Chymostatin

Chymostatin is a bioactive peptide protease inhibitor that contains chymostatin A as a major form. The compound specifically inhibits chymotrypsin (CTR) (ID₅₀ = 150 ηg/ml), papain (ID₅₀ = 7.5 μg/ml), and cathepsin G along with most cysteine proteases such as cathepsin A, B, H, and L. The compound has been noted as a strong inhibitor of cathepsins A, B, and C. Chymostatin at an effective concentration of 10 to 100 μM weakly inhibits human leukocyte Elastase-1. In rat muscle homogenates chymostatin inhibited the protease cathepsin B and other soluble Ca²⁺ activated proteases. In the same study, chymostatin decreased protein break down by 20-40% without inhibiting protein production.