Structural Biology Laboratory, Department of Chemistry, University of York, York, YO31 7YD, UK.
Department of Molecular Biology and Biotechnology, Krebs Institute, University of Sheffield, Sheffield, S10 2TN, UK.
Top Curr Chem (Cham). 2017 Apr;375(2):36. doi: 10.1007/s41061-017-0130-y. Epub 2017 Mar 15.
The phosphoryl group, PO, is the dynamic structural unit in the biological chemistry of phosphorus. Its transfer from a donor to an acceptor atom, with oxygen much more prevalent than nitrogen, carbon, or sulfur, is at the core of a great majority of enzyme-catalyzed reactions involving phosphate esters, anhydrides, amidates, and phosphorothioates. The serendipitous discovery that the phosphoryl group could be labeled by "nuclear mutation," by substitution of PO by MgF or AlF, has underpinned the application of metal fluoride (MF ) complexes to mimic transition states for enzymatic phosphoryl transfer reactions, with sufficient stability for experimental analysis. Protein crystallography in the solid state and F NMR in solution have enabled direct observation of ternary and quaternary protein complexes embracing MF transition state models with precision. These studies have underpinned a radically new mechanistic approach to enzyme catalysis for a huge range of phosphoryl transfer processes, as varied as kinases, phosphatases, phosphomutases, and phosphohydrolases. The results, without exception, have endorsed trigonal bipyramidal geometry (tbp) for concerted, "in-line" stereochemistry of phosphoryl transfer. QM computations have established the validity of tbp MF complexes as reliable models for true transition states, delivering similar bond lengths, coordination to essential metal ions, and virtually identical hydrogen bond networks. The emergence of protein control of reactant orbital overlap between bond-forming species within enzyme transition states is a new challenging theme for wider exploration.
磷酸基（PO）是磷的生物化学中的动态结构单元。它从供体原子转移到受体原子，其中氧比氮、碳或硫更为普遍，这是涉及磷酸酯、酸酐、酰胺和硫代磷酸酯的绝大多数酶催化反应的核心。磷酸基可以通过“核突变”被标记，即通过用 MgF 或 AlF 取代 PO，这一偶然发现为金属氟化物（MF）配合物在模拟酶促磷酸转移反应的过渡态方面的应用提供了基础，这些配合物具有足够的稳定性以进行实验分析。固态蛋白质晶体学和溶液中的 F NMR 使直接观察包含 MF 过渡态模型的三元和四元蛋白质复合物成为可能，具有精确性。这些研究为一系列不同的磷酸转移过程（如激酶、磷酸酶、磷酸变位酶和磷酸水解酶）的酶催化提供了一种全新的、基于机制的方法。这些结果无一例外地支持了协同的、“直线型”磷酸转移立体化学的三角双锥几何形状（tbp）。QM 计算确立了 tbp MF 配合物作为真实过渡态可靠模型的有效性，提供了相似的键长、对必需金属离子的配位以及几乎相同的氢键网络。蛋白质控制酶过渡态中键形成物种之间反应物轨道重叠的出现，是一个新的具有挑战性的主题，需要更广泛的探索。
