A New Trypsin Inhibitor from Hirudo nipponia

Abstract

A new trypsin inhibitor, bdellin for Korean leech (bdellin-KL), was isolated from a blood sucking leech, Hirudo nipponia. It has a molecular mass of 16156.4 Da and pi value of 4.0. The inhibitor was stable at a range of pH 1.3 through 10.0 and temperatures ranging from 20 degrees C to 90 degrees C. The bdellin-KL showed inhibition constants of 1.67 +/- 0.73 x 10(-9) M for trypsin and 1.76 +/- 1.29 x 10(-9) M for plasmin but a poor activity against chymotrypsin. Over 60 amino acid residues of the N-terminal region showed a high similarity with those of the high-molecular mass bdellin B-3 (HMB), a European leech-derived trypsin-plasmin inhibitor. The first 10 residues that contained a P1 reactive site of Lys and the spacing of six cysteines in the peptide are well conserved for the two phylogenetically different species.