Thermodynamic bookkeeping: a reinvestigation of proton and dicarboxylic acid binding to aspartate aminotransferase.
A reinvestigation of the effects of pH and salt concentration on the proton and dicarboxylic acid dissociation constants of pig heart aspartate aminotransferase shows that both anions and cations were involved concomitantly, both as stoichiometric reactants and bioenergetically. Equations are presented which can be used experimentally, to determine the numbers of salt ions (their thermodynamic stoichiometries) involved in biochemical equilibria such as proton and ligand dissociations from macromolecules. These equations were used to reinvestigate the effects of salts on the chromophoric pKa of the enzyme prosthetic group, the interaction of the enzyme with dicarboxylic acids, and the overall equilibrium for the transamination half-reaction.
Jenkins
W T
WT
Department of Chemistry, Indiana University, Bloomington 47405.
D001219:Aspartate Aminotransferases / Q000378:metabolism*; D003998:Dicarboxylic Acids / Q000378:metabolism*; D004734:Energy Metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D011485:Protein Binding; D011522:Protons; D012492:Salts / Q000494:pharmacology; D013816:Thermodynamics
D003998:Dicarboxylic Acids; D011522:Protons; D012492:Salts; D001219:Aspartate Aminotransferases