Figure 1.

Schematic representation of the inactive and active forms of the NADPH oxidase complex. The complex consists of six subunits. NOX2 and p22phox are associated to form a heterodimer bound to the plasma membrane in both the inactive and the active forms. In resting conditions, p47phox, p67phox, p40phox, and the G-protein Rac are located in the cytosol. In the active form, the cytosolic subunits associate with the membrane-bound NOX2/p22phox heterodimer. The active NADPH oxidase generates superoxide (O₂ ⁻) by transferring electrons from NADPH inside the cell across the membrane and coupling them to molecular oxygen.