VPs (versatile peroxidases) sharing the functions of LiP (lignin peroxidase) and MnP (manganese peroxidase) have been described in basidiomycetous fungi Pleurotus and Bjerkandera. Despite the importance of this enzyme in polymer degradation, its reactivity with polymeric substrates remains poorly understood. In the present study, we first report that, unlike LiP, VP from Pleurotus ostreatus directly oxidized two polymeric substrates, bovine pancreatic RNase and Poly R-478, through a long-range electron pathway without redox mediators. P. ostreatus produces several MnP isoenzymes, including the multifunctional enzyme MnP2 (VP) and a typical MnP isoenzyme MnP3. MnP2 (VP) depolymerized a polymeric azo dye, Poly R-478, to complete its catalytic cycle. Reduction of the oxidized intermediates of MnP2 (VP) to its resting state was also observed for RNase. RNase inhibited the oxidation of VA (veratryl alcohol) in a competitive manner. Blocking of the exposed tryptophan by N-bromosuccinimide inhibited the oxidation of RNase and VA by MnP2 (VP), but its Mn2+-oxidizing activity was retained, suggesting that Trp-170 exposed on an enzyme surface is a substrate-binding site both for VA and the polymeric substrates. The direct oxidation of RNase and Poly R by MnP2 (VP) is in sharp contrast with redox mediator-dependent oxidation of these polymers by LiP from Phanerochaete chrysosporium. Molecular modelling of MnP2 (VP) revealed that the differences in the dependence on redox mediators in polymer oxidation by MnP2 (VP) and LiP were explained by the anionic microenvironment surrounding the exposed tryptophan.
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Research Article|
February 22 2005
Direct oxidation of polymeric substrates by multifunctional manganese peroxidase isoenzyme from Pleurotus ostreatus without redox mediators
Hisatoshi KAMITSUJI;
Hisatoshi KAMITSUJI
*Laboratory of Biomass Conversion, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
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Takashi WATANABE;
Takashi WATANABE
1
*Laboratory of Biomass Conversion, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
1To whom correspondence should be addressed (email twatanab@rish.kyoto-u.ac.jp).
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Yoichi HONDA;
Yoichi HONDA
*Laboratory of Biomass Conversion, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
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Masaaki KUWAHARA
Masaaki KUWAHARA
†Institute of Wood Technology, Akita Prefectural University, Kaieizaka, Noshiro, Akita 016-0876, Japan
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Biochem J (2005) 386 (2): 387–393.
Article history
Received:
June 08 2004
Revision Received:
September 27 2004
Accepted:
October 04 2004
Accepted Manuscript online:
October 04 2004
Citation
Hisatoshi KAMITSUJI, Takashi WATANABE, Yoichi HONDA, Masaaki KUWAHARA; Direct oxidation of polymeric substrates by multifunctional manganese peroxidase isoenzyme from Pleurotus ostreatus without redox mediators. Biochem J 1 March 2005; 386 (2): 387–393. doi: https://doi.org/10.1042/BJ20040968
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