Kinetic behaviour of dopamine polyphenol oxidase on electrodes of tetrathiafulvalenium tetracyanoquinodimethanide and tetracyanoquinodimethane species

This paper presents a study of the electrochemical behaviour of polyphenol oxidase onto-conducting organic salt electrodes using dopamine as enzymatic substrate. The enzyme is immobilized behind a dialysis membrane. TTF.TCNQ and carbon paste with TCNQ(0) and NaTCNQ are employed, and the role of the different salt components as enzyme regeneration mediators is analysed unde r anaerobic conditions. It: is concluded that both TCNQ(0) and NaTCNQ speci es are able to regenerate the active enzyme although chemical reactions bet ween the species make it difficult to discriminate their behaviour. Results strongly suggest a heterogeneous mechanism for the enzymatic reaction and NaTCNQ as enzymatic regenerator on TTF.TCNQ, apparent Michaelis-Menten cons tants are evaluated. The results clearly point to an enzymatic control of t he reaction rate under our experimental conditions. A chemical catalytic ef fect due to coupled chemical reactions is also described. The biosensors an alysed are potentially useful from the analytical point of view. Different electrode materials were analysed: TTF.TCNQ and carbon paste with TCNQ(0) a nd NaTCNQ. (C) 1999 Elsevier Science S.A. All rights reserved.