Anion Binding to Porcine Pancreatic α-Amylase as Probed by Bromine-81 Nuclear Magnetic Resonance Spectrometry

A bromine-81 NMR study was conducted to characterize the Cl − -binding site of porcine pancreatic α-amylase. Only a single signal was observed in the spectrum in the presence of an equimolar concentration of the enzyme and NaBr. the signal was assigned to free Br ions, which are in very slow exchange with the protein-bound Br on an NMR time scale. the presence of a common anion-binding site was demonstrated from the competition of Br with F − , Cl − , NO − 3 , and ClO − 4 for the site.