Cytosolic components of the phagocyte NADPH oxidase (p47phox, p67phox, and Rac2) translocate to the plasma membrane on cell activation where they interact with a membrane-bound cytochrome b to generate superoxide anion. Phosphorylation reactions are known to be important for activity of NADPH oxidase. Translocation of Rac2, p47phox, and p67phox were all enhanced in formyl-Met-Leu-Phe-stimulated neutrophils treated with 50 nM of the protein phosphatase 1/2A inhibitor calyculin A. Rac translocation was blocked by the tyrosine kinase inhibitors genistein (50 microM) and herbimycin (17 microM), whereas movement of p47phox and p67phox were not inhibited. Cell-free analysis of Rac translocation also demonstrated that translocation of p47phox and p67phox were not linked to the movement or availability of Rac2. Thus, Rac2 does not appear to regulate NADPH oxidase by controlling movements of the cytosolic components to the membrane-associated enzyme but may exert its effect at the level of the assembled complex. Tyrosine kinase activity is required for translocation of Rac in the chemoattractant-stimulated human neutrophil.