Bruice Thomas C
Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA.
Acc Chem Res. 2002 Mar;35(3):139-48. doi: 10.1021/ar0001665.
Binding TS in preference to S and increasing TDeltaS++by freezing out motions in E X S and E X TS have been accepted as the driving forces in enzymatic catalysis; however, the smaller value of DeltaG++ for a one-substrate enzymatic reaction, as compared to its nonenzymatic counterpart, is generally the result of a smaller value of DeltaH++. Ground-state conformers (E X NACs) are formed in enzymatic reactions that structurally resemble E X TS. E X NACs are in thermal equilibrium with all other E X S conformers and are turnstiles through which substrate molecules must pass to arrive at the lowest-energy TS. TS in E X TS may or may not be bound tighter than NAC in E X NAC.
优先结合过渡态（TS）而非底物（S），并通过限制酶-底物复合物（E X S）和酶-过渡态复合物（E X TS）中的运动来增加过渡态熵增量（TDeltaS++），这已被公认为酶催化的驱动力；然而，与非酶促反应相比，单底物酶促反应的活化自由能（DeltaG++）较小，通常是由于活化焓（DeltaH++）较小。在酶促反应中会形成基态构象体（E X NACs），其结构类似于E X TS。E X NACs与所有其他E X S构象体处于热平衡状态，并且是底物分子必须通过才能到达最低能量过渡态的旋转门。E X TS中的过渡态与E X NACs中的基态构象体相比，结合可能更紧密，也可能不更紧密。
