Glucose oxidase -catalyzed reduction

The direct incomplete oxidation of sugars without phosphorylation leads to the formation of the corresponding ketones. The aldoses are oxidized into aldonic acids. The aldehydic function of this sugar is transformed into a carboxylic acid function. Glucose is oxidized into gluconic acid in this manner. The glucose oxidase catalyzes the reaction, which is coupled with the reduction of FAD. In acetic acid bacteria, electrons and protons are transported by the cytochrome chain to oxygen, which is the final acceptor. 

Sensors have also been constructed from some oxidases directly contacted to electrodes to give bioelectrocatalytic systems. These enzymes utilize molecular oxygen as the electron acceptor for the oxidation of their substrates. Enzymes such as catechol oxidase, amino acid oxidase, glucose oxidase, lactate oxidase, pyruvate oxidase, alcohol oxidase, xanthine oxidase and cholesterol oxidase catalyze the oxidation of their respective substrates with the concomitant reduction of O2 to H2O2 ... 

Hydrogen peroxide is produced industrially by (1) the base/anthraquinone-catalyzed chemical reduction of O2 by water and (2) the palladium-catalyzed hydrogenation of O2. In aerobic biology many oxidases (dehydrogenases) produce HOOH as a biproduct along with oxidized substrate (e.g., glucose oxidase, O2 +... 

Glucose oxidase (GO) catalyzes the oxidation of sugars to their corresponding lactone products, coupled to the reduction of O2 to H2O2, Scheme 10.3. The reaction... 

Detailed studies of glucose oxidase immobilized in poly(N-methypyrrole) films using both ferrocene monocarboxylic acid and ferricyanide as the mediator species indicate that in both cases poly(N-methylpyrrole) films are insulating and there is no evidence of direct reoxidation of the mediator on the polymer. This is an unexpected result, since these mediators are electroactive at poly(N-methylpyrrole) films that do not contain GOx. It appears that in addition to catalyzing the oxidation of glucose in the presence of a mediator, GOx can also catalyze the reduction of oxygen to H2O2 in the presence of mediators (M) as electron acceptors... 

Figure 3-18 A two-electron HRC scheme the ferrocene carboxylic acid catalyzed reduction of glucose oxidase.

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