Interaction of peptide boronic acids with elastase: Circular dichroism studies

✍ Scribed by S. C. Berry; Anthony L. Fink; A. B. Shenvi; C. A. Kettner

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: English
• Weight: 594 KB
• Volume: 4
• Category: Article
• ISSN: 0887-3585
• DOI: 10.1002/prot.340040307

✦ Synopsis

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.