blakesleeanus converted exogenous D-arabinose to D-erythroascorbate and its glucoside. A monomeric NAD-dependent D-arabinose dehydrogenase of 41 kDa was purified to near homogeneity. The enzyme oxidised D-arabinose, L-galactose, and L-fucose. Correspondingly, mycelium converted exogenous L-galactose and L-fucose to L-ascorbate and 6-deoxyascorbate, respectively. The antioxidant role of D-erythroascorbate and its glucoside is discussed.     

A simple one-pot method for the synthesis of partially protected mono- and disaccharide building blocks using an orthoesterification-benzylation-orthoester rearrangement approach

A simple one-pot method is reported for making partially protected glycosyl acceptors from O-methyl or S-alkyl/aryl glycosides of D-glucose, D-galactose, D-arabinose, L-rhamnose, L-fucose and lactose via orthoester formation, benzylation and selective hydrolysis.     

Natural and altered induction of the L-fucose catabolic enzymes in Klebsiella aerogenes.

Mutants of Klebsiella aerogenes W70 were isolated that had gained the ability to utilize the uncommon pentose D-arabinose as their sole source of carbon and energy. In contrast to the D-arabinose-negative, parent strain, these mutants were found to be either constitutive for certain enzymes of the L-fucose catabolic pathway or inducible for such enzymes when incubated in the presence of D-arabinose. The mutants used L-fucose isomerase to convert D-arabinose to D-ribulose, which is an intermediate and inducer of the ribitol catabolic pathway. The D-ribulokinase of the ribitol pathway was then induced. This enzyme catalyzed the phosphorylation of D-ribulose at the 5-carbon position. Mutants that were negative for D-ribulokinase could still dissimilate D-arabinose slowly by using all three enzymes, the isomerase, kinase, and aldolase, of the L-fucose pathway. Using condition negative mutants, we were able to demonstrate that the natural induction of the L-fucose pathway enzymes by L-fucose required the activity of a functional L-fucose isomerase and a functional L-fuculokinase but not an L-fuculose-1-phosphate aldolase. A metabolic intermediate, L-fuculose-1-phosphate, was thereby shown to be a probable inducer of at least the isomerase and kinase of the L-fucose catabolic pathway. Similar experiments, with D-arabinose-positive mutants, which were induced for the L-fucose pathway enzymes upon incubation with D-arabinose, revealed that the activities of the L-fucose isomerase and the L-fuculokinase were also required for the induction of the L-fucose enzymes. These D-arabinose-positive mutants apparently produced an altered regulatory protein that accepted both L-fuculose-1-phosphate and D-ribulose-1-phosphate as inducers. Examination of constitutive mutants revealed that L-fucose isomerase and L-fuculokinase were both synthesized constitutively, with the aldolase apparently under separate control.     

Screening of basidiomycete fungi for the quinone-dependent sugar C-2/C-3 oxidoreductase, pyranose dehydrogenase, and properties of the enzyme from Macrolepiota rhacodes

Mycelial cultures of 76 strains of lignocellulose-degrading basidiomycete fungi were screened for the activity of pyranose dehydrogenase, a novel sugar oxidoreductase recently detected in Agaricus bisporus. Of these fungi, 37 strains belonging to seven phylogenetically related genera of mostly litter-decomposing Agaricales were positive for the dehydrogenase, based on activity assays towards D-glucose with 1,4-benzoquinone or ferricenium ion as electron acceptors, and on TLC/HPLC analyses of the reaction products. Lack of activity with O(2) as the oxidant, specificity for C-3 of D-glucose, and active extracellular secretion of the enzyme were used as criteria to differentiate pyranose dehydrogenase from pyranose 2-oxidase (EC 1.1.3.10), known to be produced by numerous wood-rotting fungi. Extracellular pyranose dehydrogenase from Macrolepiota rhacodes was heavily glycosylated. The enzyme was characterized as a 78-kDa flavoprotein under denaturing conditions and a 76-kDa native protein using gel filtration. This enzyme had a maximum extracellular activity of 4.1 U ml(-1) in 39-day liquid cultures. It exhibited broad selectivity for sugar substrates and oxidized D-glucose (K(m)=1.82) exclusively at C-3 to 3-dehydro-D-glucose (D-ribo-hexos-3-ulose), in contrast to pyranose dehydrogenases from Agaricus species, which acted at both C-3 and C-2 of D-glucose. The N-terminal sequence, AVVYRHPDEL, showed significant similarity with that reported for A. bisporus.     

Glucose transfer across the intact guinea-pig placenta

Experiments were carried out in anaesthetized pregnant guinea-pigs. Following the maternal injection of a bolus containing 14C-hexose and 3H2O, blood was sampled from the fetal umbilical vein during a single circulatory transit. A placental transfer index was calculated from the ratio of the tracers in the fetal whole blood divided by that in maternal plasma. The transfer index for D-glucose, 0.66 +/- 0.03 (SEM), greatly exceeded that for L-glucose, 0.013 +/- 0.004. Elevation of the maternal plasma D-glucose concentration, with unlabelled D-glucose, resulted in saturation of D-glucose transfer with an apparent Km of 1.2 x 10(-2) mol/l mean maternal plasma D-glucose. Phlorizin at maternal plasma concentrations of approximately 10(-3) mol/l inhibited D-glucose transfer by 40%. Phloretin did not affect D-glucose transfer at levels estimated to be 10(-4) mol/l. Specificity studies with substituted D-glucose analogues showed that alpha-methyl-D-glucoside is not transported by a facilitated pathway; 2-deoxy-D-glucose and 3-O-methyl-D-glucose share the D-glucose carrier and D-galactose has a partial affinity for the D-glucose carrier.     

A new and efficient strategy for the synthesis of shimofuridin analogs: 2'-O-(4-O-stearoyl-alpha-L-fucopyranosyl)thymidine and -uridine

Two shimofuridin analogs: 2'-O-(4-O-stearoyl-alpha-L-fucopyranosyl)thymidine (2) and -uridine (3) have been synthesized using D-arabinose, L-fucose, thymine, uracil, and stearoyl chloride as the starting materials. The synthetic procedures involve the facile preparation of 1-(3,5-di-O-benzyl-beta-D-ribofuranosyl)thymine (9) and -uracil (10) by coupling of 1,2-anhydro-3,5-di-O-benzyl-alpha-D-ribofuranose (8) with silylated thymine and uracil, and then stereoselective formation of the 1,2-cis (alpha) interglycoside bonds through condensation of the nucleoside derivatives 9 and 10 with 2-(2,3-di-O-benzyl-4-O-stearoyl-beta-L-fucopyranosylsulfonyl) pyrimidine (18). The 1,2-anhydro-3,5-di-O-benzyl-alpha-D-ribofuranose (8) was prepared by an improved procedure from D-arabinose.     

A comparison of alternate metabolic strategies for the utilization of D-arabinose

Summary Mutants ofKlebsiella aerogenes W70 that metabolize the uncommon pentose D-arabinose were isolated. These mutants were found to be either constitutive or indicible by D-arabinose for the synthesis of enzymes in the L-fucose pathway. Such mutants could then utilize L-fucose isomerase to convert the structurally similar D-arabinose molecule to D-ribulose. D-Ribulose is an inter-mediate and the inducer of an existing ribitol pathway and could thus be metabolized. In those D-arabinose-positive mutants where the ribitol pathway was blocked by mutation, D-ribulose could alternatively be metabolized by using the remaining L-fucose pathway enzymes. When the two D-arabinose catabolic routes were compared, catabolism of D-arabinose via the ribitol pathway was found to be more efficient. Catabolism of D-arabinose using the L-fucose pathway per-mitted D-ribulose to escape into the media and produced an unmetabolizable end product, L-glycolic acid. A comparison of growth using constitutive versus inducible control of the borrowed L-fucose isomerase did not reveal an advantage for one control type over the other. Several differences were observed,however, when we determined the degree to which these control mutations perturbed the normal functioning of the L-fucose and associated pathways. Growth of the constitutive mutant was impaired with L-fucose as substrate. The inducible-control mutant had altered growth characteristics on ribitol and L-rhamnose.     

L-fucose metabolism in mammals. Purification of pork liver 2-keto-3-deoxy-L-fuconate:NAD+ oxidoreductase by NAD+-Agarose affinity chromatography.

Pork liver has previously been reported to contain a soluble enzymatic pathway which converts L-fucose to 2-keto-3-deoxy-L-fuconate and D-arabinose to 2-keto-3-deoxy-D-arabonate. We now report the isolation from pork liver of a soluble NAD+-dependent dehydrogenase which acts on both 2-keto-3-deoxy-L-fuconate and 2-keto-3-deoxy-D-arabonate. This enzyme has been purified to homogeneity by a five-step procedure; the final step involved affinity chromatography on NAD+-agarose. A purification factor of about 3000-fold was achieved with a yield of over 20%. The enzyme was homogeneous on polyacrylamide gel electrophoresis at pH 9.1 and 7.0 and on the basis of sedimentation equilibrium analysis with the ultracentrifuge. The molecular weight of the native enzyme is about 100,000 while disc gel electrophoresis in the presence of sodium dodecyl sulfate and thiol showed the presence of a polypeptide of molecular weight 26,800; these results suggest that the enzyme is a tetramer. The enzyme has an isoelectric point of 5.4. The enzyme is unstable in the dilute state and in the absence of thiol but can be kept for 2 years at -70 degrees at a protein concentration of 4 mg per ml and in the presence of 1 mM dithiothreitol.     

Synthesis of sucrose analogues and the mechanism of action of Bacillus subtilis fructosyltransferase (levansucrase)

In the present study, we have coupled detailed acceptor and donor substrate studies of the fructosyltransferase (FTF, levansucrase) (EC 2.4.1.162) from Bacillus subtilis NCIMB 11871, with a structural model of the substrate enzyme complex in order to investigate in detail the roles of the active site amino acids in the catalytic action of the enzyme and the scope and limitation of substrates. Therefore we have isolated the ftf gene, expressed in Escherichia coli, yielding a levansucrase. Consequently, detailed acceptor property effects in the fructosylation by systematic variation of glycoside acceptors with respect to the positions (2, 3, 4 and 6) of the hydroxyl groups from equatorial to axial have been studied for preparative scale production of new oligosaccharides. Such investigations provided mechanistic insights of the FTF reaction. The configuration and the presence of the C-2 and C-3 hydroxyl groups of the glucopyranoside derivatives either as substrates or acceptors have been identified to be rate limiting for the trans-fructosylation process. The rates are rationalized on the basis of the coordination of d-glycopyranoside residues in (4)C(1) conformation with a network of amino acids by Arg360, Tyr411, Glu342, Trp85, Asp247 and Arg246 stabilization of both acceptors and substrates. In addition we also describe the first FTF reaction, which catalyzes the beta-(1-->2)-fructosyl transfer to 2-OH of L-sugars (L-glucose, L-rhamnose, L-galactose, L-fucose, L-xylose) presumably in a (1)C(4) conformation. In those conformations, the L-glycopyranosides are stabilized by the same hydrogen network. Structures of the acceptor products were determined by NMR and mass spectrometry analysis.     

Metal ion- and phosphate-mediated transport of glucose by insulin.

Insulin, in the presence of Mg²⁺ and Pi, can transport D-glucose across a bulk phase separating two aqueous phases. All three molecular species (Mg²⁺, Pi, D-glucose) are transported simulataneously in 1:1:1 stoichiometry. The same system will transport D-galactose and L-arabinose, but not L-glucose, D-arabinose, D-mannitol, D-fructose and 3-0-methyl glucose. Phloridzin completely suppresses transport, not only of glucose, but also of Mg²⁺ and Pi. Other divalent metal ions are less efficient (Mg²⁺ >Mn²⁺ >Ca²⁺ >Zn²⁺). The capability of insulin for transport of D-glucose is not duplicated by proinsulin or glucagon. Amino acids and citric cycle substrates are also transported, some as rapidly as D-glucose. Pi is replaceable by phosphate esters such as AMP, ADP and ATP, less efficiently with Mg²⁺, but more efficiently with Ca²⁺ as metal ion. The transport of D-glucose in the systems formed by insulin, Ca²⁺ and nucleotide is less sensitive to phloridzin than the standard Mg²⁺, Pi system.     

Comparative kinetics of D-xylose and D-glucose isomerase activities of the D-xylose isomerase from Thermus aquaticus HB8

The D-xylose isomerase from T. aquaticus accepts, besides D-xylose, also D-glucose, and, with lower efficiency, D-ribose, and D-arabinose as alternative substrates. The activity of the enzyme is strictly dependent on divalent cations. Mn2+ is most effective in the D-xylose isomerase reaction and Co2+ in the D-glucose isomerization. Mg2+ is active in both reactions, Zn2+ only in the further one. The enzyme is strongly inhibited by Cu2+, and weakly by Ni2+, Fe2+, and Ca2+. A hyperbolic dependence of the reaction velocity of the D-xylose isomerase on the concentration of D-xylose xylose and of D-glucose was found, while biphasic saturation curves were obtained by variation of the metal ion concentrations. The D-glucose isomerization reaction shows normal behaviour with respect to the metal ions. A kinetic model was derived on the basis of the assumption of two binding sites for divalent cations, one cofactor site with higher affinity and a second, low affinity site, which modulates the activity of the enzyme.     

Structural Specificity of Sugar Transport at the Blood-Nerve Barrier

Abstract: The major component of D-glucose transfer across the membranous sites of the blood-nerve barrier (BNB) occurs via a facilitative mechanism at a rate greater than twice the rate of D-glucose metabolism by nerve. To characterize further properties of monosaccharide transport at the BNB, unidirectional transfer constant (K) values were determined in vivo in tibial nerve of anesthetized rats for radiolabeled mannitol, L-glucose, and a series of D-glucose analogs. K values (× 10⁻⁴ ml s⁻¹ g^−l) equaled 4.8 for 2-deoxy-D-glucose, 3.7 for D-glucose, 2.3 for 3- O -methyl-D-glucose, 1.4 for D-man-nose, 0.6 for D-galactose, 0.2 for mannitol, and 0.19 for L-glucose. The rank order of ratios between K values of a D-hexose and D-glucose, which reflects the rank order of affinity of the system for individual sugars, was 2-deoxy-D-glucose > D-glucose > 3-O-methyl-D-glucose > D-mannose > D-galactose. The results demonstrate that the order of substrate affinity of the monosaccharide carrier at the BNB is similar to that at cerebral capillaries and at erythrocytes. At normal concentrations of plasma D-glucose, the contribution of simple passive diffusion to unidirectional D-glucose influx across the BNB equals 5%, which is greater than that at cerebral capillaries and reflects the greater permeability to hydrophilic nonelectrolytes of the endoneurial vasculature.     

L-glucose absorption in house sparrows (<Emphasis Type="Italic">Passer domesticus</Emphasis>) is nonmediated

We previously demonstrated in intact house sparrows substantial absorption in vivo of L-glucose, the stereoisomer of D-glucose that is assumed not to interact with the intestines D-glucose transporter. Results of some studies challenge this assumption for other species. Therefore, we tested it in vitro and in vivo, based on the principle that if absorption of a compound (L-glucose) is mediated, then absorption of its tracer will be competitively inhibited by high concentrations of either the compound itself or other compounds (e.g., D-glucose) whose absorption is mediated by the same mechanism. An alternative hypothesis that L-glucose absorption is primarily paracellular predicts that its absorption in vivo will be increased (not decreased) in the presence of D-glucose, because the permeability of this pathway is supposedly enhanced when Na⁺-coupled glucose absorption occurs. First, using intact tissue in vitro, we found that uptake of tracer-radiolabeled L-glucose was not significantly inhibited by high concentrations (100 mM) of either L-glucose or 3-O-methyl-D-glucose, a non-metabolizable but actively transported D-glucose analogue. Second, using intact house sparrows, we found that fractional absorption of the L-glucose tracer was significantly increased, not reduced, when gavaged along with 200 mM 3-O-methyl-D-glucose. This result was confirmed in another experiment where L-glucose fractional absorption was significantly higher in the presence vs. absence of food in the gut. The greater absorption was apparently not due simply to longer retention time of digesta, because no significant difference was found among retention times. Our results are consistent with the idea that L-glucose is absorbed in a non-mediated fashion, largely via the paracellular pathway in vivo.Abbreviations AUC area under the curve - 3OMD-glucose 3-O-methyl-D-glucose Communicated by I.D. Hume     

Cloning of D-glucose dehydrogenase with a narrow substrate specificity fromBacillus thuringiensis M15

We have cloned an ORF ofBacillus thuringiensis M15, which encodes a protein sharing high similarity with D-glucose dehydrogenase. A high-expression plasmid (pBtGDH) for the ORF was constructed.Escherichia coli JM 109 transformed with pBtGDH exhibited D-glucose dehydrogenase activity, and the enzyme was purified by 3 chromatographic steps to homogeneity with 6.9 fold and a final yield of 13%. The purified enzyme has highly narrow substrate specificity for glucose and 2-deoxy-D-glucose and showed no activity with any other sugars we tested. The properties of the purified enzyme were similar to those of the D-glucose dehydrogenase (BtGDH) that is mainly produced inB. thuringiensis M15. These results show that the cloned gene encodes BtGDH, as we previously reported. This is the first report to determine the sequence of the enzyme with narrow substrate specificity. BtGDH shows 89% sequence similarity with D-glucose dehydrogenase fromBacillus megaterium IWG3 (GDH-IWG3), which has broad substrate specificity. A comparative analysis between BtGDH and GDH-IWG3 will reveal the differences between them and show the narrow specific activity of BtGDH.     

High shikimate production from quinate with two enzymatic systems of acetic acid bacteria

3-Dehydroshikimate was formed with a yield of 57-77% from quinate via 3-dehydroquinate by two successive enzyme reactions, quinoprotein quinate dehydrogenase (QDH) and 3-dehydroquinate dehydratase, in the cytoplasmic membranes of acetic acid bacteria. 3-Dehydroshikimate was then reduced to shikimate (SKA) with NADP-dependent SKA dehydrogenase (SKDH) from the same organism. When SKDH was coupled with NADP-dependent D-glucose dehydrogenase (GDH) in the presence of excess D-glucose as an NADPH re-generating system, SKDH continued to produce SKA until 3-dehydroshikimate added initially in the reaction mixture was completely converted to SKA. Based on the data presented, a strategy for high SKA production was proposed.