Chymases (EC220.127.116.11, mast cell protease I, skeletal muscle protease, skin chymotryptic proteinase, mast cell serine proteinase, skeletal muscle (SK) protease) are a family of serine proteases found primarily in mast cells, though also present in basophil granulocytes (e.g. alpha chymase mcpt8). They show broad peptidolytic activity and are involved in a variety of functions. For example, chymases are released by mucosal mast cells upon challenge with parasites and parasite antigens promoting an inflammatory response. Chymases are also known to convert angiotensin I to angiotensin II and thus play a role in hypertension and atherosclerosis.
Because of its role in inflammation it has been investigated as a target in the treatment of asthma.