Enzymes, electrochemistry

The advancement in our understanding of mediated enzyme electrochemistry since the pioneering work of Hill and colleagues can be easily appreciated when it is realised that a commercial blood glucose sensor, the size of a pen, became commercially available only about a decade later. 

Occasionally, the analyst wishes to coulometrically quantify the amount of a redox-active material that is in solution, but finds that the material itself is electro-inactive. A good example of this is provided by enzyme electrochemistry. 

Much use has also been made of tunneling concepts in work on electron transfer from electrode to enzymes in solution, some of which adsorb on the electrode (Tarasevich, 1983). Most enzymes are huge in size (r > 50 A) compared with the hydrated ions usually considered. They contain a heme group that is a metal ion that must be reached by an electron if reduction is to occur. This would seem to introduce a hindrance to the development of the theoiy of enzyme electrochemistry. An electron... 

The first accounts that seemed to give direct enzyme electrochemistry were the reports concerning a soluble blue Cu oxidase, laccase, which catalyzed the rapid four-electron reduction of dioxygen to water. An efficient electrocatalysis of O2 reduction by adsorbed fungal laccase on pyrolytic graphite, glassy carbon, and C02-treated carbon black electrodes was first described by Tarasevich and co-workers (48). Several control experiments were carried out to verify direct electron transfer from the electrode to the Cu sites of the enzyme. 

Another example of enzyme electrochemistry is given by cytochrome c peroxidase (C( P). This monomer molecule contains a 5-type heme and catalyzes the two-electron reduction of H2O2 to water using cytochrome c (II) as the electron donor. In the process, the Fe(III) center of the enzyme reacts rapidly with H2O2 to yield a two-electron oxidized species, compound I, which is reduced to the Fe(III) form via another species, compound II. 

In this chapter we first describe components and the organization of some important biological redox systems. We then discuss advantages of electroactive polymers for this type of application and review the work so far in different areas of redox protein electrochemistry, redox enzyme electrochemistry, and redox... 

In contrast to the area of redox protein electrochemistry, redox enzyme electrochemistry has received much greater attention, driven in many cases by the desire to construct practical, self-contained enzyme electrodes for commercial applications. Redox enzyme electrochemistry is also easier to study in many ways because the substrate or product is often detected electrochemically rather than the enzyme itself. Various types of electroactive polymers have been used with redox enzymes, including redox polymers, redox-active hydrogels, and electropolymer-ized films of conducting and nonconducting, polymers. We discuss each type of polymer in turn, starting with electropolymerized films. 

Although the study of enzyme electrochemistry is of great value for the... 

Fig. 1 Schematic representation of studying enzyme electrochemistry and electrocatalysis...

Fleming BD, Johnson DL, Bond AM, Martin LL (2006) Recent progress in cytochrome P450 enzyme electrochemistry. Expert Opin Drug Metab Toxicol 2 581-589... 

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