The superoxide-producing phagocyte NADPH oxidase gp91(phox)/Nox2 and the 
non-phagocytic oxidases Nox1 and Nox3 each form a complex in the membrane with 
p22(phox), which provides both stabilization and a docking site for organizer 
proteins. The p22(phox)-complexed Nox2 and Nox1 are dormant on their own, and 
their activation requires soluble supportive proteins such as a Nox organizer 
(p47(phox) or Noxo1) and a Nox activator (p67(phox) or Noxa1). The small GTPase 
Rac directly binds to the activators, and thus plays an essential role in the 
Nox2-based oxidase containing p47(phox) and p67(phox) or a positive role in Nox1 
activity supported by Noxo1 and Noxa1. Although Nox3 complexed with p22(phox) 
constitutively produce superoxide, the production can be enhanced by supportive 
proteins. Here we compare the roles of Rac in these p22(phox)-dependent oxidases 
using the organizer and activator in different combinations. Expression of 
constitutively active Rac1(Q61L) is essential for activation of the Nox2- or 
Nox1-based oxidase containing the organizer p47(phox) and either p67(phox) or 
Noxa1. When these oxidases use Noxo1 as an organizer instead of p47(phox), they 
produce a small but significant amount of superoxide without expression of 
Rac1(Q61L), although the production is enhanced by Rac1(Q61L). Thus p47(phox) is 
likely related to strict dependence on Rac. The Nox3-based oxidase has a similar 
tendency in the change of the dependence: Rac plays a positive role in Nox3 
activation in the presence of p47(phox) and either p67(phox) or Noxa1, whereas 
Rac fails to upregulate Nox3 activity when p47(phox) is replaced with Noxo1. We 
also demonstrate that, in the Nox3-based oxidase containing solely p67(phox) as 
supportive protein, expression of Rac1(Q61L) enhances not only superoxide 
production but also membrane translocation of p67(phox). Since the enhancements 
are not observed with a mutant p67(phox) defective in binding to Rac, this 
GTPase appear to directly recruit p67(phox) to the membrane.