Thermodynamic study of the hydrolysis of L-glutamine to (L-glutamate plus ammonia) and of L-asparagine to (L-aspartate plus ammonia)

Calorimetric enthalpies of reaction have been measured for the following en zyme-catalysed reactions: L-glutamine(aq) + H2O(1) = L-glutamate(aq) + ammonia(aq), L-asparagine(aq) + H2O(1) = L-aspartate(aq) + ammonia(aq). An equilibrium model that accounted for the multiplicity of ionic forms of the reactants and products was used to calculate standard molar enthalpies for reference reactions involving specific species. Values of equilibrium c onstants for the reference reactions were obtained using results from the l iterature in thermochemical cycle calculations. The thermodynamic results a re discussed in relation to the structural changes involved in these reacti ons. (C) 2000 Academic Press.