The activity of the non-phagocytic NADPH oxidase 1 (NOX1) complex, composed of NOX1, NOXA1, NOXO1 and CYBA, is greatly enhanced upon RAC1:GTP binding, resulting in production of the superoxide O2- which can serve as a second messenger (Takeya et al. 2003, Miyano et al. 2006, Park et al. 2006, Cheng et al. 2006).