In the O2– generating flavocytochrome b, the membranebound component of the neutrophil NADPH oxidase, electrons are transported from NADPH to O2 in the following sequence: NADPH fi FAD fi heme b fi O2. Although p-iodonitrotetrazolium (INT) has frequently been used as a probe of the diaphorase activity of the neutrophil flavocytochrome b, the propensity of its radical to interact reversibly with O2 led us to question its specificity. This study was undertaken to reexamine the interaction of INT with the redox components of the neutrophil flavocytochrome b. .
