Chymostatin is a bioactive peptide of microbial origin that acts as a protease inhibitor with selectivity for chymotryptase-like serine proteases. It potently inhibits chymotrypsin and chymase (Ki = 9.36 and 13.1 nM, respectively) while less effectively blocking the activity of cathepsins, papain, and leukocyte elastase. It is without effect on trypsin, thrombin, plasmin, pepsin, and kallikrein.
