Mast cells are connective tissue cells derived from blood-forming tissues that line arterial walls and secrete substances, which mediate inflammatory and immune responses. Mast Cell Chymase, also known as CMA1 or MCT1, is a major secreted serine protease that is involved in vasoactive peptide generation, extracellular matrix degradation and regulation of gland secretion. The human chymase gene, which maps to human chromosome 14q11.2, encodes a preproenzyme with a 19 amino acid signal peptide, an acidic 2 amino acid propeptide and a 226 amino acid catalytic domain. Mast Cell Chymase is a chymotryptic serine proteinase which is a member of the peptidase family S1. Expressed in mast cells, Mast Cell Chymase is associated with the degradation of the extracellular matrix, the regulation of submucosal gland secretion, and the generation of vasoactive peptides. Mast cell proteases are a family of rodent protein homologs to human tryptases that are specifically expressed in mast cells and may serve as highly specific markers in the analysis of mast cell heterogeneity, differentiation and function. Mast Cell Protease 1, also designated Mcp-1 or Mcpt1, is a rodent specific beta-chymase. The mouse and rat Mast Cell Protease 1 proteins share 76% sequence identity at the amino acid level.