Thermodynamics of hexokinase catalyzed reactions. II. Measurement and calculation of enthalpies of reaction as a function of magnesium ion concentration.
Enthalpies of phosphorylation of glucose by adenosine 5'-triphosphate have been measured as a function of concentrations of magnesium chloride in TRIS/TRIS-HCl buffer in the pH range 8.64 to 8.98. These measurements are compared with the results of calculations of these enthalpies that use a coupled equilibrium formalism with equilibrium data and enthalpy values selected from the literature. The experimental results span the range of magnesium ion concentrations 1 X 10(-6) to 0.3 mol alpha-1 and show a total variation in the enthalpy of reaction of almost 10 kJ mol-1, with the most exothermic reaction occurring at a magnesium ion concentration of 6.0 X 10(-4) mol alpha-1. The calculated enthalpies of reaction, except for the magnesium ion concentration range 4 X 10(-6) to 5 X 10(-4) mol alpha-1, are, within estimated uncertainty intervals (0.8 to 10.2 kJ mol-1), in agreement with the measured values.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D002151:Calorimetry; D005947:Glucose / Q000494:pharmacology; D006593:Hexokinase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D008433:Mathematics; D009994:Osmolar Concentration; D013816:Thermodynamics
D000255:Adenosine Triphosphate; D006593:Hexokinase; D008274:Magnesium; D005947:Glucose