Feierberg I, Cameron A D, Aqvist J
Department of Cell and Molecular Biology, Uppsala University, Sweden.
FEBS Lett. 1999 Jun 18;453(1-2):90-4. doi: 10.1016/s0014-5793(99)00703-6.
The proposed rate-limiting step of the reaction catalyzed by glyoxalase I is the proton abstraction from the C1 carbon atom of the substrate by a glutamate residue, resulting in a high-energy enolate intermediate. This proton transfer reaction was modelled using molecular dynamics and free energy perturbation simulations, with the empirical valence bond method describing the potential energy surface of the system. The calculated rate constant for the reaction is approximately 300-1500 s(-1) with Zn2+, Mg2+ or Ca2+ bound to the active site, which agrees well with observed kinetics of the enzyme. Furthermore, the results imply that the origin of the catalytic rate enhancement is mainly associated with enolate stabilization by the metal ion.
乙二醛酶I催化反应中提出的限速步骤是谷氨酸残基从底物的C1碳原子夺取质子，从而产生高能烯醇化物中间体。该质子转移反应通过分子动力学和自由能微扰模拟进行建模，采用经验价键方法描述系统的势能面。当活性位点结合Zn2+、Mg2+或Ca2+时，计算得到的反应速率常数约为300 - 1500 s(-1)，这与观察到的该酶动力学结果吻合良好。此外，结果表明催化速率提高的根源主要与金属离子对烯醇化物的稳定作用有关。
