Glucose dehydrogenase enzyme catalysts

Specific redox characteristics of a catalyst derived from CV scans are also used to confirm an enzyme s ability for bioelectrocatalysis by either direct electron transfer (DET) or mediated electron transfer (MET) to the electrode. DET and MET are two distinct mechanisms of bioelectrocatalysis. MET has the advantage of being compatible with almost all naturally occurring oxidoreductase enzymes and coenzymes, but it requires additional components (either smaU-molecule redox mediators or redox polymers) because the enzymes cannot efficiently transfer electrons to the electrode. These additional components make the system more complex and less stable [8]. The vast majority of oxidoreductase enzymes that require MET to an electrode are nicotinamide adenine dinucleotide (NAD" ) dependent. Two of the most commonly encountered NAD -dependent enzymes in BFC anodes are glucose dehydrogenase (GDH) and alcohol dehydrogenase (ADH). These enzymes have been thoroughly characterized in respect to half-cell electrochemistry and have been demonstrated for operation in BFC. More information about MET can be found in Chapter 9. 

The biochemist needs a test, called an assay, for some unique identifying property of the protein. A positive result on the assay indicates that the protein is present. Determining an effective assay is often difficult but, the more specific the assay, the more effective the purification. For enzymes, which are protein catalysts (Chapter 8), the assay usually measures enzyme activity—that is, the ability of the enzyme to promote a particular chemical reaction. This activity is often measured indirectly. Consider the enzyme lactate dehydrogenase, which catalyzes the following reaction in the synthesis of glucose ... 

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