Purple acid phosphatase from bovine spleen. Interactions at the active site in relation to the reaction mechanism.

摘要: Oxidation of the reduced (pink) phosphate-free bovine spleen acid phosphatase with 1.5 mol H2O2 or sodium peroxodisulfate/mol, in presence Mes Bistris pH 5, leads to a species an absorption maximum at 558 nm. Addition acetate oxidation buffer engenders 550 phosphate both shifts immediately 540 nm; this is also found after preparation from spleen. The assumption that these represent strongly bidentate-binding hydroxo, acetato and phosphato complexes Fe(III)-Fe(III) system supported by replacement reactions other ligating oxoanions followed their typical spectral shifts. These oxoanion cannot be dissociated gel filtration; possible only reduction Fe(II)-Fe(III) system. oxidized without EPR signals below g values 2 still reveals 5% activity which zero even higher concentrations peroxodisulfate. optimum reaction alpha-naphthyl 5.9 5.3 species. apparent pK around 4.5 as derived dependence activity, spectra, phosphate-saturated are assigned aquo/hydroxo equilibrium Fe(III) equilibrium, where ligand replaced hydroxo ligand. A mechanism proposed chromophoric attacks phosphoric ester group when monoprotonated pre-oriented electrostatic interaction nonchromophoric metal ion. Binding inhibition studies indicate they compete catalytically active enzyme nearly same constants. Catalysis not affected replace additional mu-hydroxo 558-nm-absorbing In contrast hemerythrin ribonucleotide reductase, binuclear iron center for purple phosphatase, bridged carboxylato two groups, but mu-oxo bridge.