Chymases are a family of serine protease

Serine protease

Serine proteases are enzymes that cleave peptide bonds in proteins, in which serine serves as the nucleophilic amino acid at the active site.They are found ubiquitously in both eukaryotes and prokaryotes...

s found primarily in mast cell

Mast cell

A mast cell is a resident cell of several types of tissues and contains many granules rich in histamine and heparin...

s, though also present in basophil granulocyte

Basophil granulocyte

Basophil granulocytes, sometimes referred to as basophils, are the least common of the granulocytes, representing about 0.01% to 0.3% of circulating white blood cells....

s (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

Parasitism

Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...

 and parasite antigens promoting an inflammatory response. Chymases are also known to convert angiotensin

Angiotensin

Angiotensin, a peptide hormone, causes blood vessels to constrict, and drives blood pressure up. It is part of the renin-angiotensin system, which is a major target for drugs that lower blood pressure. Angiotensin also stimulates the release of aldosterone, another hormone, from the adrenal cortex...

 I to angiotensin II and thus play a role in hypertension

Hypertension

Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

 and atherosclerosis

Atherosclerosis

Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...

.

Because of its role in inflammation it has been investigated as a target in the treatment of asthma.