Activation of molecular oxygen by flavins and flavoproteins.

is essentially irreversible. In free solution the reaction is slow because of spin inversion associated with the reaction of singlet reduced flavin with triplet 0, and complex, as described below. With flavoproteins the reaction with 0, may be orders of magnitude faster or slower, depending on the specific flavoprotein or the class of flavoprotein to which i t belongs. Clearly the reactivity of the reduced flavin with 0, is modulated by the protein environment in which i t is located, both in terms of rates and products of the reaction (see Ref. 1 for a more detailed review).