Herschlag D, Jencks W P
Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254.
Biochemistry. 1990 May 29;29(21):5172-9. doi: 10.1021/bi00473a025.
The second-order rate constants for reaction of the Mg2+ complexes of phosphorylated pyridine monoanions with Mg(OH)+ are 10(4)-10(6)-fold larger than the second-order rate constants for their reaction with water (25 degrees C, ionic strength 1.5). Of the 10(6)-fold rate enhancement with the phosphorylated 4-morpholinopyridine/Mg2 complex, approximately 10(4)-fold is attributed to the greater nucleophilicity of Mg(OH)+ compared with water. The remaining catalysis of approximately 10(2)-fold is attributed to induced intramolecularity from positioning of the hydroxide ion and phosphoryl group by the Mg2+ ions. This reaction may provide a model for the role of a metal ion in increasing the concentration of the anions of enolpyruvate and serine and holding the nucleophile in the correct position for phosphoryl transfer in the reactions catalyzed by pyruvate kinase and alkaline phosphatase, for example. Some mechanisms that can provide catalysis of phosphoryl transfer through a metaphosphate-like transition state are reviewed briefly.
磷酸化吡啶单阴离子的Mg2+配合物与Mg(OH)+反应的二级速率常数比它们与水反应的二级速率常数大10(4)-10(6)倍（25℃，离子强度1.5）。在磷酸化4-吗啉吡啶/Mg2+配合物导致的10(6)倍速率增强中，约10(4)倍归因于Mg(OH)+相比于水具有更强的亲核性。其余约10(2)倍的催化作用归因于Mg2+离子使氢氧根离子和磷酰基定位从而诱导分子内作用。例如，该反应可能为金属离子在丙酮酸激酶和碱性磷酸酶催化的反应中增加烯醇丙酮酸和丝氨酸阴离子浓度并使亲核试剂处于磷酰基转移的正确位置所起的作用提供一个模型。简要综述了一些可通过类偏磷酸过渡态提供磷酰基转移催化作用的机制。
