Apparent equilibrium constants and calorimetric enthalpies of reaction have been measured for the following enzyme-catalysed biochemical reactions 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 enthalpy, entropy, and Gibbs energy changes for reference reactions involving specific species. Apparent equilibrium constants and standard transformed Gibbs energy changes for these reactions under physiological conditions have also been calculated. The results are discussed in terms of the changes in chemical bonding characteristic of transamination reactions.