Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27514, USA.
J Am Chem Soc. 2009 Dec 30;131(51):18248-9. doi: 10.1021/ja907967y.
The hydrolysis of simple phosphate monoesters is among the most difficult reactions that are subject to catalysis by enzymes, and it has been suggested that extraction of the substrates from solvent water may contribute to the catalytic effects of phosphohydrolases. Here, we show that the tetrabutylammonium salt of neopentyl phosphate enters wet cyclohexane at concentrations sufficient to allow determination of its rate of hydrolysis. The second-order rate constant for hydrolysis of the phosphomonoester dianion is enhanced approximately 2 x 10(12)-fold by transfer from water to cyclohexane. That rate enhancement arises from an increase in the entropy of activation.
简单的磷酸单酯的水解是最难以被酶催化的反应之一，有人提出，从溶剂水中提取底物可能有助于磷酸水解酶的催化作用。在这里，我们表明新戊基磷酸的四丁基铵盐以足以允许测定其水解速率的浓度进入湿环己烷。磷酸单酯二阴离子的水解的二级反应速率常数通过从水到环己烷的转移被增强了约 2 x 10(12)倍。这种速率增强来自于活化熵的增加。
