Lahiri Sushmita D, Zhang Guofeng, Dunaway-Mariano Debra, Allen Karen N
Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118-2394, USA.
Science. 2003 Mar 28;299(5615):2067-71. doi: 10.1126/science.1082710. Epub 2003 Mar 13.
Enzymes provide enormous rate enhancements, unmatched by any other type of catalyst. The stabilization of high-energy states along the reaction coordinate is the crux of the catalytic power of enzymes. We report the atomic-resolution structure of a high-energy reaction intermediate stabilized in the active site of an enzyme. Crystallization of phosphorylated beta-phosphoglucomutase in the presence of the Mg(II) cofactor and either of the substrates glucose 1-phosphate or glucose 6-phosphate produced crystals of the enzyme-Mg(II)-glucose 1,6-(bis)phosphate complex, which diffracted x-rays to 1.2 and 1.4 angstroms, respectively. The structure reveals a stabilized pentacovalent phosphorane formed in the phosphoryl transfer from the C(1)O of glucose 1,6-(bis)phosphate to the nucleophilic Asp8 carboxylate.
酶能极大地提高反应速率，这是其他任何类型的催化剂都无法比拟的。沿着反应坐标对高能态的稳定作用是酶催化能力的关键所在。我们报道了一种在酶活性位点稳定存在的高能反应中间体的原子分辨率结构。在Mg(II)辅因子以及底物葡萄糖1-磷酸或葡萄糖6-磷酸存在的情况下，磷酸化β-磷酸葡萄糖变位酶结晶形成了酶-Mg(II)-葡萄糖1,6-(双)磷酸复合物晶体，其X射线衍射分辨率分别达到1.2埃和1.4埃。该结构揭示了在从葡萄糖1,6-(双)磷酸的C(1)O向亲核性天冬氨酸8羧酸盐的磷酰基转移过程中形成的一种稳定的五价磷烷。
