Binding of the recombinant proteinase inhibitor eglin c from leech hzrudo medzcznalzs to human leukocyte elastase, bovine αchymotrypsin and subtilisin carlsberg: Thermodynamic study

Paolo Ascenzi, Gino Amiconi, Enea Menegatti, Mario Guarneri, Martino Bolognesi, Hans Peter Schnebli

Research output: Contribution to journalArticle

Abstract

The effect of pH and temperature on the apparent association equilibrium constant (Ka) for the binding of the recombinant proteinase inhibitor eglin c from leech Hirudo medicinalis to human leukocyte elastase (EC 3.4.21.37), bovine αchymotrypsin (EC 3.4.21.1) and subtilisin Carlsberg (EC 3.4.21.14) has been investigated. On lowering the pH from 9.5 to 4.5, values of Ka for eglin c binding to the serine proteinases considered decrease thus reflecting the acid-pK shift of the invariant histidyl catalytic residue (His57 in human leukocyte elastase and bovine αchymotrypsin, and His64 in subtilisin Carlsberg) from ∼ 6.9, in the free enzymes, to ∼ 5.1, in the enzyme inhibitor adducts. At pH 8.0, values of the apparent thermodynamic parameters for eglin c binding are: human leukocyte elastase - Ka == 1.0 ∼ 1010M-1, δGφS == - 13.4 kcal/mol, δHφS == + 1.8 kcal/mol, and δSφS == + 52 entropy units; bovine αchymotrypsin - Ka == 5.0 ∼ 109 M-1, δGφS == -13.0 kcal/mol, δHφS == + 2.0 kcal/mol, and δSφS == + 51 entropy units; and subtilisin Carlsberg - Ka == 6.6 ∼ 109M-1. δGφS == -13.1 kcal/mol, δHφS == +2.0 kcal/mol, and δSφS == +51 entropy units (values of Ka, δGφS and δSφS were obtained at 21∼C; values of δHφS were temperature independent over the range explored, i.e. between 10∼C and 40∼C; I kcal == 4184 J). Thermodynamics of eglin c binding to the serine proteinases considered has been analyzed in parallel with those of related (pro)enzyme:macromolecular inhibitor systems. Considering the known molecular models, the observed binding behaviour of eglin c was related to the inferred stereochemistry of the proteinase:inhibitor contact regions.

Original languageEnglish
Pages (from-to)167-172
Number of pages6
JournalJournal of Enzyme Inhibition and Medicinal Chemistry
Volume2
Issue number3
DOIs
Publication statusPublished - 1988

Keywords

  • Bovine αchymotrypsin
  • Enzyme
  • Human leukocyte elastase
  • Inhibitor adduct formation
  • PH effects (on enzyme: inhibitor adduct formation)
  • Recombinant proteinase inhibitor eglin c (from leech Hirudo medicinalis)
  • Subtilisin Carlsberg
  • Thermodynamics (of enzyme:inhibitor complex formation)

ASJC Scopus subject areas

  • Drug Discovery
  • Pharmacology
  • Biochemistry
  • Molecular Medicine

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