Apparent NAC Effect in Chorismate Mutase Reflects Electrostatic Transition State Stabilization

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• 作者：Marek //pubs.acs.org/images/entities/Scaron.gif" border="0">trajbl ; Avital Shurki ; Mitsunori Kato ; and Arieh Warshel
• 刊名：Journal of the American Chemical Society
• 出版年：2003
• 出版时间：August 27, 2003
• 年：2003
• 卷：125
• 期：34
• 页码：10228 - 10237
• 全文大小：225K
• 年卷期：v.125,no.34(August 27, 2003)
• ISSN：1520-5126

文摘

The catalytic reaction of chorismate mutase (CM) has been the subject of major current attention.Nevertheless, the origin of the catalytic power of CM remains an open question. In particular, it has notbeen clear whether the enzyme works by providing electrostatic transition state stabilization (TSS), byapplying steric strain, or by populating near attack conformation (NAC). The present work explores thisissue by a systematic quantitative analysis. The overall catalytic effect is reproduced by the empirical valencebond (EVB) method. In addition, the binding free energy of the ground state and the transition state isevaluated, demonstrating that the enzyme works by TSS. Furthermore, the evaluation of the electrostaticcontribution to the reduction of the activation energy establishes that the TSS results from electrostaticeffects. It is also found that the apparent NAC effect is not the reason for the catalytic effect but the resultof the TSS. It is concluded that in CM as in other enzymes the key catalytic effect is electrostatic TSS.However, since the charge distribution of the transition state and the reactant state is similar, the stabilizationof the transition state leads to reduction in the distance between the reacting atoms in the reactant state.