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At least 19 recordsLinked to original sources
PubMed1992

Active site similarities of glucose dehydrogenase, glucose oxidase, and glucoamylase probed by deoxygenated substrates.

The specificity constants, kcat/KM, were determined for glucose oxidase and glucose dehydrogenase using deoxy-D-glucose derivatives and for glucoamylase using deoxy-D-maltose derivatives as substrates. Transition-state interactions between the substrate intermediates and the enzymes were characterized by the observed kcat/Km values and found to be very similar. The binding energy contributions of individual sugar hydroxyl groups in the enzyme/substrate complexes were calculated using the relationship delta(delta G) = -RT ln [(kcat/KM)deoxy/(kcat/KM)hydroxyl] for the series of analogues. The activity of all three enzymes was found to depend heavily on the 4- and 6-OH groups (4'- and 6'-OH in maltose), where changes in binding energies from 10 to 18 kJ/mol suggested strong hydrogen bonds between the enzymes and these substrate OH groups. The 3-OH (3'-OH in maltose) was involved in weaker interactions, while the 2-OH (2'-OH in maltose) had a very small if any role in transition-state binding. The three enzyme-substrate transition-state interactions were compared using linear free energy relationships (Withers, S. G., & Rupitz, K. (1990) Biochemistry 29, 6405-6409) in which the set of kcat/KM values obtained with substrate analogues for one enzyme is plotted against the corresponding values for a second enzyme. The high linear correlation coefficients (rho) obtained, 0.916, 0.958, and 0.981, indicate significant similarity in transition-state interactions, although the three enzymes lack overall sequence homology.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Glucose dehydrogenase, glucose-6-phosphate dehydrogenase and hexokinase in liver of rainbow trout (Salmo gairdneri). Effects of starvation and temperature variations.

1. Activities of trout liver glucose dehydrogenase (GDH, EC 1.1.1.47) and glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) were increased after a sudden drop in water temperature, but not in long-time cold acclimated as compared with warm acclimated trout. 2. Possibly, the activities of GDH and G6PD were temporarily increased in connection with metabolic adaptation to the lower temperature. 3. The activities of GDH and G6PD were not changed by the stress of handling. 4. Partially purified trout liver GDH has a lower activation energy with glucose than with glucose-6-phosphate as substrate, and the Km (glucose) decreases with decreasing assay temperature. 5. At low temperatures, the activity of trout liver GDH with glucose as substrate may be comparable to that of glucose-6-phosphate. 6. Partially purified beef liver GDH has a high activation energy with glucose as substrate, and the Km (glucose) does not change with the assay temperature. 7. Hexokinase (HK, EC 2.7.1.1) and GDH activities were unchanged when trout were deprived of food for 4 weeks. Apparently, the trout liver glucose utilization did not adapt to the starvation.

Acclimatization↗
PubMed2005

Development of a novel glucose enzyme fuel cell system employing protein engineered PQQ glucose dehydrogenase.

Glucose dehydrogenase harboring pyrroloquinoline quinone as the prosthetic group (PQQGDH) from Acinetobacter calcoaceticus is an ideal enzyme for the anode of biofuel cell, because of its oxygen insensitivity and high catalytic efficiency. However, the application of PQQGDH for the bioanode is inherently limited because of its instability. Using Ser415Cys mutant whose stability was greatly improved, we constructed the biofuel cell system employing the engineered PQQGDH as the bioanode enzyme and bilirubin oxidase (BOD) as the biocathode, and compared the stability of the biofuel cell with that employing wild-type PQQGDH. The maximum power density was 17.6 microW/cm2 at an external optimal load of 200 k omega. Using Ser415Cys mutant, the lifetime of the biofuel cell system was greatly extended to 152 h, more than six times as that of the biofuel cell employing the wild-type.

Acinetobacter calcoaceticus↗
PubMedDate not supplied

6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, glucose-6-phosphate isomerase, and hexokinase activity ratios in some human tumor cytosols.

The ratios of some key enzymatic activities of carbohydrate metabolism have been measured in human tumor cytosols. The activities of whole hexokinase (low Km, EC 2.7.1.1 and high Km, EC 2.7.1.2), 6-phosphogluconate dehydrogenase (EC 1.1.1.43), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and glucose-6-phosphate isomerase (EC 5.3.1.9) change according to a biochemical pattern coherent with cell growth requirements. 6-phosphogluconate dehydrogenase activity was in each sample tested higher than glucose-6-phosphate dehydrogenase activity; this indicates that 6-phosphogluconate, a powerful inhibitor of glucose-6-phosphate isomerase, is unlikely to accumulate and inhibit this enzyme and glucose-6-phosphate channelling into glycolysis.

Cytosol↗
PubMed1999

Human hexose-6-phosphate dehydrogenase (glucose 1-dehydrogenase) encoded at 1p36: coding sequence and expression.

Using the published protein sequence from a rabbit microsomal glucose-6-phosphate dehydrogenase G6PD we have isolated and sequenced a cDNA clone coding for its human equivalent, which is also known as hexose-6-phosphate dehydrogenase (H6PD) and glucose dehydrogenase. The corresponding genomic sequence is in the databases enabling its localization to chromosome 1p36. The gene spans 37 kb and consists of 5 exons, the fifth of which codes for more than half of the 89 kDa protein. The first intron is a 10 kb insertion in the 5' untranslated sequence. The predicted mRNA has an exceptionally long (6.5 kb) 3' untranslated sequence. The predicted protein shows extensive homology with X-linked G6PD, suggesting the two genes share a common ancestor but no intron positions are conserved between the two genes suggesting the gene duplication was an ancient event. The C-terminal portion of the protein is not homologous with G6PD but shows limited homology with proteins of unknown function found throughout evolution and encoded next to G6PD in various micro-organisms. Intriguingly this C-terminal portion has some homology with the N-terminal sequence of Plasmodium falciparum G6PD.

Amino Acid Sequence↗
PubMed1999

Continuous production of L-carnitine with NADH regeneration by a nanofiltration membrane reactor with coimmobilized L-carnitine dehydrogenase and glucose dehydrogenase.

L-carnitine dehydrogenase (CDH) was partially purified from Pseudomonas putida IAM12014 for the stereospecific reduction of 3-dehydrocarnitine to L-carnitine. CDH and glucose dehydrogenase (GDH) were coimmobilized in a nanofiltration membrane bioreactor (NFMBR) for the continuous production of L-carnitine from 3-dehydrocarnitine with NADH regeneration. In the NFMBR, NAD was partially immobilized through rejection by the nanofiltration membrane and effectively regenerated by the conjugation reaction of CDH and GDH. Since 3-dehydrocarnitine was unstable at neutral pH, it was maintained under acidic conditions (pH 0.7) and supplied to the NFMBR separately from the other substrates, glucose and coenzyme NAD. As 50 mM 3-dehydrocarnitine in HCl solution, 0.05 mM NAD, and 100 mM glucose in 0.5 M Tris buffer (pH 8) were continuously supplied to the NFMBR with immobilized CDH (200 U/ml) and GDH (200 U/ml) at the retention time of 80 min and temperature of 25 degrees C, the maximum conversion, reactor productivity, and NAD regeneration number were 78%, 113 g/l/d, and 780, respectively. The half-life of the NFMBR was longer than 500 h.

Journal Article↗
PubMed1976

Specific activities of 6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase and glucose-6-phosphate isomerase during Bufo bufo development.

It has been suggested by some authors that during amphibian development, due to the higher glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activity compared to that of 6-phosphogluconate dehydrogenase (EC 1.1.1.43), 6-phosphogluconate could accumulate in the embryo tissues and regulate the channelling of glucose-6-phosphate into glycolysis. Here, on the base of the specific activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and glucose-6-phosphate isomerase (EC 5.3.1.9) found in the embryos of Bufo bufo during development, it is discussed whether 6-phosphogluconate can accumulate and play a regulative role on glucose-6-phosphate metabolism in the anuran embryo.

Animals↗
PubMed2004

Determination of enzyme mechanisms by molecular dynamics: studies on quinoproteins, methanol dehydrogenase, and soluble glucose dehydrogenase.

Molecular dynamics (MD) simulations have been carried out to study the enzymatic mechanisms of quinoproteins, methanol dehydrogenase (MDH), and soluble glucose dehydrogenase (sGDH). The mechanisms of reduction of the orthoquinone cofactor (PQQ) of MDH and sGDH involve concerted base-catalyzed proton abstraction from the hydroxyl moiety of methanol or from the 1-hydroxyl of glucose, and hydride equivalent transfer from the substrate to the quinone carbonyl carbon C5 of PQQ. The products of methanol and glucose oxidation are formaldehyde and glucolactone, respectively. The immediate product of PQQ reduction, PQQH- [-HC5(O-)-C4(=O)-] and PQQH [-HC5(OH)-C4(=O)-] converts to the hydroquinone PQQH2 [-C5(OH)=C4(OH)-]. The main focus is on MD structures of MDH * PQQ * methanol, MDH * PQQH-, MDH * PQQH, sGDH * PQQ * glucose, sGDH * PQQH- (glucolactone, and sGDH * PQQH. The reaction PQQ-->PQQH- occurs with Glu 171-CO2- and His 144-Im as the base species in MDH and sGDH, respectively. The general-base-catalyzed hydroxyl proton abstraction from substrate concerted with hydride transfer to the C5 of PQQ is assisted by hydrogen-bonding to the C5=O by Wat1 and Arg 324 in MDH and by Wat89 and Arg 228 in sGDH. Asp 297-COOH would act as a proton donor for the reaction PQQH(-)-->PQQH, if formed by transfer of the proton from Glu 171-COOH to Asp 297-CO2- in MDH. For PQQH-->PQQH2, migration of H5 to the C4 oxygen may be assisted by a weak base like water (either by crystal water Wat97 or bulk solvent, hydrogen-bonded to Glu 171-CO2- in MDH and by Wat89 in sGDH).

Alcohol Oxidoreductases↗
PubMed1990

The same domain motif for ubiquinone reduction in mitochondrial or chloroplast NADH dehydrogenase and bacterial glucose dehydrogenase.

The respiratory chain NADH:ubiquinone oxidoreductase (NADH dehydrogenase or Complex I) of mitochondria comprises some 30 different subunits, and one FMN and 4 or 5 iron-sulfur clusters as internal redox groups. The bacterial glucose dehydrogenase, which oxidizes glucose to gluconolactone in the periplasmatic space and transfers the electrons to ubiquinone, is a single polypeptide chain with pyrolloquinoline quinone as the only redox group. We report here that the two different enzymes have the same ubiquinone binding domain motif and we discuss the predicted membrane folding of this domain with regard to its role in the proton translocating function of the two enzymes.

Amino Acid Sequence↗
PubMedDate not supplied

[Mechanism of the enzymatic reaction catalyzed by uridine diphosphate glucose dehydrogenase. The chemical synthesis of uridine diphosphate glucose-6-H3 and its oxidation by uridine diphosphate glucose dehydrogenase].

The synthesis of UDP-glucose-6-s-H was performed through condensation of alpha-D-glucopyranosyl phosphate-6-3-H and uridine 5'-phosphomorpholidate. Enzymic oxidation of UDP-glucose-6-3-H with calf liver UDP-glucose dehydrogenase was found to proceed with direct transfer of the hydrogen from C-6 of UDP-glucose onto NAD.

Alcohol Oxidoreductases↗
PubMed1982

Glycerol phosphate dehydrogenase, glucose-6-phosphate dehydrogenase, and lactate dehydrogenase: activities in oligodendrocytes, neurons, astrocytes, and myelin isolated from developing rat brains.

Glycerol phosphate dehydrogenase (GPDH), glucose-6-phosphate dehydrogenase (G6PDH), and lactate dehydrogenase (LDH) activities were determined in oligodendrocytes, neurons, and astrocytes isolated from the brains of developing rats. The activity of each enzyme was significantly lower in both neurons and astrocytes than in oligodendrocytes. The GPDH activity in oligodendrocytes increased more than 4-fold during development, and at 120 days cells of this type had 1.4-fold the specific activity of forebrain homogenates. The G6PDH activities in oligodendrocytes from 10-day-old rats were 1.4-fold the activities in the forebrain homogenates. The activities of this enzyme in oligodendrocytes were progressively lower at later ages, such that at 120 days the cells had 0.8 times the specific activities of homogenates. The oligodendrocytes had 0.6 times the homogenate activities of LDH at 10 days, and this ratio had decreased to 0.2 by 120 days. These enzymes were also measured in myelin isolated from 20-, 60-, and 120-day-old rats. By 120 days the specific activities of G6PDH and LDH in myelin were less than 8% of the respective activities in homogenates. The GPDH activity in myelin was, however, at least 20% the specific activity in the homogenates, even in the oldest animals. It is proposed that LDH could be used as a marker for oligodendroglial cytoplasm in subfractions of myelin and in myelin-related membrane vesicles.

Animals↗
PubMed1999

Structure and mechanism of soluble quinoprotein glucose dehydrogenase.

Soluble glucose dehydrogenase (s-GDH; EC 1.1.99.17) is a classical quinoprotein which requires the cofactor pyrroloquinoline quinone (PQQ) to oxidize glucose to gluconolactone. The reaction mechanism of PQQ-dependent enzymes has remained controversial due to the absence of comprehensive structural data. We have determined the X-ray structure of s-GDH with the cofactor at 2.2 A resolution, and of a complex with reduced PQQ and glucose at 1.9 A resolution. These structures reveal the active site of s-GDH, and show for the first time how a functionally bound substrate interacts with the cofactor in a PQQ-dependent enzyme. Twenty years after the discovery of PQQ, our results finally provide conclusive evidence for a reaction mechanism comprising general base-catalyzed hydride transfer, rather than the generally accepted covalent addition-elimination mechanism. Thus, PQQ-dependent enzymes use a mechanism similar to that of nicotinamide- and flavin-dependent oxidoreductases.

Binding Sites↗
PubMed1991

Glucose dehydrogenase from Bacillus subtilis expressed in Escherichia coli. I: Purification, characterization and comparison with glucose dehydrogenase from Bacillus megaterium.

Escherichia coli containing the Bacillus subtilis glucose dehydrogenase gene on a plasmid (prL7) was used to produce the enzyme in high quantities. Gluc-DH-S was purified from the cell extract by (NH4)2SO4-precipitation, ion-exchange chromatography and Triazine-dye chromatography to a specific activity of 375 U/mg. The enzyme was apparently homogenous on SDS-PAGE with a subunit molecular mass of 31.5 kDa. Investigation of Gluc-DH-S was performed for comparison with the corresponding properties of Gluc-DH-M. The limiting Michaelis constant at pH 8.0 for NAD+ is Ka = 0.11 mM and for D-glucose Kb = 8.7 mM. The dissociation constant for NAD+ is Kia = 17.1 mM. Similar to Gluc-DH-M, Gluc-DH-S is inactivated by dissociation under weak alkaline conditions at pH 9.0. Complete reactivation is attained by readjustment to pH 6.5. Ultraviolet absorption, fluorescence and CD-spectra of native Gluc-DH-S, as well as fluorescence- and CD-backbone-spectra of the dissociated enzyme were nearly identical to the corresponding spectra of Gluc-DH-M. The aromatic CD-spectrum of dissociated Gluc-DH-S was different, representing a residual ellipticity of tryptophyl moieties in the 290-310 nm region. Density gradient centrifugation proved that this behaviour is due to the formation of inactive dimers in equilibrium with monomers after dissociation. In comparison to Gluc-DH-M, the kinetics of inactivation as well as the time-dependent change of fluorescence intensity at pH 9.0 of Gluc-DH-S showed a higher velocity and a changed course of the dissociation process.

Bacillus megaterium↗
PubMed1975

Activity of some enzymes of carbohydrate metabolism in human subcutaneous adipose tissue in newborns, infants and adults. I. Activity of pyruvate kinase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase.

The activity of glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, pyruvate kinase (PK) and lactate dehydrogenase (LDH) was measured in human adipose tissue (AT) of newborns aged 0-2 and 2-48 h, of 3- to 5-month-old infants and of adults. AT was sampled by means of a special needle from the gluteal region without anesthesia. We observed significantly higher activity of the two pentose phosphate shunt enzymes when calculated on protein content and wet weight basis in newborns as compared to infants and adults. There were no differences for PK and LDH between newborns and adults when the values were calculated for the soluble protein. The protein concentration of the AT decreased significantly during the development.

Adipose Tissue↗
PubMed1982

Glycerolphosphate dehydrogenase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase and carbonic anhydrase activities in oligodendrocytes and myelin: comparisons between species and CNS regions.

Oligodendrocytes isolated from bovine white matter had higher specific activities of glycerolphosphate dehydrogenase (GPDH) and glucose-6-phosphate dehydrogenase (G6PDH) than were observed in homogenates of white matter or gray matter from bovine brains, whereas the activity of lactate dehydrogenase (LDH) was lower in the cells than in the homogenates. These observations suggest that G6PDH, as well as GPDH, is an oligodendrocyte-enriched enzyme. The 3 enzymes were also measured in myelin from bovine brains, rat spinal cords, and mouse brains, and, for each enzyme, the relative specific activity (RSA) in myelin was calculated by dividing the specific activity in myelin by the specific activity in the respective starting homogenate. Of the 3 enzymes, GPDH, G6PDH and LDH, the RSA of G6PDH was highest, at 0.26, in the bovine myelin, whereas the RSAs of GPDH were highest, at approximately 0.20, in the myelin from rat spinal cords and mouse brains. Carbonic anhydrase was also measured in the myelin from the rodent tissues, and significantly higher RSAs, at 0.43-1.06, were obtained. The finding that carbonic anhydrase consistently has higher concentrations than either G6PDH or GPDH in myelin suggests that the latter are restricted, in the myelin sheath, to regions in which oligodendroglial cytoplasm is enclosed, whereas carbonic anhydrase is distributed more broadly in the myelin membranes. A developmental increase in GPDH in the rat spinal cord is also reported.

Aging↗