Purification of canine pancreatic secretory trypsin inhibitor and interaction in vitro with complexes of trypsin-alpha-macroglobulin.

Highly purified pancreatic secretory trypsin inhibitor (PSTI) from the dog was found to exist in three different chromatographic forms with equal capacities for the inhibition of trypsin. The molecular weight of the inhibitor, calculated from sodium dodecyl sulfate electrophoresis was approximately 7,000. It was capable of blocking proteolytic activity of trypsin-alpha-macroglobulin complex even though inhibition was never complete.