Cytochrome b558 (gp91phox-p22phox complex) (Cyt b558)

The gp91phox-p22phox membrane flavocytochrome complex, commonly known as Cytochrome b558, is the catalytic core of the phagocyte NADPH oxidase (NOX2) system. It is a heterodimeric integral membrane protein consisting of a large glycosylated subunit (gp91phox or NOX2) and a smaller subunit (p22phox or CYBA). Upon activation, this complex recruits cytosolic regulatory proteins to transfer electrons from NADPH to molecular oxygen, generating superoxide anions as part of the respiratory burst essential for microbial killing (UniProt P04839, P13498). Mutations in either subunit lead to Chronic Granulomatous Disease (CGD), characterized by severe recurrent infections and granuloma formation due to the inability of phagocytes to produce reactive oxygen species (PubMed: 25222463). In addition to its role in host defense, overactivation of the complex is implicated in oxidative stress-related pathologies such as atherosclerosis, hypertension, and neurodegeneration (PubMed: 29038200). Therapeutic strategies targeting this complex aim to modulate ROS production, though selectivity remains a challenge to avoid compromising the innate immune response.

Other names

Flavocytochrome b558NADPH oxidase 2 complexNOX2-p22phox complexgp91phox-p22phox heterodimerPhagocyte NADPH oxidase

Inhibition of electron transfer from NADPH to molecular oxygen, preventing the formation of superoxide radicals; disruption of the assembly of cytosolic subunits (p47phox, p67phox, p40phox) with the membrane-bound cytochrome b558 complex.