Cellobiose dehydrogenase

Cellobiose dehydrogenase oxidizes cellobiose to cellobionolactone and transfers the electrons to a wide range of electron acceptors. The oxidized enzyme is 

Cameron and Aust have examined the electron-transfer processes between the two domains using EPR and stopped-flow spectroscopy. FAD was found to be the direct electron donor for the transfer of electrons to all substrates tested, including cytochrome c. A comphcated interaction was found to exist between the FAD and heme cofactors. The addition of electron acceptors was shown to increase the rate of flavin oxidation and the electron-transfer rate between the flavin and heme, although the heme itself was not involved in the direct transfer of electrons to substrate. 

The addition of Fe eliminated the flavin radical present in reduced cel-lobiose dehydrogenase, while it increased the flavin radical EPR signal when only the reduced cellobiose quinone oxidoreductase domain was tested, proving that the flavin is fully reduced in the latter. No radical was detected in either system upon the addition of methyl-1,4-benzoquinone. The authors concluded that the site of substrate reduction may be in the cleft between the flavin and heme domains. 

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Since the primary structure of a peptide determines the global fold of any protein, the amino acid sequence of a heme protein not only provides the ligands, but also establishes the heme environmental factors such as solvent and ion accessibility and local dielectric. The prevalent secondary structure element found in heme protein architectures is the a-helix however, it should be noted that p-sheet heme proteins are also known, such as the nitrophorin from Rhodnius prolixus (71) and flavocytochrome cellobiose dehydrogenase from Phanerochaete chrys-osporium (72). However, for the purpose of this review, we focus on the structures of cytochromes 6562 (73) and c (74) shown in Fig. 2, which are four-a-helix bundle protein architectures and lend themselves as resource structures for the development of de novo designs. 

Glucose was determined by the glucose oxidase-peroxidase method. Cellobiose (liberated enzymatically from methylcellotrioside) was determined in a coupled assay using cellobiose dehydrogenase from Sporotrichum thermophile (4). 

Heme Cytochrome c Cytochrome c oxidase, cytochrome c peroxidase, cellobiose dehydrogenase, nitrate reductase, sulphite oxidase, theophylline oxidase, cytochrome 62... 

Detailed mechanistic studies were also published by (jorton s group for the flavohemoprotein cellobiose dehydrogenase [8,26,109,110,225,226]. 

The most common reaction at the anodic side of biofuel cells is the oxidation of sugars which relies on the catalytic properties of oxidases. This class of enzymes has, however, usually poor potential for direct ET. Direct ET on the anodic site was, however, described for a number of hydrogenases [235, 236] and cellobiose dehydrogenase [225, 237, 238]. Enzymatic catalysis by means of direct ET was also realized on conducting graphite or TiO2 particles [239, 240]. 

Lindgren, A., Larsson, T., Ruzgas, T., and Gorton, L. (2000) Direct electron transfer between the heme of cellobiose dehydrogenase and thiol modified gold electrodes. Journal of Electroanalytical Chemistry, 494 (2), 105-113. 

Direct electron transfer-a favorite electron route for cellobiose dehydrogenase (CDH) from Trametes villosa. Comparison with CDH from Phanerochaete chrysosporium. Langmuir, 22 (25), 10801-10806. 

Ludwig, R., Harreither, W., Tasca, F., and Gorton, L. (2010) Cellobiose dehydrogenase a versatile catalyst for electrochemical applications. ChemPhysChem, 11 (13), 2674-2697. 

Stoica, L, Ludwig, R., Haltrich, D., and Gorton, L. (2006) Third-generation biosensor for lactose based on newly discovered cellobiose dehydrogenase. Analytical Chemistry, 78 (2), 393-398. 

T Dumonceaux, K Bartholomew, L Valeanu, T Charles, F Archibald. Cellobiose dehydrogenase is essential for wood invasion and nonessential for kraft pulp delignification by Trametes versicolor. EnzMicrob Technol 29(8-9) 478-489, 2001. 

Sigoillot, C., Lomascolo, A., Record, E., Robert, J. L., Asther, M., Sigoillot, J. C. (2002). Lignoeellulolytic and hemicellulolytic system of Pycnoporus cinnabarinus isolation and characterization of a cellobiose dehydrogenase and a new xylanase. Enzyme and Microbial Technology, 31, 876-883. 

Fridman, V., Wollenberger, U., Bogdanovskaya, V., Lisdat, F., Ruzgas, T., Lindgren, A., Gorton, L., Scheller, F. W. (2000). Electrochemical investigation of cellobiose oxidation by cellobiose dehydrogenase in the presence of cytochrome c as mediator. Biochem Soc Trans 28, 63-70. 

Cellobiose Dehydrogenase An Extracellular Flavocytochrome from the Phytopathogenic Basidiomycete Sclerotium (Athelia) rolfsii... 

S. rolfsii is known to produce cellulolytic and hemicellulolytic enzymes in high amounts (1-3), as a matter of fact it has been recognized as one of the few producers of these hydrolases that are of industrial interest (4). S. rolfsii secretes a complete cellulose degrading enzyme system consisting of endoglucanases (5, 6), cellobiohydrolases (7), and (3-D-glucosidases (8) which have been isolated and characterized extensively in the past. In addition, cellobiose dehydrogenase was reported as part of the cellulolytic enzyme system of S, rolfsii (9, 10). 

Table II. Apparent Kinetic Constants of Cellobiose Dehydrogenase from Sclerotium rolfsii for Different Electron Donors...

Figure 2 Unrooted phylogenetic tree for eight protein sequences of cellobiose dehydrogenases. The numbers in nodes represent bootstrap values for 100 replicates. The scale bar indicates the branch length corresponding to 0.1 amino acid substitutions per site.

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