腺苷5'-二磷酸歧化为腺苷5'-三磷酸和腺苷5'-单磷酸的热力学，II. 实验数据

Thermodynamics of the disproportionation of adenosine 5'-diphosphate to adenosine 5'-triphosphate and adenosine 5'-monophosphate, II. Experimental data.

作者信息

Tewari Y B, Goldberg R N, Advani J V

机构信息

Chemical Thermodynamics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.

出版信息

Biophys Chem. 1991 Jul;40(3):263-76. doi: 10.1016/0301-4622(91)80025-m.

DOI:10.1016/0301-4622(91)80025-m

PMID:17014782

Abstract

High-pressure liquid-chromatography and microcalorimetry have been used to determine equilibrium constants and enthalpies of reaction for the disproportionation reaction of adenosine 5'-diphosphate (ADP) to adenosine 5'-triphosphate (ATP) and adenosine 5'-monophosphate (AMP). Adenylate kinase was used to catalyze this reaction. The measurements were carried out over the temperature range 286 to 311 K, at ionic strengths varying from 0.06 to 0.33 mol kg(-1), over the pH range 6.04 to 8.87, and over the pMg range 2.22 to 7.16, where pMg = -log a(Mg2+). The equilibrium model developed by Goldberg and Tewari (see the previous paper in this issue) was used for the analysis of the measurements. Thus, for the reference reaction: 2 ADp(3-) (ao) AMp(2-) (ao)+ ATp- (ao), K degrees = 0.225 +/- 0.010, DeltaG degrees = 3.70 +- 0.11 kJ mol (-1), DeltaH degrees = -1.5 +/- 1. 5 kJ mol (-1), degrees S degrees = -17 +/- 5 J mol(-1)K(-1), and ACP(p) degrees approximately = -46 J mo1l(-1)K(-1) at 298.15 K and 0.1 MPa. These results and the thermodynamic parameters for the auxiliary equilibria in solution have been used to model the thermodynamics of the disproportionation reaction over a wide range of temperature, pH, ionic strength, and magnesium ion morality. Under approximately physiological conditions (311.15 K, pH 6.94, [Mg2+] = 1.35 x 10(-3) mol kg(-1), and I = 0.23 mol kg(-1)) the apparent equilibrium constant (KA' = m(SigmaAMP)m(SigmaATP)/[ m(SigmaADP)]2) for the overall disproportionation reaction is equal to 0.93 +/- 0.02. Thermodynamic data on the disproportionation reaction and literature values for this apparent equilibrium constant in human red blood cells are used to calculate a morality of 1.94 x 10(-4) mol kg(-1) for free magnesium ion in human red blood cells. The results are also discussed in relation to thermochemical cycles and compared with data on the hydrolysis of the guanosine phosphates.

摘要

已使用高压液相色谱法和微量量热法来测定腺苷5'-二磷酸（ADP）歧化为腺苷5'-三磷酸（ATP）和腺苷5'-单磷酸（AMP）反应的平衡常数和反应焓。使用腺苷酸激酶催化该反应。测量在286至311 K的温度范围内、离子强度在0.06至0.33 mol kg⁻¹之间变化、pH范围在6.04至8.87之间以及pMg范围在2.22至7.16之间进行，其中pMg = -log a(Mg²⁺)。由戈德堡和蒂瓦里开发的平衡模型（见本期上一篇论文）用于分析测量结果。因此，对于参考反应：2ADP³⁻(ao)⇌AMP²⁻(ao)+ATP⁻(ao)，在298.15 K和0.1 MPa下，K° = 0.225 ± 0.010，ΔG° = 3.70 ± 0.11 kJ mol⁻¹，ΔH° = -1.5 ± 1.5 kJ mol⁻¹，ΔS° = -17 ± 5 J mol⁻¹K⁻¹，且ACP(p)°约为 -46 J mo⁻¹K⁻¹。这些结果以及溶液中辅助平衡的热力学参数已用于在广泛的温度、pH、离子强度和镁离子摩尔浓度范围内对歧化反应的热力学进行建模。在大约生理条件下（311.15 K，pH 6.94，[Mg²⁺] = 1.35×10⁻³ mol kg⁻¹，且I = 0.23 mol kg⁻¹），总歧化反应的表观平衡常数（KA' = m(ΣAMP)m(ΣATP)/[m(ΣADP)]²）等于0.93 ± 0.02。利用歧化反应的热力学数据和人体红细胞中该表观平衡常数的文献值来计算人体红细胞中游离镁离子的摩尔浓度为1.94×10⁻⁴ mol kg⁻¹。还结合热化学循环对结果进行了讨论，并与鸟苷磷酸水解的数据进行了比较。