Question

Phosphoglycerate kinase is an important enzyme in the glycolysis. The conversion of 1,3-Bisphosphoglycerate reacts under standard conditions with release of 18,8 kJ pr mol. Hydrolysis of adenosine triphosphate is spontaneous under liberation of 30,4 kJ/mol.
a) Write the complete reaction and calculate ΔG’ for the reaction occurring at 37 °C and pH 7, when it is known that the concentration of adenosine triphosphate, adenosine diphosphate, glycerate-3-phosphate and 1,3-bisphosphoglycerate is 1.25mM, 0.1mM, 1.0 mM and 1μM, respectively.
b) Calculate the ratio between glycerate-3-phosphate and 1,3-bisphosphoglycerate at equilibrium.
Use the same temperature, pH and levels of ATP and ADP as given in question a

Answer 1

1,3- bisphosphoglycerate +   H+                                          3-phosphoglycerate        ΔG0 = -18.8 kJ/mol

ADP       + pi                                                                              ATP                                                 ΔG0 = 30.4 kJ/mol

ΔG0 of the reaction = 30.4 kJ/mol -18.8 kJ/mol = 11.6 kJ/mol

ΔG’ = ΔG0 + RT ln Keq

Keq= (ATP) (3-phosphoglycerate )       

          (ADP) (1,3- bisphosphoglycerate )

a) Write the complete reaction and calculate ΔG’ for the reaction occurring at 37 °C and pH 7, when it is known that the concentration of adenosine triphosphate, adenosine diphosphate, glycerate-3-phosphate and 1,3-bisphosphoglycerate is 1.25mM, 0.1mM, 1.0 mM and 1μM, respectively.

ΔG’ = ΔG0 + RT ln Keq

       = 11.6 + 8.3145 X 310 ln ( 0.0125)

       = - 4893.6 KJ/mol