Amino acid sequence determination and biological activity of therin, a naturally occuring specific trypsin inhibitor from the leech Theromyzon tessulatum

Eur J Biochem. 1998 Jun 15;254(3):565-70. doi: 10.1046/j.1432-1327.1998.2540565.x.


We purified a trypsin inhibitor, designated therin, from the rhynchobdellid leech Theromyzon tessulatum. Therin was purified to apparent homogeneity by gel-permeation and anion-exchange chromatography followed by reverse-phase HPLC. By a combination of reduction and S-beta-pyridylethylation, Edman degradation and electrospray mass spectrometry measurement, the complete sequence of therin (48 amino acid residues; m/z, 5376.35 +/- 0.22 Da) was determined. Therin exhibits an approximately 30% sequence similarity with peptides of the antistasin-type inhibitors family, i.e. the first and second domains of antistasin, hirustasin, ghilanthen and guamerins (I, II). Therin is a tight-binding inhibitor of trypsin (Ki, 45 +/- 12 pM) and has no action towards elastase or cathepsin G. Furthermore, therin (10(-6) M) in conjunction with theromin, a Theromyzon thrombin inhibitor (10(-6) M) significantly diminish the level of human leucocytes activation induced by lipopolysaccharide (10 microg) in a manner similar to that of aprotinin. These data suggest a leech trypsin inhibitor with possible biomedical significance.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adjuvants, Immunologic / pharmacology
  • Amino Acid Sequence
  • Animals
  • Cells, Cultured
  • Chromatography, Gel
  • Chromatography, High Pressure Liquid
  • Chromatography, Ion Exchange
  • Humans
  • Leeches / chemistry*
  • Leukocytes / drug effects
  • Molecular Sequence Data
  • Oligopeptides / chemistry*
  • Oligopeptides / isolation & purification
  • Oligopeptides / pharmacology
  • Trypsin Inhibitors / chemistry*
  • Trypsin Inhibitors / pharmacology


  • Adjuvants, Immunologic
  • Oligopeptides
  • Trypsin Inhibitors
  • therin