CYBA
MIM.608508 16q24
Cytochrome b(-245) is a heterodimer of the p91-phox beta polypeptide (CYBB) (phox for phagocyte oxidase) and a smaller p22-phox alpha polypeptide (CYBA) (MIM.608508).
Cytochrome b(-245) is an essential component of phagocytic NADPH-oxidase, a membrane-bound enzyme complex that generates large quantities of microbicidal superoxide and other oxidants upon activation.
Active NADPH oxidase also requires several cytosolic proteins, including NCF1 (p47-phox) (MIM.608512), NCF2 (p67-phox) (MIM.233710), NCF4 (p40-phox) (MIM.601488), and a GTP-binding protein, either RAC1 (MIM.602048) in macrophages or RAC2 (MIM.602049) in neutrophils.
This cytochrome b has a very low midpoint potential of -245 mV and a characteristic spectrophotometric absorption band at 558 nm, and is also known as cytochrome b(558). The CYBB gene product has also been referred to as cgd91-phox.
Pathology
mutations of CYBA in autosomal recessive cytochrome b-negative chronic granulomatous disease (CGD) (MIM.233690)
242T-CYBA polymorphism is associated with reduced risk of coronary artery disease (CAD) in Japanese.