Complement Factor B (C3 Proactivator; C3PA; Complement 3 Proactivator; Factor B; Properdin Factor B)
A glycine-rich, heat-labile serum glycoprotein that contains a component of the C3 CONVERTASE ALTERNATE PATHWAY (C3bBb). Bb, a serine protease, is generated when factor B is cleaved by complement factor d into Ba and Bb.