An Approach to More Accurate Model Systems for Purple Acid Phosphatases (PAPs)

详细信息    查看全文

• 作者：Paul V. Bernhardt ; Simone Bosch ; Peter Comba ; Lawrence R. Gahan ; Graeme R. Hanson ; Valeriu Mereacre ; Christopher J. Noble ; Annie K. Powell ; Gerhard Schenk ; Hubert Wadepohl
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：August 3, 2015
• 年：2015
• 卷：54
• 期：15
• 页码：7249-7263
• 全文大小：770K
• ISSN：1520-510X

文摘

The active site of mammalian purple acid phosphatases (PAPs) have a dinuclear iron site in two accessible oxidation states (Fe^III₂ and Fe^IIIFe^II), and the heterovalent is the active form, involved in the regulation of phosphate and phosphorylated metabolite levels in a wide range of organisms. Therefore, two sites with different coordination geometries to stabilize the heterovalent active form and, in addition, with hydrogen bond donors to enable the fixation of the substrate and release of the product, are believed to be required for catalytically competent model systems. Two ligands and their dinuclear iron complexes have been studied in detail. The solid-state structures and properties, studied by X-ray crystallography, magnetism, and M枚ssbauer spectroscopy, and the solution structural and electronic properties, investigated by mass spectrometry, electronic, nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and M枚ssbauer spectroscopies and electrochemistry, are discussed in detail in order to understand the structures and relative stabilities in solution. In particular, with one of the ligands, a heterovalent Fe^IIIFe^II species has been produced by chemical oxidation of the Fe^II₂ precursor. The phosphatase reactivities of the complexes, in particular, also of the heterovalent complex, are reported. These studies include pH-dependent as well as substrate concentration dependent studies, leading to pH profiles, catalytic efficiencies and turnover numbers, and indicate that the heterovalent diiron complex discussed here is an accurate PAP model system.