Polypyrrole entrapped quinohemoprotein alcohol dehydrogenase. Evidence fordirect electron transfer via conducting-polymer chains

It is reported for the first time that direct electron-transfer processes b etween a polypyrrole (PPY) entrapped quinohemoprotein alcohol dehydrogenase from Gluconobacter sp. 33 (QH-ADH) and a platinum electrode take place via the conducting-polymer network. The cooperative action of the enzyme-integ rated prosthetic groups-pyrroloquinoline-quinone and hemes-is assumed to al low this electron-transfer pathway from the enzyme's active site to the con ducting-polymer backbone. A hypothetical model of the electron transfer is proposed which is supported by the influence of various parameters, such as , e.g., ionic strength and nature of the buffer salts. This unusual electro n-transfer pathway leads to an accentuated increase of the K-M(app) value ( 102 mM) and hence to a significantly increased linear detection range of an ethanol sensor based on this enzyme.