Complement C1 inhibitor target proteases (C1-INH targets)

Complement C1 inhibitor (C1-INH) target proteases are a group of serine proteases that are physiologically regulated by the C1-INH protein, a member of the serpin superfamily (UniProt P05155). These targets include C1r and C1s of the classical complement pathway, mannan-binding lectin-associated serine proteases (MASP-1 and MASP-2), plasma kallikrein, and coagulation factors XIIa and XIa (Caldere et al., 2005). By forming irreversible covalent complexes with these enzymes, C1-INH acts as a master regulator of the complement, contact (kinin-kallikrein), and coagulation systems. A deficiency in the regulation of these proteases, typically due to low levels or dysfunctional C1-INH, leads to Hereditary Angioedema (HAE), characterized by overproduction of bradykinin and subsequent life-threatening episodes of tissue swelling (StatPearls, Hereditary Angioedema). Therapeutic agents, such as plasma-derived or recombinant C1-INH, function by replacing the missing inhibitor to suppress the overactivity of these target proteases (FDA, Cinryze Label). Monitoring these targets and their downstream effects, such as C4 levels, is essential for the management of inflammatory and vascular disorders.

Other names

C1 esterase inhibitor targetsSerpin G1 targetsPlasma serine proteasesComplement component 1 inhibitor targets

C1 inhibitor acts as a suicide substrate for its target proteases; it forms a 1:1 stoichiometric covalent complex with the active site of the serine protease, leading to irreversible inhibition and preventing the cleavage of downstream substrates such as C4 and high-molecular-weight kininogen (StatPearls, Hereditary Angioedema; UniProt P05155).