Pancreatic Trypsin Inhibitor (Kunitz) Part I " Structure and Function

A large variety of polypeptide inhibitors for proteolytic enzymes occurs in plants and animals. Although their physiological function is not known in detail, they appear to function by limiting the area available for, as well as the duration of, proteolytic processes. The basic pancreatic trypsin inhibitor (in the following, PTI inhibitor or inhibitor) was found in bovine pancreas and other organs (Kraut et al., 1930; Kunitz and Northrop, 1936). Its physio-logical function is largely unknown. As it occurs only in some ruminants, it could play some part in the relationship between the organism and the special fauna of the gastrointestinal tract (Vogel et al., 1968). The PTI inhibitor has a molecular weight of 6500 and consists of 58 amino acids, whose sequence has been determined in severa