American Society of Hirudotherapy

Binding of the recombinant proteinase inhibitor eglin c from leech Hirudo medicinalis to serine (pro)enzymes: a comparative thermodynamic study

Biochemistry article published in Journal of Molecular Recognition (1991)

Last Updated: June 18, 2026Reviewed by: ASH Editorial Board
Research article — evidence reviewArticle reference
Evidence: Observational studySalivary PharmacologyAscenzi P, Aducci P, Amiconi G et al. · Journal of molecular recognition, 1991

Abstract

The binding of the recombinant proteinase inhibitor eglin c from the leech Hirudo medicinalis to serine (pro)enzymes belonging to the chymotrypsin and subtilisin families has been investigated from the thermodynamic viewpoint, between pH 4.5 and 9.5 and from 10 degrees C to 40 degrees C. The affinity of eglin c for the serine (pro)enzymes considered shows the following trend: Leu-proteinase [the leucine specific serine proteinase from spinach (Spinacia oleracea L.) leaves] greater than human leucocyte elastase congruent to human cathepsin G congruent to subtilisin Carlsberg congruent to bovine alpha-chymotrypsin greater than bovine alpha-chymotrypsinogen A congruent to porcine pancreatic elastase congruent to bovine beta-trypsin. The serine (pro)enzyme-inhibitor complex formation is an entropy-driven process. On increasing the pH from 4.5 to 9.5, the affinity of eglin c for the serine (pro)enzymes considered increases thus reflecting the acid pK shift of the invariant hystidyl catalytic residue from approximately to 6.9 in the free serine proteinases and bovine alpha-chymotrypsinogen A to congruent to 5.1 in the serine (pro)enzyme-inhibitor complexes. Considering the known molecular models, the observed binding behaviour of eglin c was related to the inferred stereochemistry of the serine (pro)enzyme-inhibitor contact regions.

Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.

Publication typeComparative StudyJournal ArticleResearch Support, Non-U.S. Gov't
Indexed MeSH termsAnimalsEnzyme PrecursorsHumansHydrogen-Ion ConcentrationIn Vitro TechniquesLeechesProteinsSerineSerine Proteinase InhibitorsSerpinsThermodynamics

Summary

Comparative pH- and temperature-dependent thermodynamics of leech eglin C binding to multiple serine (pro)enzymes (cathepsin G, leukocyte elastase, chymotrypsin, subtilisin) reveal entropy-driven binding with affinity governed by catalytic histidine pKa shifts.

Why This Matters for Hirudotherapy

This work conducted a comparative thermodynamic investigation of the binding of recombinant eglin c from Hirudo medicinalis to serine (pro)enzymes of the chymotrypsin and subtilisin families, measuring affinity across pH 4.5-9.5 and 10-40 °C. Affinity followed the trend Leu-proteinase > human leucocyte elastase ≈ human cathepsin G ≈ subtilisin Carlsberg ≈ bovine alpha-chymotrypsin > several zymogens and trypsins, with complex formation being entropy-driven and affinity increasing with pH due to a catalytic-histidyl pK shift. For ASH's domain, this deepens understanding of how a leech-secretome serine-proteinase inhibitor engages its targets. Caveat: this is a purely in-vitro thermodynamic/biophysical characterization with no therapeutic, in-vivo, or hirudotherapy data.

Citation

Binding of the recombinant proteinase inhibitor eglin c from leech Hirudo medicinalis to serine (pro)enzymes: a comparative thermodynamic study.

Ascenzi P, Aducci P, Amiconi G et al. · Journal of molecular recognition, 1991

DOI

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