Tewari Y B, Steckler D K, Goldberg R N, Gitomer W L
Chemical Thermodynamics Division, National Bureau of Standards, Gaithersburg, Maryland 20899.
J Biol Chem. 1988 Mar 15;263(8):3670-5.
Thermodynamics of the enzyme-catalyzed (alkaline phosphatase, EC 3.1.3.1) hydrolysis of glucose 6-phosphate, mannose 6-phosphate, fructose 6-phosphate, ribose 5-phosphate, and ribulose 5-phosphate have been investigated using microcalorimetry and, for the hydrolysis of fructose 6-phosphate, chemical equilibrium measurements. Results of these measurements for the processes sugar phosphate2- (aqueous) + H2O (liquid) = sugar (aqueous) + HPO2++-(4) (aqueous) at 25 degrees C follow: delta Ho = 0.91 +/- 0.35 kJ.mol-1 and delta Cop = -48 +/- 18 J.mol-1.K-1 for glucose 6-phosphate; delta Ho = 1.40 +/- 0.31 kJ.mol-1 and delta Cop = -46 +/- 11 J.mol-1.dK-1 for mannose 6-phosphate; delta Go = -13.70 +/- 0.28 kJ.mol-1, delta Ho = -7.61 +/- 0.68 kJ.mol-1, and delta Cop = -28 +/- 42 J.mol-1.K-1 for fructose 6-phosphate; delta Ho = -5.69 +/- 0.52 kJ.mol-1 and delta Cop = -63 +/- 37 J.mol-1.K-1 for ribose 5-phosphate; and delta Ho = -12.43 +/- 0.45 kJ.mol-1 and delta Cop = -84 +/- 30 J.mol-1.K-1 for the hydrolysis of ribulose 5-phosphate. The standard state is the hypothetical ideal solution of unit molality. Estimates are made for the equilibrium constants for the hydrolysis of ribose and ribulose 5-phosphates. The effects of pH, magnesium ion concentration, and ionic strength on the thermodynamics of these reactions are considered.
已使用微量量热法对葡萄糖 6 - 磷酸、甘露糖 6 - 磷酸、果糖 6 - 磷酸、核糖 5 - 磷酸和核酮糖 5 - 磷酸的酶催化（碱性磷酸酶，EC 3.1.3.1）水解的热力学进行了研究，对于果糖 6 - 磷酸的水解还进行了化学平衡测量。在 25℃下，这些糖磷酸根离子2 - （水溶液） + H₂O（液体） = 糖（水溶液） + HPO₄²⁻（水溶液）过程的测量结果如下：葡萄糖 6 - 磷酸：ΔHₒ = 0.91 ± 0.35 kJ·mol⁻¹，ΔCₒₚ = -48 ± 18 J·mol⁻¹·K⁻¹；甘露糖 6 - 磷酸：ΔHₒ = 1.40 ± 0.31 kJ·mol⁻¹，ΔCₒₚ = -46 ± 11 J·mol⁻¹·K⁻¹；果糖 6 - 磷酸：ΔGₒ = -13.70 ± 0.28 kJ·mol⁻¹，ΔHₒ = -7.61 ± 0.68 kJ·mol⁻¹，ΔCₒₚ = -28 ± 42 J·mol⁻¹·K⁻¹；核糖 5 - 磷酸：ΔHₒ = -5.69 ± 0.52 kJ·mol⁻¹，ΔCₒₚ = -63 ± 37 J·mol⁻¹·K⁻¹；核酮糖 5 - 磷酸水解：ΔHₒ = -12.43 ± 0.45 kJ·mol⁻¹，ΔCₒₚ = -84 ± 30 J·mol⁻¹·K⁻¹。标准态是假设的单位质量摩尔浓度的理想溶液。对核糖和核酮糖 5 - 磷酸水解的平衡常数进行了估算。考虑了 pH、镁离子浓度和离子强度对这些反应热力学的影响。
