The different iron binding sites of bovine spleen purple acid phosphatase

The purple acid phosphatase contains two inequivalent irons which can be removed subsequently. The Mossbauer spectrum of the purple inactive enzyme (oxidized) indicates two high spin ferric irons with antiparallel coupling giving zero effective spin. The active pink enzyme (partly reduced) is obtained by a one electron transfer to the iron which is less stable bound in the protein. The Mossbauer spectra indicate a high spin Fe(2+) antiparallel spin coupled to high spin Fe(3+).