Kinetic Studies on Na+/K+-ATPase by Using Thermokinetic Method

• 来源期刊: 中国化学（英文版）
• 学科: 化学
• 年，卷（期）: 2004,（3）
• 页码范围: 252-255
• 页数: 4页
• 分类号: O6
• 语种: 英文

摘要

Na+/K+-ATPase (EC 3.6.1.3) is an important membrane-bound enzyme. By using microcalorimetry, the thermokinetic method was developed to kinetic studies on Na+/K+-ATPase for the first time. Compared with other ones, the method provided accurate measurements of not only thermodynamic data but also the kinetic data. At 310.15 K and pH＝7.4, the molar reaction enthalpy ΔrHm was measured as (-40.408±1.9) kJ·mol-1. The Michaelis constant Km was determined to be (0.479±0.020)×10-3 mol·L-1 and consistent with literature figure which is about 0.5×10-3 mol·L-1. The maximum velocity Vmax obtained was (0.681±0.026) μmol Pi·min-1·mg protein-1. All of the data have good repeatability and self-consistency. The reliability of thermokinetic method was verified by the experimental results and further confirmed by colorimetric studies. Moreover, the effect of enzyme pre-dilution on its activities was also investigated.