AN EQUILIBRIUM AND CALORIMETRIC STUDY OF SOME TRANSAMINATION REACTIONS

Apparent equilibrium constants and calorimetric enthalpies of reaction have been measured for the following enzyme-catalysed biochemical rea ctions at the temperature 298.15 K: L-alanine(aq)+ 2-oxoglutarate(aq) = pyruvate(aq)+ L-glutamate(aq); L-tyrosine(aq)+ 2-oxoglutarate(aq)= 4 -hydroxyphenylpyruvate(aq) + L-glutamate(aq); and L-phenylalanine(aq) + 2-oxoglutarate(aq)= phenylpyruvate(aq)+ L-glutamate(aq). The results are used to calculate equilibrium constants and standard molar enthal py, entropy, and Gibbs energy changes for reference reactions involvin g specific species. Apparent equilibrium constants and standard transf ormed Gibbs energy changes for these reactions under physiological con ditions have also been calculated. The results are discussed in terms of the changes in chemical bonding characteristic of transamination re actions. (C) 1998 Academic Press.