ELECTRON-TRANSFER AND STABILITY OF A QUINOHEMOPROTEIN ALCOHOL-DEHYDROGENASE ELECTRODE

Quinohaemoprotein alcohol dehydrogenase from Comamonas testosteroni(QH -EDH) was immobilised in a redox polymer network of a polyvinylpyridin e, partially N-complexed with osmiumbis(bipyridine)chloride. Substrate -dependent electron transfer occurred, indicating that the enzyme was active and that effective electron transport was achieved. It was show n that the enzyme molecular weight is of importance with respect to th e enzyme electrode stability. Long term stability and current density of the th QH-EDH electrodes were highest when the enzyme was immobilis ed at pH 10.0 and 4 degrees C, followed by an additional cross-linking step with glutaraldehyde (1%) at ph 7.0. With such an electrode curre nt densities of 40 mu A cm(-2) were obtained for several primary alcoh ols. The affinity of the immoblised enzyme for these substrates (K-m(a pp) values) was similar to that of the enzyme in solution. The half-li fe time of the electrodes was between 50 h and 200 h depending on the time the enzyme was in contact with the substrate. When the immobilise d enzyme electrode was operated at temperatures above 37 degrees C the stability decreased.