Aerobic Oxidation of Glucose

Thielecke et al. have recently developed a flow reactor system for glucose oxidation by using AU/AI2O3 and Au/Ti02 as catalysts and have examined the long-term stability of the catalysts for industrial use [195-197]. The productivity of sodium gluconate was estimated to be 4.2 tg u and AU/AI2O3 showed no loss in catalytic activity and selectivity after 70 days operation [195]. 

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TAs one might predict, mutations in the genes for the subunits of the PDH complex, or a dietaiy thiamine deficiency, can have severe consequences. Thiamine-deficient animals are unable to oxidize pyruvate normally. This is of particular importance to the brain, which usually obtains all its energy from the aerobic oxidation of glucose in a pathway that necessarily includes the oxidation of pyruvate. Beriberi, a disease that results from thiamine deficiency, is characterized by loss of neural function. This disease occurs primarily in populations that rely on a diet consisting mainly of white (polished) rice, which lacks the hulls in which most of the thiamine of rice is found. People who habitually consume large amounts of alcohol can also develop thiamine deficiency, because much of their dietaiy intake consists of the vitamin-free empty calories of distilled spirits. An elevated level of pyruvate in the blood is often an indicator of defects in pyruvate oxidation due to one of these causes. ... 

TABLE 16-1 Stoichiometry of Coenzyme Reduction and ATP Formation in the Aerobic Oxidation of Glucose via Glycolysis, the Pyruvate Dehydrogenase Complex Reaction, the Citric Acid Cycle, and Oxidative Phosphorylation... 

The GOX-B-immunosensors are potentiostated at +0.6 V vs. SCE to detect the aerobic oxidation of glucose with the concomitant production of H202. 

Table 9.3 Calculation of ATP yields upon complete Aerobic oxidation of Glucose.

The aerobic oxidation of glucose yields between 29.5 and 31 ATP molecules. 

Enzymes are often employed in the chemical layer to impart the selectivity needed. We saw an example of this in Chapter 13 when discussing potentiometric enzyme electrodes. An example of an amperometric enzyme electrode is the glucose electrode, illustrated in Figure 15.4. The enzyme glucose oxidase is immobilized in a gel (e.g., acrylamide) and coated on the surface of a platinum wire cathode. The gel also contains a chloride salt and makes contact with silver-silver chloride ring to complete the electrochemical cell. Glucose oxidase enzyme catalyzes the aerobic oxidation of glucose as follows ... 

The reaction rate will be at a maximum at a certain pH, owing to complex acid-base equilibria such as acid dissociation between the substrate, the activated complex, and the products. Also, the maximum rate may depend on the ionic strength and on the type of buffer used. For example, the rate of aerobic oxidation of glucose in the presence of the enzyme glucose oxidase is maximum in an acetate buffer at pH 5.1, but in a phosphate buffer of the same pH, it is decreased. 

Mild to moderate-intensity exercise can be performed for longer periods than can high-intensity exercise. This is because of the aerobic oxidation of glucose and fatty acids, which generates more energy per fuel molecule than anaerobic metabolism, and which also produces acid at a slower rate than anaerobic metabolism. Thus, during mild and moderate-intensity exercise, the release of lactate diminishes as the aerobic metabolism of glucose and fatty acids becomes predominant. 

Recall the classic equation for the aerobic oxidation of glucose ... 

The analytical data show that gold catalysis and enzymatic catalysis allow fast and selective aerobic oxidation of glucose according to the same stoichiometry characterized by the formation of hydrogen peroxide as the by-product (Eq. (21.1)) [8]. However, it is not surprising that completely different catalytic systems adopt different reaction mechanisms as shown by the kinetic studies on commercial enzymatic preparations containing /wcose oxidase and catalase [13]. The results of the research support a Michaelis-Menten type mechanism where the kinetic... 

For industrial applications, metal catalysts should be repeatedly recycled or used in continuous mode for a long time. The introduction of gold catalysis in the aerobic oxidation of glucose has opened exciting perspectives Au is a biocompatible, nontoxic metal, which allows even superior productivities with respect to enzymatic catalysis [38], and no leaching problems have been observed using nanometric particles dispersed on different supports [43]. Compared with chemical oxidations, enzymatic catalysis suffers from more plant complexities... 

However, as the discussed aerobic oxidation of glucose teaches, a deep investigation on different alternatives must be performed, and the choice should be made after a critical comparison until few decades ago, noble metal catalysis was scarcely considered due to the cost of the catalyst and many prejudices. 

Scheme 12.15 Selective aerobic oxidation of glucose to gluconate catalysed by activated carbon supported gold nanoparticles in basic aqueous medium.

Fig. 13.4 Nanometric particles of different metals as catalysts for the aerobic oxidation of glucose. [Metal]=10 M, [Glucose]=0.4M, T=30°C, p02=l bar, pH=9.5.

Table 13.15 Aerobic oxidation of glucose with monometallic and bimetallic catalysts. Glucose/Au = 3000, T=70°C, p02 = 3 bar, t=6.5h.

This production of ATP from the complete aerobic catabolism of 1 mol of glucose in the liver is summarized in I Table 13.1. Notice from the table that of the 32 mol of ATP generated, the great majority (28 mol) is formed as a result of oxidative phosphorylation (last category in Table 13.1). In Section 13.4, we learned that only 2 mol of ATP is produced per mole of glucose by lactate fermentation and by alcoholic fermentation. Thus, in terms of ATP production from fuels, the complete aerobic oxidation of glucose is 16 times more efficient than either lactate or alcoholic fermentation. 

Filipin inhibited anaerobic and aerobic oxidation of glucose by S. cerevisiae but had no effect on the oxidative capacity of cell-free homogenates [141]. The antibiotic reduced the dry weight of the yeast with the loss of nitrogen and phosphorus from the cell. This was the first indication that the observed effects of polyenes on fungal metabolism were a consequence of altered cellular permeability and the fungicidal effect was the result of the loss of vital cytoplasmic components. 

Comotti M, Della Pina C, Falletta E, Rossi M (2006) Aerobic oxidation of glucose with gold catalyst hydrogen peroxide as intermediate and reagent. Adv Synth Catal 348(3) 313-316... 

Figure 16.1 Aerobic oxidation of glucose to generate 32 molecules of ATP.

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