Evidence for a conserved binding motif of the dinuclear metal site in mammalian and plant purple acid phosphatases: H-1 NMR studies of the di-iron derivative of the Fe(III)Zn(II) enzyme from kidney bean

The di-iron core of mammalian purple acid phosphatases has been reproduced in the plant enzyme from kidney bean (M-r 111 000) upon insertion of an Fe(II) ion in place of the native zinc(II) in the dinuclear Fe(III)/Zn(II) core. The shortening of the electronic relaxation time of the metal centre allows detection of hyperfine-shifted H-1 NMR resonances, although severe broadening due to Curie relaxation prevents independent signal assignment. Nevertheless, comparison of the spectral features of the structurally characterized plant enzyme with those of the mammalian species, which were previously extensively assigned, is consistent with a close similarity of the metal-binding sites, also suggested by previous sequence-alignment studies. Some differences appear to be mainly localized at the M(II) site. Spectral comparison was also carried out on the Fe(III)Co(II) derivatives.