Cytochrome b-245 alpha chain (CYBA)

Cytochrome b-245 alpha chain (CYBA, commonly known as p22phox) is a 22 kDa integral membrane protein forming part of the NADPH oxidase complex, where it heterodimerizes with the beta chain (NOX2/gp91phox) to form cytochrome b-245, the core enzyme for superoxide production in phagocytes. Upon activation by pathogens, NADPH oxidase assembles at the plasma or phagosomal membrane and initiates electron transfer from cytosolic NADPH, via FAD and heme moieties, to molecular oxygen—generating superoxide, a critical component of the microbicidal respiratory burst. CYBA is also expressed in endothelial and smooth muscle cells, where it partners with other NOX proteins (NOX1, NOX3, NOX4) to regulate reactive oxygen species in vascular biology. Genetic mutations in CYBA result in a rare form of chronic granulomatous disease due to defective superoxide generation, and specific polymorphisms have been linked to decreased oxidative stress and risk of cardiovascular disease. CYBA and NADPH oxidase are research targets for inhibitors in cardiovascular, inflammatory, and infectious pathologies, but safety concerns limit clinical translation.

Other names

cytochrome b-245 light chainp22phoxp22-PHOXCytochrome b(558) alpha chainCytochrome b558 subunit alphaNeutrophil cytochrome b 22 kDa polypeptideSuperoxide-generating NADPH oxidase light chain subunitp22 phagocyte B-cytochromeCytochrome b-245, alpha polypeptideflavocytochrome b-558 alpha polypeptideCGD4NADPH oxidase p22 subunitCyt b558 αnmf333Phox

Inhibition of NADPH oxidase assembly and/or electron transfer, leading to decreased production of superoxide and downstream reactive oxygen species; Blocking p22phox interaction impairs electron flow from NADPH to oxygen