Chemical Properties
This product is a kallikrein inhibitor extracted from bovine pancreas, lung, gill, and other tissues. It is not an enzyme itself, but a pear-shaped basic polypeptide composed of 58 amino acid residues, with a lysine active center. It competes with the active centers of various proteases for a lysine group, thereby inhibiting their activity. This product is a white or slightly yellowish powder, odorless, water-soluble, and dialyzable, with an isoelectric point of 10-10.5. It is stable to high temperatures, acids, bases, and enzymes. When heated to 100°C in dilute acid, it remains stable at pH 12.6 and room temperature for 24 hours, but its activity begins to decline at pH 12.8. It is digested by thermophilic proteases at 60-80°C and is not inactivated by other enzymes.
Biochem/physiol Actions
This inhibitor acts against trypsin, and chymotrypsin and plasmin to a lesser extent. It will also inhibit proteases with mechanisms similar to trypsin, plasma kallikrein and coagulation Factor X. The trypsin inhibitor will not act against metalloproteases, tissue-baseed kallikrein, acid proteases, or thio proteases. This inhibitor acts by forming a 1:1 stoichiometric complex with the protease active site, and then cleaving a single arginine-isoleucine bond on the inhibitor. The inhibition is both reversible and pH dependent.
