Glucose dehydrogenase , NADH

Figure 15-4. Example of reduction using glucose/glucose dehydrogenase NADH recycling system1261.

When glucose is oxidized by glucose dehydrogenase, NADH is simultaneoulsy formed, whose fluorescence can be detected via fiber optics [73]. This concept will be discussed in... 

Another type of sensor was based on the utilization of glucose dehydrogenase enzyme coupling with /ra(2,2 -bipyridylruthenium(II) complex [31]. This sensor can be used in the 10-2500-pmol/L concentration range. Several interferences occur, like NADH, oxalate, proline, and tripropylamine. However, gluconic acid and NAD+ do not interfere. 

Figure 9. Preparation of L- and D-lactaldehyde and L- and D-2-hydroxybutyraldehyde. HLADH, horse liver alcohol dehydrogenase (NADH was regenerated by glucose/glucose dehydrogenase).

Testicular effects were also investigated after oral administration of 2000 mg/kg bw di(2-ethylhexyl) phthalate for seven consecutive days to 13-week-old male Wistar rats (Saxena et al., 1985). Degeneration was observed in about 40% of the seminiferous tubules. Loss of succinic dehydrogenase, NADH-diaphorase and acid phosphatase activity and increases in adenosine triphosphatase, glucose-6-phosphate dehydrogenase and alkaline phosphatase activity were observed in treated rats. 

The most convenient and useful enzymatic methods for the regeneration of NAD(P)H are formate/formate dehydrogenase for NADH [210, 211], iso-propanol/TBADH for NADPH [57], isopropanol/ADH (Pseudomonas sp.) for NADH [61, 212] and glucose/glucose dehydrogenase (Bacillus sp.) for NADH and NADPH [213],... 

For a restricted number of reactions the product formed will spontaneously and rapidly react with water, driving the reaction to the product side, thus favoring NADH production. Examples of such systems are the enzymatic oxidation of aldoses e.g. the oxidation of j3-D-glucose with glucose dehydrogenase (GDH). In a first reversible reaction the aldose is oxidized to form a lactone ... 

A. glucose-6-phosphate dehydrogenase, NADH, gluconolactone hydrolase, 6-phosphogluconate dehydrogenase, ribulose-5-phosphate epimerase... 

An analogous amplification process for determination of phenols was proposed based on the kinetics of disappearance of /1-NADH reacting with quinone, which is derived from a phenol in a tyrosinase-catalyzed oxidation. LOD was as low as 50 nM in a 10 min assay . Amplification cycles were also achieved by combining a Pt electrode where phenols are oxidized with a polyurethane layer embedding pyrroloquinoline quinone-dependent glucose dehydrogenase, to catalyze the reduction of the oxidation products . 

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