UniProt Summary: Constitutively potentiates the superoxide-generating activity of NOX1 and NOX3 and is required for the biogenesis of otoconia/otolith, which are crystalline structures of the inner ear involved in the perception of gravity. Isoform 3 is more potent than isoform 1 in activating NOX3. Together with NOXA1, may also substitute to NCF1/p47phox and NCF2/p67phox in supporting the phagocyte NOX2/gp91phox superoxide-generating activity. {ECO:0000269|PubMed:12657628, ECO:0000269|PubMed:14617635, ECO:0000269|PubMed:15326186, ECO:0000269|PubMed:15824103, ECO:0000269|PubMed:15949904, ECO:0000269|PubMed:16329988, ECO:0000269|PubMed:17126813, ECO:0000269|PubMed:19755710}.