Glucose oxidation reaction

During normal activity, a person uses the equivalent of about 10 MJ of energy a day. Assume that this value represents AG, and estimate the average current through your body in the course of a day, assuming that all the energy that we use arises from the reduction of 02 in the glucose oxidation reaction. See Box 12.1. 

Figure 4. Catalytic activity of the Au/C large-scale preparations and the 2g preparation in glucose oxidation. Reaction conditions glucose 50wt.% S/M ratio 20,000 O2 flow INL/min stirring rate 1700rpm. pH 9.5.

The glucose oxidation reaction in the enzyme immobilized membrane of the glucose sensors is performed according to the following reaction. 

Nikov I, Paev K. Palladium on alumina catalyst for glucose oxidation reaction kinetics and catalyst deactivation. Catal. Today 1995f24 41-47. 

In summation, three pentose molecules (3X5 = 15C) produce two hexoses and one triose (2X6-1-1X3 = 15C). The hexoses can reenter the direct glucose oxidation reaction (fructose-6-P must first be isomerized to glucose-6-P). 

FIGURE 14.1 Reaction profile showing large AG for glucose oxidation, free energy change of —2,870 kj/mol catalysts lower AG, thereby accelerating rate. 

Elucidation of the glycolysis process (by G. Embden and by O. Meyerhof) followed by the glucose oxidation process (H. A. Krebs. 1937) established the intimate involvement of P compounds in miiny biochemical reactions. 

ATP synthase reaction has been calculated as approximately 51.6 kJ. It follows that the total energy captured in ATP per mole of glucose oxidized is 1961 kJ, or approximately 68% of the energy of combustion. Most of the ATP is formed by oxidative phosphorylation resulting from the reoxidation of reduced coenzymes by the respiratory chain. The remainder is formed by substrate-level phosphorylation (Table 17—1). 

A reaction of practical importance is the oxidation of a carbohydrate aldehyde group to a carboxyl group. This is the basis for a process converting glucose to calcium gluconate, a substance of pharmaceutical interest. The oxidation reaction occurs at graphite electrodes in the presence of the Brj/Br" redox system. Calcium salt is added to the solution to prevent further oxidation of free gluconic acid. 

An example of an oxidation reaction is the production of citric acid from glucose ... 

The first enzyme biosensor was a glucose sensor reported by Clark in 1962 [194], This biosensor measured the product of glucose oxidation by GOD using an electrode which was a remarkable achievement even though the enzyme was not immobilized on the electrode. Updark and Hicks have developed an improved enzyme sensor using enzyme immobilization [194], The sensor combined the membrane-immobilized GOD with an oxygen electrode, and oxygen measurements were carried out before and after the enzyme reaction. Their report showed the importance of biomaterial immobilization to enhance the stability of a biosensor. 

One of the best known enzymatic reactions involving glucose is the following oxidation reaction catalysed by glucose oxidase (GOD) ... 

Figure 6.1 Pathways involved in glucose oxidation by plant cells (a) glycolysis, (b) Krebs cycle, (c) mitochondrial cytochrome chain. Under anoxic conditions. Reactions 1, 2 and 3 of glycolysis are catalysed by lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase, respectively. ATP and ADP, adenosine tri- and diphosphate NAD and NADHa, oxidized and reduced forms of nicotinamide adenine dinucleotide PGA, phosphoglyceraldehyde PEP, phosphoenolpyruvate Acetyl-CoA, acetyl coenzyme A FP, flavoprotein cyt, cytochrome e, electron. (Modified from Fitter and Hay, 2002). Reprinted with permission from Elsevier...

The oxidation reactions of luminol and lucigenin can be used to assay for H Oj. For example, analysis of glucose in biological systems can be achieved using a three-enzyme system of mutarotase, glucose oxidase and horseradish peroxidase by correlation with the amount of HjOj released. Similarly, cholesterol can be measured using cholesterol oxidase. The fact that the rate of luminol oxidation depends on the concentration of the catalyst can be used as a method for determination of Co +, Fe +, Cr + and Mn + and other catalysts.Some examples of the use of luminol, isolumi-nol and their derivatives in immunoassays are shown in Table 3.11. ... 

Another technique used is a cyclic voltammetry (CV) in the presence of electron mediator. In the GOx-catalyzed oxidation reaction of glucose, cofactor FAD, which is contained at the active center of GOx, oxidizes glucose to gluconolactone and resultant FADHj is converted back to the active FAD form by Oj. In the conventional type of enzyme sensors, the H2O2 generated from O2 is oxidized at the electrode surface. 

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