Functions as an activator of NOX1, a superoxide-producing NADPH oxidase. Functions in the production of reactive oxygen species (ROS) which participate in a variety of biological processes including host defense, hormone biosynthesis, oxygen sensing and signal transduction. May also activate CYBB/gp91phox and NOX3. NOX1, NOXA1, NOXO1, RAC1 and CYBA forms a functional multimeric complex supporting ROS production. Interaction with YWHAZ prevents the interaction of NOXA1 with NOXO1 and RAC1 and its targeting to membranes, hence reducing its ability to activate NOX1. Interacts (via N-terminus) with SH3PXD2A and SH3PXD2B; the interaction is direct (By similarity). Translocation to membranes depends on NOXO1 or NCF1 and maybe RAC1. Widely expressed with a tissue distribution similar to the one of NOX1. Detected in colon, uterus, prostate, small intestine, stomach, lung, thyroid, aorta, inner ear and salivary glands. Expressed in colon, small intestine and aortic smooth muscle cells (at protein level). The SH3 domain mediates interaction with NOXO1 and NCF1 and has autoregulatory function. The TPR repeats mediate interaction with RAC1. Belongs to the NCF2/NOXA1 family.