关于多金属氧酸盐催化ATP水解的31P核磁共振和等温滴定量热法研究。

31P NMR and isothermal titration calorimetry studies on polyoxomolybdates-catalyzed hydrolysis of ATP.

作者信息

Ishikawa Eri, Yamase Toshihiro

机构信息

Chemical Resources Laboratory, Tokyo Institute of Technology, R1-21, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.

出版信息

J Inorg Biochem. 2006 Mar;100(3):344-50. doi: 10.1016/j.jinorgbio.2005.11.021. Epub 2006 Jan 5.

DOI:10.1016/j.jinorgbio.2005.11.021

PMID:16403572

Abstract

ATP hydrolysis in the presence of polyoxomolybdates at pH levels of 6, 4, and 2 has been investigated with a help of high pressure liquid chromatography (HPLC) analyses, 31P- and 1H NMR measurements, and isothermal titration calorimetry (ITC). The polyoxomolybdates-induced ATP-hydrolysis proceeded satisfactorily in pH < 6 media at 20 degrees C with an optimum pH level of 4, while it was significantly depressed at low temperature of < or = 5 degrees C. At pH levels of 6 and 4, ADP was a main product, and the involvement of (PO4)2Mo5O15-like ATP-molybdate complex as an intermediate was implied. At pH 2 ATP was decomposed to AMP with small generation of ADP through the formation of the ATP-molybdate complex isostructural with [(O3POPO3)Mo6O18(H2O)4]4- as an intermediate. The ITC result at pH 4 showed an occurrence of two types of the exothermic binding reactions between molybdate and ATP with binding constants (K) of 6.61x10(4) and 9.40x10(3) M(-1) and molar enthalpy values (deltaH) of -6.32x10(4) and -4.73x10(3) J mol(-1), respectively. Together with the results of 1H NMR measurements, it is deduced that the molybdates interact with not only phosphate sites in the ATP side-chain, but also adenine-ring with an accompanying aggregation of molybdates at pH 4.

摘要

借助高压液相色谱（HPLC）分析、³¹P 和 ¹H NMR 测量以及等温滴定量热法（ITC），研究了在 pH 值为 6、4 和 2 的条件下，多金属氧酸盐存在时 ATP 的水解情况。多金属氧酸盐诱导的 ATP 水解在 20℃、pH < 6 的介质中进行得较为顺利，最佳 pH 值为 4，而在≤5℃的低温下显著受到抑制。在 pH 值为 6 和 4 时，ADP 是主要产物，这意味着可能存在(PO₄)₂Mo₅O₁₅样的 ATP - 钼酸盐络合物作为中间体。在 pH 为 2 时，ATP 通过形成与[(O₃POPO₃)Mo₆O₁₈(H₂O)₄]⁴⁻同构的 ATP - 钼酸盐络合物作为中间体，分解为 AMP，并少量生成 ADP。pH 为 4 时的 ITC 结果表明，钼酸盐与 ATP 之间发生了两种放热结合反应，结合常数（K）分别为 6.61×10⁴ 和 9.40×10³ M⁻¹，摩尔焓值（ΔH）分别为 -6.32×10⁴ 和 -4.73×10³ J mol⁻¹。结合 ¹H NMR 测量结果推断，在 pH 为 4 时，钼酸盐不仅与 ATP 侧链中的磷酸位点相互作用，还与腺嘌呤环相互作用，同时伴随着钼酸盐的聚集。