Triiodide reduction by cellobiose: quinone oxidoreductase ofPhanerochaete chrysosporium

Abstract
Cellobiose: quinone oxidoreductase (CBQase) in the presence of cellobiose inhibits peroxidase-catalyzed oxidation of iodide to triiodide (I3,−). This inhibition is due to the two-electron reduction of I−3 by CBQase. The apparent Km of I−3 for this reaction is 120 μM and the specific activity is 57 μmol·min−1·mg−1. A proposed mechanism for I−3 reduction by CBQase involves initial reduction of the flavin moiety by cellobiose to produce a dihydroflavin. This is followed by the substitution of one of the iodine atoms of I−3 at the C(4a)-position of dihydroflavin to generate C(4a)-iododihydroflavin and two iodide ions. The C(4a)-iododihydroflavin eliminates HI to regenerate the oxidized CBQase

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