Electrochemically coupled enzymatic reaction sequence

Figure 1. (a) Scheme for the reaction sequence of the electrochemically coupled enzymatic oxidation of glucose, (b) The effect of the enzymatic reaction on the electrochemistry of ferrocene using a gold disc of 25lim diameter at 5mV s... 

The number of substances that can be measured by monoenzymatic approaches in electrochemical biosensors is limited, because in the majority of biocatalytic reactions electrochemically active compounds are not involved. To form readily detectable species, different enzymatic reactions have to be coupled, as is already routine in wet biochemical analysis [13]. This coupling can be accomplished in ways analogous to those present in a living cell. Here, nature provides us a variety of ways of regulating metabolic pathways. Thus, like in nature, catalytic activities of different enzymes can be combined in biosensors either in sequence, competing pathways, or in cycles (Table 4). 

Enzyme electrodes comprising coimmobilized COD and CEH can be used for the determination of total cholesterol. On the other hand, coupling of COD with HRP enables cholesterol measurement at low electrode overvoltage, which avoids electrochemical interferences. Fig. 89 shows the diversity of the potential sequences of enzymatic and electrochemical reactions in cholesterol electrodes. 

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