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

Publisher Website
Google Scholar
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°C to 40°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] > human leucocyte elastase ⋍ human cathepsin G ⋍ subtilisin Carlsberg ⋍ bovine α‐chymotrypsin > bovine α‐chymotrypsinogen A ⋍ porcine pancreatic elastase ⋍ bovine β‐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 to the invariant hystidyl catalytic residue from ≈︁ 6.9 in the free serine proteinases and bovine α‐chymotrypsinogen A 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.