X-ray absorption studies of the purple acid phosphatase from beef spleen
X-ray absorption studies of the purple acid phosphatase from beef spleen
复制标题
牛脾紫色酸性磷酸酶的X射线吸收研究
DOI：
10.1021/ic00236a025
复制
发表时间：
1986
影响因子：
4.6
通讯作者：
B. Averill
中科院分区：
文献类型：
--
作者：
S. Kauzlarich;B. Teo;T. Zirino;S. Burman;J. Davis;B. Averill
Iron K-edge near-edge (XANES) and extended X-ray absorption fine structure (EXAFS) spectra have been measured for the purple acid phosphatase from beef spleen and for several oxo-bridged model complexes. The XANES show a shift of the absorption edge to lower energy by 2.0 eV upon reduction of the purple form of the enzyme to the pink form, consistent with reduction of one of the iron atoms. Fourier transforms of the EXAFS data of the purpleform of the enzyme show three peaks, assigned to Fe-O (N)(first shell), Fe--Fe and Fe--P or Fe--C (second shell), and Fe--C (N)(imidazole, third shell) scatterers, in order of increasing distance. Best fits of the individually back-transformed peaks using theoretical functions are consistent with the indicated assignments. The Fe--Fe distance of 3.00 A is consistent with a bridged binuclear iron center in the enzyme. Due to the presence of short Fe-O (tyrosine) linkages at 1.8-1.9 A, direct evidence for a bridging oxo group at ca. 1.8 A could notbe obtained. The observed Fe--P distance of 3.06 A is most consistent with the presence of a phosphate as a monodentate ligand to one iron atom in the purple (oxidized) form of the enzyme.Purple acid phosphatases are characterized by their intense (e~ 4000 M" 1 cm-1) absorption band at 510-550 nm. 5 Their presence in mammalian, plant, and microbial sources5, 63 suggests that these enzymes are of primary importance in the regulation of the physiological level of inorganic phosphate and phospho-
