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.Chymostatin has been used in a study that determined that molecular calculations are useful for evaluating the interactions between ligands, including inhibitors and homologous enzymes, in docking models. Chymostatin has also been used in a study to investigate the norovirus protease as an attractive target for antiviral drμg development. 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.