ISOLATION AND CHARACTERIZATION OF A PROTEASE INHIBITOR FROM THE MARINE GASTROPOD TUGALI-GIGAS

A protease inhibitor, named tugalistatin, was isolated from the muscle of the marine gastropod Tugali gigas. Tugalistatin inhibited the prot eolytic activity of trypsin and alpha-chymotrypsin. It also suppressed the activity of kallikrein as well as elastase to some extent. On the other hand, it was inactive against metallo-proteases and cysteine pr oteases. These suggest that tugalistatin is a serine protease inhibito r. In SDS-polyacryamide gel electrophoresis it showed a single band co rresponding to 22,000 under reduced conditions. The molecular weight o f intact inhibitor was calculated to be 17,000 when checked by FPLC on a Superose 12 column. Amino acid analysis revealed tugalistatin conta ined a large amount of glutamic acid (14.0%), half-cystine (11.1%), an d aspartic acid (9.7%) in the molecule.