Tryptase is the major neutral protease present in mast cells and is secreted upon the coupled activation-degranulation response of this cell type. Preferential cleavage: Arg-|-Xaa, Lys-|-Xaa, but with more restricted specificity than trypsin. Homotetramer. Released from the secretory granules upon mast cell activation. Expressed in colon, lung, heart and synovial tissue. May be specific to mast cells. Belongs to the peptidase S1 family. Tryptase subfamily. Although PubMed:11174199 reported this as a pseudogene, PubMed:12391231 showed it is expressed and has proteolytic activity when expressed in bacterial cells.