THE EQUILIBRIUM OF THE REACTION CATALYSED BY CITRATE OXALOACETATE-LYASE

Abstract

A method of preparation and purification of citrate oxaloacetate-lyase (EC 4.1.3.6) from Aerobacter aerogenes is described. The equilibrium of this reaction has been determined at pH 8.4 and 25[degree]. It has been shown that K, i.e. [citrate3]/[oxaloacetateteko2-][acetate-], is 3.08 [plus or minus] 0.72, but that Kapp, i.e. [total citrate]/[total oxaloacetate][total acetate], is markedly affected by the initial concentrations of the reactants and magnesium. The free-energy change during the cleavage of citrate has been calculated and compared with data from other sources. The free energy of hydrolysis of acetyl-CoA has been evaluated from the present data. A detailed knowledge of the interactions of the reactants with metal ions has been shown to be important in the calculation of the equilibrium constant and related thermodynamic functions.