Interaction of peptide boronic acids with elastase: circular dichroism studies.
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.
Berry
S C
SC
Department of Chemistry, University of California, Santa Cruz 95064.
Fink
A L
AL
Shenvi
A B
AB
Kettner
C A
CA
D000818:Animals; D001897:Boronic Acids; D002942:Circular Dichroism; D004735:Energy Transfer; D007700:Kinetics; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors; D010455:Peptides; D011487:Protein Conformation; D013379:Substrate Specificity; D013552:Swine
D001897:Boronic Acids; D010455:Peptides; D010196:Pancreatic Elastase