Mast cell tryptase is the main neutral protease secreted by mast cells. It is the main component of mast cell secretory granules. It is the most abundant protein in mast cells, accounting for more than 50% of the total protein of mast cell secretory granules. It is widely distributed in respiratory tract, gastrointestinal tract, skin and other tissues. It plays an important role in the pathological process of inflammatory diseases such as cell infection and injury, especially bronchoconstrictive asthma. It is used in the study of respiratory and gastrointestinal diseases.