NADPH oxidase enzymes share the capacity to transport electrons across the plasma membrane and generate superoxide and other down-stream reactive oxygen species (ROS).

Seven homologues of the cytochrome subunit of the NADPH oxidase have been found:

NOX1, NOX2, NOX3, NOX4, NOX5, DUOX1 and DUOX2

and are now referred to as the NOX family of NADPH oxidases.