ELECTRON-PARAMAGNETIC-RESONANCE STUDIES OF COBALT-SUBSTITUTED ANGIOTENSIN I-CONVERTING ENZYME

Electron paramagnetic resonance (EPR) spectroscopy has been used to st udy the metal coordination sphere geometry in the cobalt-substituted Z n-protein angiotensin I-converting enzyme (ACE). It has been shown tha t ACE contains two distinct metal-binding sites. In the presence of th e two structurally different inhibitors, captopril and ramiprilat, it is found that the metal binding sites are nearly structurally identica l and are separated more than 10 Angstrom from each other. The metal a toms are most likely four- to five-coordinated, and it is argued that the inhibitor binds directly to the metal ion.