CMA1 is a chymotryptic serine proteinase that belongs to the peptidase family S1. It is a major secreted protease of mast cells and is involved in vasoactive peptide generation, extracellular matrix degradation, tissue remodeling, and the regulation of submucosal gland secretion. In the heart and blood vessels, this protein, rather than angiotensin converting enzyme, is largely responsible for converting angiotensin I to the vasoactive peptide angiotensin II. Mast cell chymases have been implicated in a variety of cardiovascular and metabolic diseases such as atherosclerosis, abdominal aortic aneurysms, obesity, and diabetes.