Mössbauer and EPR study of the binuclear iron centre in purple acid phosphatase

Mössbauer spectra have been determined on 57Fe-enriched samples of both pink (reduced) and purple (oxidized) forms of pig allantoic acid phosphatase (EC 3.1.3.2), and EPR spectra on corresponding unenriched samples. The spectra show unambiguously that both forms of the enzyme contain two distinct, antiferromagnetically coupled, high-spin iron atoms: a ferrous-ferric ion pair in the pink, reduced form, and a pair of ferric ions in the purple, oxidized form.