Pyrroloquinoline Quinone PQQ dependent Glucose Dehydrogenase

The reduced cofactor can be reoxidised by two one-electron-transfers, for example the common oxidant ubiquinone. 

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Zhao, C., Wittstock, G. Scanning electrochemical microscopy for detection of biosensor and biochip surfaces with immobilized pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase as enzyme label. Biosens Bioelectron 2005, 20, 1277-1284. 

An alternative biosensor system has been developed by Hart et al. [44] which involves the use of the NAD+-dependent GDH enzyme. The first step of the reaction scheme involves the enzymatic reduction of NAD+ to NADH, which is bought about by the action of GDH on glucose. The analytical signal arises from the electrocatalytic oxidation of NADH back to NAD+ in the presence of the electrocatalyst Meldola s Blue (MB), at a potential of only 0Y. Biosensors utilising this mediator have been reviewed elsewhere [1,17]. Razumiene et al. [45] employed a similar system using both GDH and alcohol dehydrogenase with the cofactor pyrroloquinoline quinone (PQQ), the oxidation of which was mediated by a ferrocene derivative. 

The other less common type of phenol biosensor involves enzymes like PQQ (pyrroloquinoline quinone)-dependent glucose dehydrogenase (GDH) (9-12) or... 

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