TAILIEUCHUNG - Báo cáo khoa học: Electron transfer chain reaction of the extracellular flavocytochrome cellobiose dehydrogenase from the basidiomycete Phanerochaete chrysosporium

Cellobiose dehydrogenase (CDH) is an extracellular flavocytochrome con-taining flavin and b-type heme, and plays a key role in cellulose degrada-tion by filamentous fungi. To investigate intermolecular electron transfer from CDH to cytochrome c, Phe166, which is located in the cytochrome domain and approaches one of propionates of heme, was mutated to Tyr, and the thermodynamic and kinetic properties of the mutant (F166Y) were compared with those of the wild-type (WT) enzyme. | ềFEBS Journal Electron transfer chain reaction of the extracellular flavocytochrome cellobiose dehydrogenase from the basidiomycete Phanerochaete chrysosporium Kiyohiko Igarashi1 Makoto Yoshida1 Hirotoshi Matsumura2 Nobuhumi Nakamura2 Hiroyuki Ohno2 Masahiro Samejima1 and Takeshi Nishino3 1 Department of Biomaterials Sciences Graduate Schoolof Agriculturaland Life Sciences The University of Tokyo Japan 2 Department of Biotechnology Tokyo University of Agriculturaland Technology Japan 3 Department of Biochemistry and Molecular Biology Nippon Medical School Tokyo Japan Keywords cellobiose dehydrogenase cellulose degradation electron-transfer Phanerochaete chrysosporium Correspondence K. Igarashi Department of Biomaterials Sciences Graduate School of Agricultural and Life Sciences The University of Tokyo Bunkyo-ku Tokyo 113-8657 Japan Fax 81 3 5841 5273 Tel 81 3 5841 5258 E-mail aquarius@ Received 27 February 2005 revised 26 March 2005 accepted 6 April 2005 doi Cellobiose dehydrogenase CDH is an extracellular flavocytochrome containing flavin and b-type heme and plays a key role in cellulose degradation by filamentous fungi. To investigate intermolecular electron transfer from CDH to cytochrome c Phe166 which is located in the cytochrome domain and approaches one of propionates of heme was mutated to Tyr and the thermodynamic and kinetic properties of the mutant F166Y were compared with those of the wild-type WT enzyme. The mid-point potential of heme in F166Y was measured by cyclic voltammetry and was estimated to be 25 mV lower than that of WT at pH . Although presteady-state reduction of flavin was not affected by the mutation the rate of subsequent electron transfer from flavin to heme was halved in F166Y. When WT or F166Y was reduced with cellobiose and then mixed with cytochrome c heme re-oxidation and cytochrome c reduction occurred synchronously suggesting that the initial electron is transferred from .

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