The interaction of phosphate with uteroferrin. Characterization of a reduced uteroferrin-phosphate complex.

Evidence for Nonbridged Coordination of p-Nitrophenyl Phosphate to the Dinuclear Fe(III)−M(II) Center in Bovine Spleen Purple Acid Phosphatase during Enzymatic Turnover

“…These discrepancies may be due to the differences in isolation procedure for BSPAP employed (the present study uses the so-called high-salt form of BSPAP (12), which is more stable and has a more ordered secondary structure than the low-salt form studied by Dietrich et al (11)). pHdependent shifts in the absorption maxima (λ max ) of the phosphate complexes of PAPs have been reported in several other studies (5,11,12,47). Pyrz et al observed similar pH-dependent changes in the optical spectra of FeFe-Uf-PO 4 as well as pH-dependent inhibition constants for phosphate, with an apparent pK a of 5 (5).…”

“…In the absence of a good nonhydrolyzable substrate analogue, phosphate has been assumed to mimic the binding mode of the phosphate ester substrate, although it is actually one of the products of the reaction. Phosphate has been reported to be a competitive (Uf, pH 5) (5,38) or mixedtype inhibitor (BSPAP, pH 6) (12) with an affinity similar to that for substrate. Several spectroscopic studies have provided evidence that phosphate binds to both metal ions in a bridging coordination mode.…”

“…As indicated, these studies were performed at pH e5, as have been most other spectroscopic studies on PAPs. Other groups have reported pH-dependent changes in the spectral properties of the phosphate complex (5,11) and suggested a bridging phosphate coordination at low pH and end-on binding to the divalent metal ion (Fe 2+ or Zn 2+ ) at higher pH (11). No systematic study has thus far been reported that correlates these pH dependent changes in spectral properties of the phosphate complex with the pH dependent changes in kinetics parameters, most importantly the pH dependence of k cat .…”

Hydrolysis of glucose-6-phosphate in aged, acid-forced hydrolysed nanomolar inorganic iron solutions—an inorganic biocatalyst?

“…It is interesting to compare the catalytic behavior of aged iron solution to natural phosphoesterase and their biomimetic, though the velocities of hydrolysis G6P in aged iron solutions are much lower than that of phosphoesterase. For natural phosphoesterase, K m and K i of PO 4 is usually in the millimolar range; [55][56][57][58][59][60] only K i of WO 4 and MoO 4 is in the micromolar range. 57,58,[61][62][63] The value of K m of G6P is 920 mM for phosphoesterase extracted from sweet potato 50 and 300-310 mM for those from soybean seed.…”

Mechanism of the reaction of different phosphates with the iron(II)iron(III) form of purple acid phosphatase from porcine uteri (uteroferrin)

“…Isolutiun of PAP ( Uteroferrin).-Uteroferrin was obtained from the allantoic fluid of a sow at mid-pregnancy, and purified according to a literature procedure. 18 The product isolated consists of about equal amounts of active and inactive PAP, and PAP,, the latter with phosphate bound. The PAP, protein was reduced to the Fe'IFe"' state with 0.1 M ascorbate and 6 mM ammonium iron(I1) sulfate in 0.05 M acetate buffer at pH 5.0.…”