Acid- and heat-stable trypsin inhibitory peptide from the viscera of japanese common squid (todarodes pacificus)

Trypsin inhibitor was purified from the viscera except for the hepatopancreas of Japanese common squid (Todarodes pacificus) by gel filtration and anion-exchange chromatography. Final inhibitor preparation was homogeneous as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and its molecular weight was estimated to be approximately 6,000 Da. The N-terminal amino acid sequence of the squid trypsin inhibitor was determined as ANEATXVYKGKTYKKGEGF. The purified inhibitor was heat stable up to 150 min at 80C at pH 8.0. The inhibitory activity was also retained at pH 2.0 and 37C for 180 min. The squid trypsin inhibitor was active against walleye pollock trypsin as well as porcine pancreatic trypsin. The squid trypsin inhibitor showed hypoglycemic effect on blood glucose levels of GK rats, a model of type 2 diabetes.