A comparison of the local environment of Cu(II) in native and half-Cu-depleted bovine serum amine oxidase

Electron spin-echo envelope modulation spectroscopy has been used to compare the local environment of Cu(II) in native bovine serum amine oxidase, containing two copper atoms/dimer molecule, and in a protein preparation, half depleted of copper, which has little enzymatic activity. For each preparation, two different populations of coordinated imidazoles with inequivalent magnetic coupling to copper could be recognized. In addition, water was shown to be a ligand to copper. No differences in coordinated ligand structures between the native and half-Cu-depleted preparations could be seen. In addition, the amount of ambient, non-coordinated water detected for native and half-Cu-depleted proteins was found to be nearly equivalent. However, the addition of phenylhydrazine, an inhibitor that binds to the pyrroloquinoline quinone cofactor but not to Cu(II) in the native enzyme, displaces ambient water near copper.