NOH-1S is a voltage-gated proton channel that mediates the H(+) currents of resting phagocytes and other tissues. It participates in the regulation of cellular pH and is blocked by zinc. NOH-1L is a pyridine nucleotide-dependent oxidoreductase that generates superoxide and might conduct H(+) ions as part of its electron transport mechanism, whereas NOH-1S does not contain an electron transport chain. The oxidase activity is potentiated by NOXA1 and NOXO1. NOX1, NOXA1, NOXO1, RAC1 and CYBA forms a functional multimeric complex supporting reactive oxygen species (ROS) production. Interacts with NOXA1 and NOXO1. NOH-1L is detected in colon, uterus, prostate, and colon carcinoma, but not in peripheral blood leukocytes. NOH-1S is detected only in colon and colon carcinoma cells. Defects in NOX1 may play a role in the pathogenesis of very early onset inflammatory bowel disease (VEOIBD), a chronic, relapsing inflammation of the gastrointestinal tract with a complex etiology diagnosed before 6 years of age. VEOIBD is subdivided into Crohn disease and ulcerative colitis phenotypes. Crohn disease may affect any part of the gastrointestinal tract from the mouth to the anus, but the phenotype of children with onset of Crohn disease occurring younger than the age of 10 is predominantly colonic, with a lower risk of ileal disease. Bowel inflammation is transmural and discontinuous; it may contain granulomas or be associated with intestinal or perianal fistulas. In contrast, in ulcerative colitis, the inflammation is continuous and limited to rectal and colonic mucosal layers; fistulas and granulomas are not observed. Both diseases include extraintestinal inflammation of the skin, eyes, or joints.