Mathematical simulation of an amperometric enzyme-substrate electrode with a pO2 basic sensor. Part 2. Mathematical simulation of the glucose oxidase glucose electrode.
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Electrodes↗
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Results for “GLUCOSE OXIDASE”
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Monoclonal glucose-oxidase-anti-glucose-oxidase (GAG) immunosandwich assay for the detection of monoclonal antibodies on routine hematological smears.
A murine monoclonal antibody specific for aspergillus niger glucose oxidase has been prepared and used in an unlabeled antibody bridge technique for the detection of monoclonal antibodies. This procedure--the monoclonal glucose oxidase anti-glucose oxidase (GAG) immunosandwich assay--provides excellent immunocytochemical labeling of routine hematological films in combination with optimal preservation of cellular details. In contrast to conventional immunofluorescence procedures, routine hematological films can be used, and these can be stored before and after the immunolabeling. Compared with other immunoenzyme techniques such as those using alkaline phosphatase or peroxidase, the GAG assay is as sensitive and has the advantage that no problems with endogenous enzyme activity are encountered. The availability of alcohol-resistant disclosing reagents allows for routine hematological counterstaining which provides a very clear visualization of both the immunoreaction and the individual morphology of the blood cells.
Antibodies, Monoclonal↗
A study on the thermostability of microencapsulated glucose oxidase.
Glucose oxidase was microencapsulated within polyurea membranes by the interfacial polymerization method and the stability to heat of the encapsulated enzyme was examined. Thermostability of microencapsulated glucose oxidase was prominent and increased with increase in the amount of glucose oxidase entrapped. This stability, however, could not be ascribed to the peculiar properties of microcapsules but was suggested to be caused by the incorporation of glucose oxidase molecules in the membranes through chemical bonding. This stability revealed that the enzyme molecules in the microcapsules could not always exist in the dissolved form but a fairly large portion of the molecules participated in the polymerization reaction and changed their enzymatic properties.
Drug Compounding↗
Antibacterial effect of the glucose oxidase-glucose system on food-poisoning organisms.
The antibacterial effect of the glucose oxidase-glucose system was studied on food-poisoning organisms including Staphylococcus aureus, Salmonella infantis, Clostridium perfringens, Bacillus cereus, Campylobacter jejuni, Listeria monocytogenes and Yersinia enterocolitica using automated turbidometry. The bacteria were grown in sterile-filtered meat medium which was either raw or heat-denaturated. The results showed a clear growth inhibition with combinations of 0.5-1.0 mg/ml glucose and 0.5-1.0 IU/ml glucose oxidase. The growth inhibition was more effective in the heat-denaturated meat medium. The most resistant pathogens were Campylobacter jejuni and Listeria monocytogenes, however growth inhibition was still evident. The possible application of the glucose oxidase-glucose system in food products inhibiting the growth of pathogens and spoilage organisms is discussed.
Animals↗
Determination of a large reorganization energy barrier for hydride abstraction by glucose oxidase.
Glucose oxidase mediates the aerobic oxidation of simple sugars to lactones using a noncovalently bound flavin cofactor. The chemical mechanism of this reaction has been uncertain for many years. Here it is shown, using enzymes reconstituted with chemically modified cofactors, that sugar oxidation most likely occurs by concerted hydride (H-) abstraction. Studies of the kinetics and thermodynamics together with the application of Marcus theory reveal a large reorganization energy barrier. The magnitude of this intrinsic contribution appears characteristic of H- transfer in proteins and in solution. The observation that neither the thermodynamics nor reorganization energy is significantly altered in the glucose oxidase active site raises questions concerning how the redox reaction may be catalyzed.
Glucose Oxidase↗
A theoretical study of the dioxygen activation by glucose oxidase and copper amine oxidase.
Glucose oxidase (GO) and copper amine oxidase (CAO) catalyze the reduction of molecular oxygen to hydrogen peroxide. If a closed-shell cofactor (like FADH(2) in GO and topaquinone (TPQ) in CAO) is electron donor in dioxygen reduction, the formation of a closed-shell species (H(2)O(2)) is a spin forbidden process. Both in GO and CAO, formation of a superoxide ion that leads to the creation of a radical pair is experimentally suggested to be the rate-limiting step in the dioxygen reduction process. The present density functional theory (DFT) studies suggest that in GO, the creation of the radical pair induces a spin transition by spin orbit coupling (SOC) in O(2)(-)(rad), whereas in CAO, it is induced by exchange interaction with the paramagnetic metal ion (Cu(II)). In the rate-limiting step, this spin-transition is suggested to transform the O(2)(-)(rad)-FADH(2)(+)(rad) radical pair in GO and the Cu(II)-TPQ (triplet) species in CAO, from a triplet (T) to a singlet (S) state. For CAO, a mechanism for the O[bond]O cleavage step in the biogenesis of TPQ is also suggested.
Amine Oxidase (Copper-Containing)↗
Characterization of thin layers of glucose oxidase.
Glucose Oxidase (GOD) has been covalently bound to functionalized glass cover slips. The surface density of immobilized GOD molecules was measured by a method based on the amperometric determination of Flavin Adenine Dinucleotide (FAD). Atomic Force Microscopy (AFM) images, obtained in aqueous solution for the covalently bound enzyme, show a monomolecular layer of the enzyme on a functionalized glass surface. The catalytic constants were measured for the immobilized GOD and compared with those of the free enzyme.
Glass↗
Reactivity and stability improvement of immobilized glucose oxidase.
Glucose oxidase (GOD) was immobilized on agrose(a) by diazotization using p(beta-sulfate-ethylfonyl)aniline(SESA) as cross-linking agent, (b) by a new improved glutaraldehyde method and (c) by polyacrylamide entrapment. Results showed that GOD immobilized by the improved glutaraldehyde method had an activity of 10% and 100% higher than that by diazotization and entrapment method respectively. Catalase co-immobilized with GOD on agrose greatly enhanced the stability of GOD. Proteins such as hemoglobin(Hb), bovine serum albumin(BSA) and reducing agent i.e. VitC added during immobilization had the same effect but to a lesser extent.
Drug Stability↗
[Preparation and properties of immobilized glucose oxidase].
Glucose oxidase from Penicillium notatum was immobilized by covalent, adsorptive or ion exchange attachment to insoluble carriers. The yields of immobilization using Spherons, DEAE-Sephadex, DEAE-cellulose and porous glass carriers are compared. Methods used for the estimation of kinetic parameters Km and kcat are described and results obtained for GOD in solution and in immobilized form are given. Investigations about the dependence of the enzymatic activity on pH, temperature and storage serve for the further characterization of the GOD-derivatives. There are no significant changes in the functional behaviour of the enzyme due to immobilization on selected carriers. The results are discussed with regard to application of carrier bound GOD in enzyme reactors.
Drug Stability↗
Reversible denaturation behavior of immobilized glucose oxidase.
Glucose oxidase (GOD) was immobilized by using glutaraldehyde crosslinking and various stabilizing agents such as BSA, gelatin, lysozyme, and polyethylenimine (PEI). Studies on the denaturation of the soluble as well as immobilized GOD were carried out for 1 h at various concentrations of guanidine hydrochloride (GdmCl) in 50 mM phosphate buffer, pH 6.0 at 25 +/- 1 degrees C. The soluble enzyme required a GdmCl concentration of 5 M for total activity loss, whereas for GOD immobilized with BSA, gelatin, lysozyme, and heat-inactivated lysozyme, the corresponding GdmCl concentration required was 8 M. GOD immobilized with PEI, however, was more stable and retained 25% activity when denatured for 1 h using 8 M GdmCl. However, after undergoing denaturation for 1 h, GOD immobilized with lysozyme regained 72% original activity within 20 min of renaturation, while GOD immobilized with BSA, PEI, gelatin, and heat-inactivated lysozyme regained only 39, 21, 20, and 25% of activity, respectively. After five cycles of repeated denaturation and renaturation with 8 M GdmCl, GOD immobilized with lysozyme retained 70% of the original activity. Refolding ability of lysozyme, glutaraldehyde crosslinkages between lysozyme and GOD, together with ionic interactions between them, appear to play an important role in the denaturation-renaturation behavior of the immobilized enzyme.
Buffers↗
Multilayer membranes via layer-by-layer deposition of organic polymer protected Prussian blue nanoparticles and glucose oxidase for glucose biosensing.
Polyelectrolyte multilayers (PEMs) are now widely used for bioanalytical applications. In this work, a bilayer of poly(diallydimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS) is consecutively adsorbed on 3-mercapto-1-propanesulfonic acid modified Au electrode surfaces, forming stable, ultrathin multilayer films. Subsequently, Prussian blue nanoparticles protected by PDDA (denoted as P-PB) and negatively charged glucose oxidase (GOx) are consecutively adsorbed onto the PSS-terminated bilayer. The growth of each of the P-PB/GOx bilayers is followed quantitatively using UV-visible absorption spectroscopy and the electrochemical method. The P-PB nanoparticles can catalyze the electroreduction of hydrogen peroxide formed from enzymatic reaction at lower potential and inhibit the responses of interferents, such as ascorbic acid (AA) and uric acid (UA). Performance of the multilayer films can be tailored by controlling the number of bilayers. Under optimal conditions, a linear range of 0.10 to 11.0 mM and a detection limit of 10 microM were achieved. The glucose biosensor has good stability and reproducibility.
Biosensing Techniques↗
The direct electron transfer of glucose oxidase and glucose biosensor based on carbon nanotubes/chitosan matrix.
The glucose oxidase (GOD) is entrapped in the composite of carbon nanotubes/chitosan and direct electron transfer reaction between GOD and electrode takes place. The electron transfer rate of GOD is greatly enhanced to 7.73 s(-1) in the system, which is more than one-fold higher than that of flavin adenine dinucleotide adsorbed on the carbon nanotubes (3.1 s(-1)). This maybe results from the conformational change of GOD in the microenvironment enabling the accessibility of active site for GOD to the electrode. Additionally, the bioactivity of GOD modified in the composite on electrode surface is kept. So as-prepared electrode can be used as a glucose biosensor exhibiting higher sensitivity (0.5 microA mM(-1)) and better stability. The facile procedure of immobilizing GOD will promote the developments of electrochemical research for protein, biosensors and other bioelectrochemical devices.
Adsorption↗
Widespread occurrence of galactose oxidase and glucose oxidase in fungi.
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Alcohol Oxidoreductases↗
[Study on starting enzymes in glucose determination--glucose oxidase, hexokinase, glucose dehydrogenase (author's transl)].
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Blood Glucose↗
Covalently bound phosphate residues in bovine milk xanthine oxidase and in glucose oxidase from Aspergillus niger: a reevaluation.
The reported presence of covalently bound phosphate residues in flavoproteins has significant implications with regard to the catalytic mechanisms and structural stability of the specific enzymes themselves and in terms of general cellular metabolic regulation. These considerations have led to a reevaluation of the presence of covalently bound phosphorus in the flavoproteins xanthine oxidase (xanthine: oxygen oxidoreductase, EC 1.1.3.22) and glucose oxidase (beta-D-glucose: oxygen 1-oxidoreductase, EC 1.1.3.4). Milk xanthine oxidase purified by a procedure that includes anion-exchange chromatography is shown to contain three phosphate residues. All three are noncovalently associated with the protein, two with the FAD cofactor, and one with the molybdenum cofactor. Results of chemical analysis and 31P NMR spectroscopy indicate that enzyme purified by this method contains no phosphoserine residues. Xanthine oxidase preparations purified by chromatography on calcium phosphate gel in place of DEAE-Sephadex yielded higher phosphate-to-protein ratios, which could be reduced to the expected values by additional purification on a folate affinity column. Highly active, highly purified preparations of glucose oxidase are shown to contain only the two phosphate residues of the FAD cofactor. The covalently bound bridging phosphate reported by others may arise in aged or degraded preparations of the enzyme but appears not to be a constituent of functional glucose oxidase. These results suggest that the presence of covalent phosphate residues in other flavoproteins should be rigorously reevaluated as well.
Animals↗
Improving accuracy of glucose oxidase procedure for glucose determinations on discrete analyzers.
We describe a rapid kinetic glucose oxidase (EC 1.1.3.4) procedure for quantifying glucose. Glucose oxidase concentration was reduced from the more usual 20 kU/L to 4 kU/L, and pH was reduced from 7.0 to 6.6. Potassium ferrocyanide (20 mumol/L) and ascorbate oxidase (1 kU/L) were incorporated in the procedure. The assay results vary linearly with glucose concentration from 0 to 50 mmol/L and are unaffected by bilirubin concentrations less than or equal to 600 mumol/L, hemoglobin less than or equal to 12 g/L, Intralipid less than or equal to 4 g/L, urate less than or equal to 1 mmol/L, and ascorbate less than or equal to 2.0 mmol/L. The assay is readily adaptable to most open-system analyzers.
Ascorbic Acid↗
BIOCHEMISTRY OF GLUCOSE OXIDASE. I. METHEMOGLOBIN FORMATION AFTER GLUCOSE OXIDASE INJECTION IN MICE. ANL-6723.
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Biochemistry↗
Comparison of the glucose oxidase method for glucose determination by manual assay and automated analyzer.
In experimental models of diabetes, glucose levels in plasma and blood are commonly determined by colorimetric assay and by automated analyzers based on the glucose oxidase conversion of glucose and O2 to gluconate and H2O2. We have compared the glucose levels obtained by these two methods in control Wistar rats, streptozotocin diabetic Wistar rats, Zucker fa/fa fatty rats and Zucker Diabetic Fatty rats. We found that the manual glucose assay and the glucose analyzer produced comparable values up to concentrations of about 25 mM. Above this level, samples should be diluted.
Animals↗