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Oxygen reduction by cellobiose oxidoreductase: the role of the haem group
Author(s) -
Mason Maria G.,
Wilson Michael T.,
Ball Andrew,
Nicholls Peter
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(02)02633-9
Subject(s) - cellobiose dehydrogenase , chemistry , flavin group , oxidoreductase , catalase , superoxide dismutase , photochemistry , cofactor , oxygen , redox , phanerochaete , hydrogen peroxide , superoxide , cellobiose , enzyme , biochemistry , inorganic chemistry , organic chemistry , cellulase
We have used optical and electron paramagnetic spectroscopy to study the flavohaem enzyme cellobiose oxidoreductase (CBOR) from Phanerochaete chrysosporium . We have examined redox cycles of the enzyme in which the oxidation of cellobiose to cellobionolactone is coupled to the reduction of oxygen. During turnover flavin can reduce oxygen with one electron to produce superoxide or two electrons to produce hydrogen peroxide. Addition of superoxide dismutase significantly extended the time courses of these cycles, slowing the re‐oxidation rate of both cofactors. Addition of catalase also affected the haem time course, but to a lesser extent. Experiments in which superoxide was generated in the reaction mixture showed that this radical greatly enhanced the rate of haem re‐oxidation. From these results we propose a mechanism in which reactive oxygen species generation by CBOR flavin subsequently re‐oxidises CBOR haem. We discuss this mechanism in relationship to the biological function of this enzyme, namely lignocellulose degradation.