Isolation and amino acid sequence of two trypsin isoinhibitors from duck pancreas

DPTI II and DPTI IV, two trypsin inhibitors from duck pancreas, have been i solated by affinity chromatography on immobilized anhydrotrypsin, anion exc hange and RP-HPLC. The complete amino acid sequence of both inhibitors was determined after reductive carboxymethylation and digestion with Staphyloco ccus aureus V8 protease or trypsin. The inhibitors were each found to be a single polypeptide chain comprised of 69 amino acid residues and their mole cular masses were estimated at 7687 Da for DPTI II and 7668 Da for DPTI IV. The only difference in amino acid sequence between the two inhibitors is t he replacement of Arg for His residue in the C-terminal position of DPTI IV . (C) 1999 Elsevier Science Inc. All rights reserved.