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Electron transfer studies with different sugar oxidizing enzymes and osmium polymers to improve the current density
|Muhammad N. Zafar 1, Xiaoju Wanga 2, Roland Ludwig 3, Donal Leech 4, Lo Gorton 1|
1. Lund University, Department of Analytical Chemistry and Biochemistry, Lund 22100, Sweden
|Glucose dehydrogenase (GDH) from Glomerella cingulata(GcGDH, EC 22.214.171.124) is an extracellular redox enzyme. The native enzyme is a monomeric glycosylated polypeptide and has one non-covalently bound flavin adenine dinucleotide (FAD) molecule acting as the redox cofactor. Pyranose dehydrogenase from Agaricus meleagris (AmPDH, EC 126.96.36.199) is an extracellular redox enzyme. The native enzyme is a monomeric glycosylated polypeptide and has a molecular mass of 66,547 Da, containing 7% carbohydrates and one covalently bound flavin adenine dinucleotide (FAD) molecule acting as the redox cofactor. PDH can oxidise its substrate at the C-1, C-2 or C-3 as well as perform double oxidation at C-1,2, C-2,3 and it has no anomeric specificity .
This new extracellular redox enzyme, flavin adenine dinucleotide (FAD) dependent glucose dehydrogenase from Glomerella cingulata(GcGDH) was electrochemically studied to catalyze the oxidation of glucose on spectrographic graphite electrode. Six Os polymers, whose redox potentials are ranged in a broad potential window between +15 and +489 mV vs. NHE, were used to “wire” the GcGDH on spectrographic graphite electrodes for possible applications in biosensors and biofuel cells. [2, 3]. The GcGDH/Os-polymer modified electrodes were evaluated in a chronoamperometric mode using FIA. The current response was investigated under a step-wisely increased potential window. The performance of the redox polymers for enzyme wiring was investigated using glucose as substrate. The current response was investigated under a step-wisely increased potential window. The ratio between GDH:Os-polymer was optimized. It was observed that the ratio between GDH:Os-polymer in the overall loading of the enzyme electrode significantly affects the performance of the enzyme electrode on catalyzing the glucose oxidation. The best Os-polymer had a potential of +309 mV vs. NHE and GcGDH:Os-polymer ratio was 1:2 yielding a maximum current density of 493 µAcm-2 for 30 mM glucose was produced by the GcGDH/Os c modified electrode.
After characterization of GcGDH, we coimmobilized equal units of GcGDH with AmPDH enzymes along with Os-polymer c on graphite electrodes to improve the current density. With this coimmobilization of both enzymes, we were successfully able to improve the current density. The reason for this improvement is that AmPDH enzyme also can oxidize the products of GcGDH enzyme due to its ability to oxidize at C-1, C-2 or C-3 as well as doubleoxidation at C-1,2, C-2,3.
 C.K. Peterbauer, J. Volc, Pyranose dehydrogenases: biochemical features and perspectives of technological applications, Appl. Microbiol. Biotechnol., 85 (2010) 837–848.
 Muhammad Nadeem Zafar, Federico Tasca, Susan Boland, Magdalena Kujawa, Ilabahen Patel, Clemens K. Peterbauer, Donal Leech, Lo Gorton, “Wiring of pyranose dehydrogenase with osmium polymers of different redox potentials”, Bioelectrochemistry, 80: 38-42 November 2010.
 F. Mao, N. Mano, A. Heller, Long tethers binding redox centers to polymer backbones enhance electron transport in enzyme “wiring” hydrogels, J. Am. Chem. Soc. 125 (2003) 4951–4957.
Presentation: Poster at SMCBS'2011 International Workshop, by Muhammad N. Zafar
See On-line Journal of SMCBS'2011 International Workshop
Submitted: 2011-08-29 12:51 Revised: 2011-09-22 14:58