NOX5

NOX5 (NADPH oxidase 5) is a calcium-regulated member of the NADPH oxidase family that generates reactive oxygen species (ROS), primarily superoxide, through electron transfer from NADPH to molecular oxygen, thereby linking intracellular calcium signaling to redox regulation^[1][2]. Mechanistically, calcium binding to the N-terminal EF-hand regulatory domain activates NOX5 and promotes conformational changes that facilitate electron transfer within the catalytic core, resulting in ROS production^[1][3]. Through this calcium-ROS signaling axis, NOX5 participates in physiological processes including sperm function, cell proliferation, vascular responses, and host-defense-related signaling pathways^[1][2]. In disease contexts, increased NOX5 expression or activity has been associated with cardiovascular disorders, diabetic nephropathy, renal injury, and multiple cancers, where excessive ROS production contributes to pathological signaling and tissue damage^[1][4]. Compared with related NOX isoforms, NOX5 is distinguished by its intrinsic calcium-sensing EF-hand domain and its ability to function without the classical cytosolic organizer and activator subunits required by several other NOX family members, making it one of the most self-contained ROS-generating oxidases^[3][5]. This distinctive regulatory architecture has made NOX5 an attractive experimental target for studying calcium-dependent oxidative stress and redox signaling. For research applications, pharmacological NOX5 inhibitors and transgenic disease models have been used to investigate the contribution of NOX5-derived ROS to vascular, renal, metabolic, and cancer-related pathophysiology^[1][4][5].