MECHANISM OF INHIBITION. OR PEPSIN BY PEPSTATIN
MECHANISM OF INHIBITION. OR PEPSIN BY PEPSTATIN Pepstatin, a specific inhibitor of acid proteases, binds tightly to pepsin. Although the binding is not of the covalent nature, the inhibition roughly follows the stoicheometrical mode. Pepstatin can be used to titrate pepsin. Formation of an equimolar pepsin-pepstatin complex can be shown by gel filtration. Diacetylpepstatin, which has weaker activity than pepstatin com- petitively inhibits pepsin with a dissociation constant of 7.3XlO"6M. Data of pepstatin binding of chemically modified pepsins suggested that pepstatin binds with the active site surrounded by two aspartic acid moieties. Pepstatin, isovaleryl-L-valyl-L-valyl-4-amino-3-hydroxy-6-methylheptanoyl-L- alanyl-4-amino-3-hydroxy-6-methylheptanoic acid, was discovered in streptomyces culture nitrates and has been shown to be a specific inhibitor of acid proteases1*2'^. It shows a strong protective effect against pylorus-ligated rat stomach ulcer, and an effect...