EXAFS Studies on Pig Plasma Amine Oxidase. A Detailed Structural Analysis Using the Curved Wave Multiple Scattering Approach

EXAFS studies have been carried out on pig plasma amine oxidase containing one copper and two copper atoms. The data for the two forms are essentially identical and are consistent with the presence of four low-Z scatterers and one heavier scatterer in the primary ligand shell. There is evidence that the heavy scatterer is a sulfur atom coordinated at 2.38 A. The four low-Z scatterers distribute themselves about the copper atom at two discrete distances, 2.00 and 1.90 A. The 2.00-A distance is accounted for by two nitrogens and the outer shell analysis is consistent with this as imidazole coordination. The two low-Z scatterers at 1.90 A are consistent with Cu-0 coordination, probably arising from phenolate and/or OH^-. The analysis provides no direct evidence for or against the presence of PQQ coordinated to copper.