Apr 11, 2003

The heme domain of cellobiose oxidoreductase: a one-electron reducing system

Biochimica Et Biophysica Acta
Maria G MasonMichael T Wilson

Abstract

Phanerochaete chrysosporium cellobiose oxidoreductase (CBOR) comprises two redox domains, one containing flavin adenine dinucleotide (FAD) and the other protoheme. It reduces both two-electron acceptors, including molecular oxygen, and one-electron acceptors, including transition metal complexes and cytochrome c. If the latter reacts with the flavin, the reduced heme b acts merely as a redox buffer, but if with the b heme, enzyme action involves a true electron transfer chain. Intact CBOR fully reduced with cellobiose, CBOR partially reduced by ascorbate, and isolated ascorbate-reduced heme domain, all transfer electrons at similar rates to cytochrome c. Reduction of cationic one-electron acceptors via the heme group supports an electron transfer chain model. Analogous reactions with natural one-electron acceptors can promote Fenton chemistry, which may explain evolutionary retention of the heme domain and the enzyme's unique character among secreted sugar dehydrogenases.

Mentioned in this Paper

Fast Electrons
Cellobiose
Electron Transport
Ascorbate
Cellobiose oxidase
Spectrophotometry
Ascorbate Measurement
Cell Secretion
Oxidation-Reduction
Flavins

About this Paper

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