Purification and characterization of pancreatic secretory trypsin inhibitor in human gastric mucosa.

Immunoreactive pancreatic secretory trypsin inhibitor (PSTI) was purified to homogeneity from human gastric mucosa by gel chromatography, ion-exchange chromatography, and repeated reverse-phase high-performance liquid chromatography (HPLC). The molecular weight of the purified immunoreactive PSTI in human gastric mucosa was estimated to be 6000. The electrophoretical mobility of purified PSTI was identical with that of the main component of PSTI in human pancreatic juice. It consisted of 56 amino acids and had the same amino acid composition as PSTI in pancreatic juice. It inhibited bovine pancreatic trypsin stoichiometrically, and did not inhibit porcine pancreatic kallikrein or elastase. Heat treatment of immunoreactive PSTI in gastric mucosa showed the same inactivation curve of immunoreactivity as that of pancreatic juice PSTI.