Component C2 which is part of the classical pathway of the complement system is cleaved by activated factor C1 into two fragments: C2b and C2a. C2a, a serine protease, then combines with complement factor 4b to generate the C3 or C5 convertase.
Defects in C2 are the cause of complement component 2 deficiency (C2D) [MIM:217000]. A deficiency of the complement classical pathway associated with the development of autoimmune disorders, mainly systemic lupus erythematosus. Skin and joint manifestations are common and renal disease is relatively rare. Patients with complement component 2 deficiency are also reported to have recurrent or invasive infections.
Belongs to the peptidase S1 family. Contains 1 peptidase S1 domain. Contains 3 Sushi (CCP/SCR) domains. Contains 1 VWFA domain.