31P NMR and isothermal titration calorimetry studies on polyoxomolybdates-catalyzed hydrolysis of ATP.
31P NMR and isothermal titration calorimetry studies on polyoxomolybdates-catalyzed hydrolysis of ATP.
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DOI：
10.1016/j.jinorgbio.2005.11.021
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发表时间：
2006-03
影响因子：
3.9
通讯作者：
E. Ishikawa;T. Yamase
中科院分区：
文献类型：
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作者：
E. Ishikawa;T. Yamase
利用高压液相色谱（HPLC）分析、~（31）P-和~ 1H NMR测量以及等温滴定量热法（ITC）研究了多钼酸盐在pH为6、4和2时对ATP的水解作用。在20°C、pH<6的介质中，多钼酸盐诱导的ATP水解反应能较好地进行，最适pH为4，而在105 °C的低温下，多钼酸盐诱导的ATP水解反应受到显著抑制。在pH值为6和4时，ADP是主要产物，[（PO 4）2 Mo 5 O 15]6-类ATP-ATP络合物作为中间产物参与其中。在pH 2时，ATP分解为AMP，并通过形成与[（O3 POPO 3）Mo 6 O 18（H2O）4]4−同结构的ATP-ATP复合物生成少量ADP。ITC结果表明，在pH为4时，ATP与ATP发生两种类型的放热结合反应，结合常数K分别为6.61× 104和9.40× 103 M − 1，摩尔焓ΔH分别为−6.32× 104和−4.73× 103 Jmol −1.结合~ 1H NMR的测定结果，推测在pH 4时，腺苷酸不仅与ATP侧链上的磷酸位点相互作用，还与腺嘌呤环相互作用，并伴随腺苷酸的聚集。
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- and1H NMR measurements, and isothermal titration calorimetry (ITC). The polyoxomolybdates-induced ATP-hydrolysis proceeded satisfactorily in pH<6 media at 20°C with an optimum pH level of 4, while it was significantly depressed at low temperature of ⩽5°C. At pH levels of 6 and 4, ADP was a main product, and the involvement of [(PO4)2Mo5O15]6−-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 6.61×104and 9.40×103M−1and molar enthalpy values (ΔH) of −6.32×104and −4.73×103Jmol−1, respectively. Together with the results of1H 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.