Reversible Oxidation of Glucose by Glucose Dehydrogenase

Strecker, Harold J.; Korkes, Seymour

doi:10.1038/168913b0

Cited by 28 publications

(18 citation statements)

References 6 publications

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“…The specificity for the p-anomer is the same as for the NAD' -dependent glucose dehydrogenase [15] and as expected for the transfer of a hydride ion from glucose to a pyridine nucleotide [16]. The half-life for mutarotation of about 45 min in our experiments is consistent with the rate constant of 0.026 min-' (half-life = 27 min) determined by Grimshaw [17] at pH 7.0 and 25 "C.…”

Section: The Glucose/gluconolactone Halflreactionsupporting

confidence: 79%

The kinetics of glucose–fructose oxidoreductase from Zymomonas mobilis

Hardman

Scopes

1988

European Journal of Biochemistry

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1. Glucose -fructose oxidoreductase operates by a classic ping-pong mechanism with a single site for all substrates: glucose, fructose, gluconolactone and sorbitol. The K , values for these substrates were determined. The values of k,,, are 200 s-' and 0.8 s-' for the forward and reverse directions respectively.2. The overall catalytic process consists of two half-reactions with alternate reduction of NADP' and oxidation of NADPH tightly bound to the enzyme. Reduction of enzyme-NADP' by glucose and oxidation of enzyme-NADPH by gluconolactone involve single first-order processes. The values of the rate constants at saturating substrate are 2100 s-l and 8 s-' respectively; deuterium isotope effects indicate that these are for the hydrogen transfer step. Oxidation of enzyme-NADPH by fructose is first order with a limiting rate constant of at least 430 s-'. The reaction of enzyme-NADP' with sorbitol is biphasic, with rate constants for both phases less than 1 s-', This behaviour is explained by a mechanism in which the slow cyclisation of the acyclic form of fructose follows its dissociation from the enzyme.3. The rate-determining steps for the overall reaction are probably dissociation of gluconolactone in the forward direction and hydrogen transfer from sorbitol to enzyme-bound NADP' in the reverse direction.Following the discovery that the ethanol-producing bacterium Zymomonas mobilis produced sorbitol as well as ethanol when grown on sucrose or glucose/fructose mixtures [l -31, an enzyme was identified which catalysed the process [4, 51. The purified enzyme contains tightly bound NADP' and transfers hydrogens from glucose to fructose, producing gluconod-lactone and sorbitol [ 5 ] . The enzyme, named glucose -fructose oxidoreductase, is present in amounts up to 0.7% of the cytoplasmic protein; it was found to have low affinity for its substrates, but a high specific activity [ 5 ] . The presence of a gluconolactonase in Z . mobilis [5] ensures that the reaction is not reversible in vivo; thus the enzyme does not provide a route for metabolising sorbitol.Preliminary kinetic studies on the enzyme showed that the mechanism is ping pong, with a reduced NADP-enzyme intermediate. The K, for glucose was estimated to be between 6 -30 mM [4,5], highly dependent on fructose concentration, and the K , for fructose may be greater than 1 M.The ability to isolate the enzyme in large quantities, and a simple detection system for the reduced enzyme intermediate, have allowed us to carry out stopped-flow studies of the half-reactions and characterise the principal rate constants. A simple assay system for the reverse reaction has enabled us to obtain a detailed picture of the kinetic behaviour of the enzyme at pH 6.5. MATERIALS AND METHODSD-Glucose (predominantly a) was AR grade from Ajax Chemicals (Sydney, Australia). To ensure equilibration of the CI and B forms of D-glucose, stock glucose solutions were made up at least 18 h before use, unless otherwise stated below. Fructose (containing < 0.05% glucose), B-D-glucose (contain...

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Section: The Glucose/gluconolactone Halflreactionsupporting

confidence: 79%

The kinetics of glucose–fructose oxidoreductase from Zymomonas mobilis

Hardman

Scopes

1988

European Journal of Biochemistry

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“…This includes our first enzyme, GDH, the mechanism of action of which is relatively standard, [84][85][86] The output product, NADH, denoted P for brevity, once it is generated by the GDH process, activates all the "direct" complex-formation and redox conversions involving MDH. As a result, not only is NADH partially converted back to NAD + , to be denoted N, but also the concentration of malate, denoted M, builds up.…”

Section: A Model For the Mdh Kinetics With Inhibitionmentioning

confidence: 99%

Kinetic Model for a Threshold Filter in an Enzymatic System for Bioanalytical and Biocomputing Applications

Privman¹,

Domanskyi²,

Mailloux³

et al. 2014

J. Phys. Chem. B

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A recently experimentally observed biochemical "threshold filtering" mechanism by processes catalyzed by the enzyme malate dehydrogenase is explained in terms of a model that incorporates an unusual mechanism of inhibition of this enzyme that has a reversible mechanism of action. Experimental data for a system in which the output signal is produced by biocatalytic processes of the enzyme glucose dehydrogenase are analyzed to verify the model's validity. We also establish that fast reversible conversion of the output product to another compound, without the additional inhibition, cannot on its own result in filtering.

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“…The formation of three r-pyrone derivatives from 2,5-diketogluconate was also proved with intact cells. Therefore the three r-pyrone derivatives were assumed to be formed via direct oxidative pathway as shown in the next page, From analogy with the oxidation of glucose by notatin l3 ) or by an ox-liver 14 ) preparation, where gluconic acid lactone is the primary product, and the similar oxidation of glucose-6-phosphate to 6-phosphogluconolactone 15J , it is tempting to postulate that the first stage may be the removal of two hydrogen atoms from carbon atom I of' glucopyranose. Such oxidations, i,e.…”

Section: Discussionmentioning

confidence: 99%

Studies on Oxidative Fermentation

Aida

Fujii

Asai

1957

Bulletin of the Agricultural Chemical Society of Japan

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The three r-pyrone derivatives, i.e. comenic acid, rubiginic acid and rubiginol were confirmed to be formed from glucose via gluconate, 2-ketogluconate and 2,5-diketogluconate by Gluconoacetobacter lig.. Other organic acids. such as glycolic and tartronic acids were also formed from glucose via 2.5-diketogluconate. Thus, the presumable pathway of glucose degradation to the three r-pyrone derivatives is proposed here.

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Reversible Oxidation of Glucose by Glucose Dehydrogenase

Cited by 28 publications

References 6 publications

The kinetics of glucose–fructose oxidoreductase from Zymomonas mobilis

The kinetics of glucose–fructose oxidoreductase from Zymomonas mobilis

Kinetic Model for a Threshold Filter in an Enzymatic System for Bioanalytical and Biocomputing Applications

Studies on Oxidative Fermentation

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