| Mast cell chymase (chymase 1, CMA1) is a chymotrypsin-like serine protease stored in secretory granules of connective tissue–type mast cells and released upon activation, where it functions as a multifunctional effector enzyme that processes peptides, cytokines, and matrix components at sites of inflammation and tissue remodeling. The enzyme adopts the typical trypsin/chymotrypsin fold with a catalytic His–Asp–Ser triad in a substrate-binding cleft that prefers aromatic residues at the P1 position, and its heparin-dependent packing into mast cell granules positions chymase for rapid, localized proteolysis after degranulation. Angiotensin I represents a key physiological substrate, and human chymase efficiently converts angiotensin I to angiotensin II in the interstitial space, providing a major non–ACE pathway for angiotensin II generation in the heart and vasculature and contributing to local regulation of vascular tone, cardiac remodeling, and atherogenesis. Chymase also processes components of the extracellular matrix and matrix-regulating systems, including activation of matrix metalloproteinases and processing of type I procollagen, which link mast cell degranulation to collagen turnover, fibrotic matrix deposition, and structural changes in the vessel wall and parenchymal organs. Cytokine and growth factor bioavailability is strongly influenced by chymase, which can convert pro–IL‑1β to its active form, degrade IL‑4, and induce release of membrane-bound stem cell factor, thereby modulating local inflammatory cell recruitment, T helper cell polarization, and mast cell survival in a feedback-sensitive manner. Chymase functions as a chemoattractant for leukocytes and promotes migration of eosinophils and other inflammatory cells through protease-activated mechanisms and through remodeling of pericellular matrix, integrating mast cell activation with downstream recruitment and activation of effector leukocytes in allergic and chronic inflammatory settings. In airway disease, mast cell chymase contributes to airway smooth muscle and submucosal remodeling by degrading pericellular matrix, stimulating collagen fibril formation, and enhancing TGF‑β activation, aligning chymase activity with bronchial hyperresponsiveness, airway wall thickening, and features of asthma and chronic obstructive pulmonary disease. Cardiovascular pathologies, including hypertension, myocardial infarction, aneurysm formation, and valvular disease, are associated with increased mast cell chymase activity, where its angiotensin II–generating capacity, matrix-modifying actions, and pro-fibrotic signaling roles converge to drive adverse remodeling, neovascularization, and plaque instability. |
Immunohistochemical analysis of formalin fixed paraffin embedded human colon tissue with F8677 at 1:50 dilution.
