A TRANSITION-STATE-ANALOG INHIBITOR INFLUENCES ZINC-BINDING BY AEROMONAS-AMINOPEPTIDASE

The transition-state-analog inhibitor, 1-butaneboronic acid, markedly enhances the uptake of one g-atom of Zn2+ ions from a metal ion buffer system by Zn-depleted Aeromonas aminopeptidase. In contrast, a substrate-analog inhibitor, n-valeramide, does not perturb the equilibrium between Zn2+ ions and the enzyme in a metal ion buffer system. These results establish a role for metal ions in the binding of 1-butaneboronic acid to Aeromonas aminopeptidase and strongly imply that a bound Zn2+ ion interacts directly with substrate during catalysis but not during initial binding of substrate.