Nox4, a novel homologue of the phagocyte NADPH oxidase catalytic subunit gp91^phox

During phagocytosis, the NADPH oxidase in neutrophils produces superoxide, a precursor of microbicidal oxidants, thereby playing a crucial role in host defense. The phagocyte oxidase contains the two subunits p22^phox and gp91^phox, the latter of which contains binding sites for the heme, FAD, and NADPH, forming the complete electron-transporting apparatus. Recent studies have revealed that four nonphagocytic homologues of gp91^phox exist, including Nox4, whose cDNA we have currently cloned. Here we describe the molecular nature of Nox4, in comparison with those of other members of the NAD(P)H oxidase family.