Diphosphonucleotide phosphatase/phosphodiesterase (PPD1) from yellow lupin (Lupinus luteus L.) contains an iron-manganese center

Yellow lupin diphosphonucleotide phosphatase/phosphodiesterase (PPD1) represents a novel group of enzymes. Here we report that it possesses one iron atom and one manganese atom (1:1 molar ratio) per subunit. The enzyme exhibits visible absorption maximum at ∼530 nm. Prolonged oxidation of PPD1 leads to loss of the charge-transfer band and catalytic activity, whereas after reduction PPD1 remains active. Replacement of conserved amino-acid residues coordinating metals results in the loss of enzymatic activity. Despite low amino-acid sequence homology of PPD1 to well-characterized ∼55-kDa purple acid phosphatases, their overall fold, topology of active center and metal content are highly similar.