Proton uptake accompanies formation of the ternary complex of citrate synthase, oxaloacetate and the transition-state analog inhibitor, carboxymethyl-CoA; evidence that a neutral enol is the activated form of acetyl-CoA in the citrate synthase reaction

Citrate synthase complexes with the transition-state analog inhibitor, carboxymethyl-CoA, are similar to those with the activated form of acetyl-CoA. The X-ray structure of the ternary complex of the enzyme, oxaloacetate and carboxymethyl-CoA has been used as the basis for a proposal that a neutral enol of acetyl-CoA is that activated form.