Flight of a Cytidine Deaminase Complex with an Imperfect Transition State Analogue Inhibitor: Mass Spectrometric Evidence for the Presence of a Trapped Water Molecule
作者:Gottfried K. Schroeder、Li Zhou、Mark J. Snider、Xian Chen、Richard Wolfenden
DOI:10.1021/bi300516u
日期:2012.8.14
masses of E2Zn2W2 (dimeric Zn-CDA with two water molecules), E2Zn2W2Fz, and E2Zn2W2Fz2, where Fz represents the 3,4-hydrate of 5-fluorozebularine. In the absence of an inhibitor, E2Zn2 is the only dimeric species detected, with no additional water molecules. Experiments conducted in H218O indicate that the added mass W represents a trapped water molecule rather than an isobaric ammonium ion. This appears
胞苷脱氨酶(CDA)结合抑制剂zebularine作为其3,4-水合物(ķ d〜10 -12 M),捕捉所有但结合预期的理想过渡态类似物的自由能的~5.6千卡/摩尔(ķ TX〜10 –16 M)。根据其熵的起源,这种短缺暂时归因于水分子滞留在酶抑制剂复合物中,正如先前在尿苷产品中所观察到的那样[Snider,MJ,and Wolfenden,R.(2001)Biochemistry 40,11364-11371]。在饱和5-氟泽布来碱饱和下成核的CDA的傅里叶变换离子回旋共振质谱(FTICR-MS)揭示了与E 2的质量相对应的峰Zn 2 W 2(具有两个水分子的二聚体Zn-CDA),E 2 Zn 2 W 2 Fz和E 2 Zn 2 W 2 Fz 2,其中Fz代表5-氟泽布来碱的3,4-水合物。在没有抑制剂的情况下,E 2 Zn 2是唯一检测到的二聚体,没有其他水分子。在H 2 18中进行的