Interaction of peptide boronic acids with elastase: Circular dichroism studies

Abstract

Boronic acid derivatives of good peptide substrates of the serine proteases cause slow-binding inhibition, manifested as biphasic binding (Kettner and Shenvi: J. Biol Chem. 259:15106-15114, 1984). These inhibitors are thought to act as reaction-intermediate analogs. Three peptide boronic acids--Ac-Pro-boro-Val-OH, DNS-Ala-Pro-boro-Val-OH, and Ac-Ala-Ala-Pro-boro-Val-OH--were chosen for far-ultraviolet circular dichroism (CD) studies in order to determine whether the second phase involves a conformational change of pancreatic elastase. The dipeptide is a simple competitive inhibitor (Ki = 0.27 microM) and the latter are slow-binding inhibitors (Ki = 16.4 and 0.25 nM, respectively). Spectral deconvolution and correction for the formation of antiparallel beta-sheet by the peptide inhibitor itself indicate that there is no significant change in the secondary structure of the enzyme in either the initial or final inhibitor complex. A kinetic experiment confirmed that the slow-binding step was not associated with a CD spectral change, and that therefore a protein conformational change was not responsible for the slow binding.

Dietary boron as a physiological regulator of the normal inflammatory response: A review and current research progress

“…Boron compounds are thought to reversibly inhibit the activity of serine proteases when the boron atom forms a tetrahedral boron adduct that mimics the tetrahedral adduct formed during normal substrate hydrolysis [32][33][34]. This phenomenon has been studied with substituted boric acid compounds (e.g., arylboronic acids).…”

Boron in plants and animals: Is there a role beyond cell‐wall structure?

“…Serine proteases are major proteolytic enzymes and have, in addition to degrading struc-tural proteins, regulatory roles in normal inflammation processes . In serine proteases, the B atom is thought to inhibit the formation of a tetrahedral B adduct (the transition-state analog) that mimics the tetrahedral adduct formed during normal substrate hydrolysis (Berry et al, 1988). The adduct includes a covalent bond between B and a specific N at the active site of these enzymes.…”

Dietary boron: An overview of the evidence for its role in immune function

“…The serine proteases are major proteolytic enzymes (i.e., elastase, chymase, and cathepsin G) released by activated leukocytes that, in addition to degrading structural proteins, have many essential regulatory roles in normal inflammation, including control of the blood fibrinolytic system (e.g., thrombin) and the coagulation system (e.g., coagulation Factor Xa) [59]. The boron atom is thought to inhibit the serine proteases by forming a tetrahedral B adduct (the transition-state analog) that mimics the tetrahedral adduct formed during normal substrate hydrolysis [60]. The adduct includes a covalent bond between boron and a specific nitrogen at the active site of these enzymes (Structure 5).…”