Characterization and N-terminal sequence of a degradation product of 14,000 molecular weight isolated from human pancreatic juice.

Chromatography of human pancreatic juice has allowed the isolation of an inactive protein of 14,000 Mr (protein X) and the determination of its amino acid composition and N-terminal sequence. Protein X was found to be immunologically identical to the protein extracted from precipitates present in the pancreatic juices of patients with chronic calcifying pancreatitis and recently shown to be a degradation product of trypsinogen 1. The same chromatography performed in the presence of lima bean trypsin inhibitor has permitted the isolation of precursors of approximately congruent to 19,000 Mr which can be transformed into protein X "in vitro" by chymotrypsin hydrolysis. These results emphasize the easy activation of human pancreatic zymogens and the possible consequences due to proteolysis in pancreatic disease.