Reactivity glucose oxidase

Entrapment of biochemically reactive molecules into conductive polymer substrates is being used to develop electrochemical biosensors (212). This has proven especially useful for the incorporation of enzymes that retain their specific chemical reactivity. Electropolymerization of pyrrole in an aqueous solution containing glucose oxidase (GO) leads to a polypyrrole in which the GO enzyme is co-deposited with the polymer. These polymer-entrapped GO electrodes have been used as glucose sensors. A direct relationship is seen between the electrode response and the glucose concentration in the solution which was analyzed with a typical measurement taking between 20 to 40 s. 

Figure 12.6 The immobilized glucose oxidase/lactoperoxidase system radioiodinates proteins through the intermediate formation of hydrogen peroxide from the oxidation of glucose. H2O2 then reacts with iodide anions to form reactive iodine (I2). This efficiently drives the formation of the highly reactive H2OI+ species that is capable of iodinating tyrosine or histidine residues (see Figure 12.2).

Other minor enzyme systems can be used such as betagalactosidase (5). This system works well however, it can lead to some false-positive problems resulting from endogenous enzymes that have a similar reactivity (d). Another enzyme not commonly used is glucose oxidase. A glucose oxidase system... 

The present volume is a non-thematic issue and includes seven contributions. The first chapter byAndreja Bakac presents a detailed account of the activation of dioxygen by transition metal complexes and the important role of atom transfer and free radical chemistry in aqueous solution. The second contribution comes from Jose Olabe, an expert in the field of pentacyanoferrate complexes, in which he describes the redox reactivity of coordinated ligands in such complexes. The third chapter deals with the activation of carbon dioxide and carbonato complexes as models for carbonic anhydrase, and comes from Anadi Dash and collaborators. This is followed by a contribution from Sasha Ryabov on the transition metal chemistry of glucose oxidase, horseradish peroxidase and related enzymes. In chapter five Alexandra Masarwa and Dan Meyerstein present a detailed report on the properties of transition metal complexes containing metal-carbon bonds in aqueous solution. Ivana Ivanovic and Katarina Andjelkovic describe the importance of hepta-coordination in complexes of 3d transition metals in the subsequent contribution. The final chapter by Sally Brooker and co-workers is devoted to the application of lanthanide complexes as luminescent biolabels, an exciting new area of development. 

Examples of this class of enzymes are glucose oxidase and D-amino acid oxidase The classification of the flavoproteins used here is that originally suggested which has been modified recently . In the author s own view the original classification has the advantage of being simple and yet quite useful whereas the new classification does not add to simplify and classify the rather complex picture of flavoprotein catalysis. Nevertheless, in flavoprotein oxidases, the 1,5-dihydroflavin is very reactive towards Oj. On the other hand, the two-electron reduced form of flavoprotein oxidases reacts slowly with pure one-electron acceptors, e.g. ferricyanide. That the two-electron transition is biologically favoured in these enzymes explains why they can react easily with sulfite... 

S108 Morris, D.L. (1985). Effect of antibodies to glucose oxidase in the apoenzyme reactivation immunoassay system. Anal. Biochem. ISl, 235-241. 

As stated above, SECM can be used to image the reactivity of surface features. A feedback detection scheme was used to observe the localized reaction of glucose oxidase and mitochondria-bound NADH-cytochrome c reductase (7). The spatial resolution of the imaging is high for enzymatic... 

Stankovich, M. T., Schopfer, L. M., Massey, V., Determination of Glucose Oxidase Oxidation-Reduction Potentials and the Oxygen Reactivity of Fully Reduced Semiquinoid Forms , J. Biol. Chem. 253 (1978) 4971-4979. 

There has been must less work directed to exploiting endogenous or targeted oxidative reactivity in tumours, compared to work on bioreductive drugs. Glucose oxidase or hypoxanthine/xanthine oxidase has been explored as sources of hydrogen peroxide or superoxide radicals [154,155], and the effects on tumour growth of ischaemia/reperfusion (which leads to a superoxide burst ) has been studied [156,157]. 

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