Effect of temperature on the creatine kinase equilibrium

Area of Science:

• Biochemistry
• Bioenergetics
• Enzyme kinetics

Background:

• Creatine kinase (ATP:creatine N-phosphotransferase) is crucial for cellular energy homeostasis.
• Understanding the temperature-dependent thermodynamics of creatine kinase is vital for interpreting bioenergetic data.

Purpose of the Study:

• To determine the effect of temperature on the apparent equilibrium constant (K') of the creatine kinase reaction.
• To calculate the standard apparent thermodynamic parameters (enthalpy, entropy, Gibbs energy) of the reaction.

Main Methods:

• The apparent equilibrium constant (K') was measured at various temperatures (5-38°C) under controlled conditions (pH 7.0, 1.0 mM free Mg2+, 0.25 M ionic strength).
• A van't Hoff plot (log10K' vs. 1/T) was used to determine the standard apparent enthalpy (ΔH'°).
• Standard apparent entropy (ΔS'°) and Gibbs energy (ΔG'°) were calculated.

Main Results:

• Apparent K' values ranged from 177 at 38°C to 307 at 5°C.
• The standard apparent enthalpy (ΔH'°) was -11.93 kJ mol⁻¹ (in the direction of ATP formation).
• The standard apparent entropy (ΔS'°) was +4.70 J K⁻¹ mol⁻¹, indicating ΔG'° is primarily enthalpy-driven.

Conclusions:

• Thermodynamic parameters (ΔH'°, ΔS'°) are temperature-independent between 5-38°C for the creatine kinase reaction.
• The calculated thermodynamic data enable bioenergetic investigations across the physiological temperature range.
• This research provides a foundation for understanding creatine kinase function in diverse thermal environments.