Sensors apoenzyme

An apoenzyme electrode for Cu2+ has been developed by the coupling of immobilized apo-tyrosinase with an oxygen probe (Mattiasson et al., 1979). The detection limit of the sensor was 50 ppm. However, the reusability of such an apoenzyme membrane appears to be questionable because the enzyme activity accumulates during the operation of the sensor whereas the measuring principle requires kinetic control so as to obtain a linear dependence of the sensitivity on the activity of the holoenzyme. 

Biosensors for inhibitor determination are based on the ability of inhibiting substances to become bound to the receptor component and decelerate the substrate conversion. Therefore, inhibitor sensors, similar to apoenzyme sensors and immunosensors, combine the affinity principle with enzymatic amplification reactions. In contrast to metabolism sensors, the binding is evaluated rather than the chemical reaction of the analyte. 

Biosensors, known to monitor various analytes both selectively and sensitively, have also been reported for heavy metal detection. Several electrode configurations using whole cells, enzymes or apoenzymes have been designed 4-6). The main advantage of such biosensors is that samples often require little pretreatment and the bioavailable concentration of the toxic heavy metal is measured, rather than the total concentration. However, a limited selectivity and quite low sensitivity characterize these sensors described in the literature. 

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