MASP1, CRARF, CRARF1, PRSS5, Mannan-binding lectin serine protease 1, Complement factor MASP-3, Complement-activating component of Ra-reactive factor, Mannose-binding lectin-associated serine protease 1, Mannose-binding protein-associated serine protease, Ra-reactive factor serine protease p100, Serine protease 5, Mannan-binding lectin serine protease 1 heavy chain, Mannan-binding lectin serine protease 1 light chain

This gene encodes a serine protease that functions as a component of the lectin pathway of complement activation. The complement pathway plays an essential role in the innate and adaptive immune response. The encoded protein is synthesized as a zymogen and is activated when it complexes with the pathogen recognition molecules of lectin pathway, the mannose-binding lectin and the ficolins. This protein is not directly involved in complement activation but may play a role as an amplifier of complement activation by cleaving complement C2 or by activating another complement serine protease, MASP-2. The encoded protein is also able to cleave fibrinogen and factor XIII and may may be involved in coagulation. A splice variant of this gene which lacks the serine protease domain functions as an inhibitor of the complement pathway. Alternate splicing results in multiple transcript variants.