title: Electrocatalytic reduction of lipoic acid and electroenzymatic reduction of NAD(P)(+) for integrated dehydrogenase biosensors.
abstract: Biosensors for the oxidized substrates of NAD(P)(+)-specific dehydrogenases demand the reductive recycling of the coenzymes. So far, suitable catalysts for the corresponding two-electron transfer are not available. In the present paper, this transport has been realized by a combined electrocatalytical and electroenzymatic process. Lipoic acid has been reduced on graphite electrodes functionalized with Fe(II)-phthalocyanine in 95% yield at-1200 mV in phosphate buffer pH 7.0. With the electrocatalytically reduced product, dihydrolipoic acid, lipoamide dehydrogenase could reduce NAD(+) in 20% yield and thioredoxin reductase NADP(+) in 18.4% yield. So far, the combined electrocatalytic/electroenzymatic system has not yet been realized, mainly because at the potential needed for the lipoic acid reduction, a parallel one-electron reduction of NAD(P)(+) was observed, implying the dimerization of the coenzyme.
authors.affiliation: Lehrstuhl für Biologische Chemie, Technische Universität München, An der Saatzucht 5, D-85350 Freising-Weihenstephan, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Eicher
authors.forename: H L
authors.initials: HL
authors.lastname: Schmidt
mesh_terms: D015374:Biosensing Techniques; D002384:Catalysis; D009252:NADPH Dehydrogenase / Q000032:analysis / Q000737:chemistry*; D013379:Substrate Specificity; D008063:Thioctic Acid / Q000032:analysis / Q000737:chemistry*
chemical_list: D008063:Thioctic Acid; D009252:NADPH Dehydrogenase