Kinetic studies of citrate synthase from rat kidney and rat brain.

Crystalline citrate synthase (citrate oxalacetate lyase (coenzyme A-acetylating) EC 4.1.3.7) has been prepared from rat kidney and rat brain. These enzymes are homogeneous as judged by acrylamide gel electrophoresis, and immunologically identical with the rat heart citrate synthase. Steady state kinetic studies including product inhibition experiments indicate that the substrates are added in a random order, the products come off in random order, and that two dead end complexes are formed. When acetyl-CoA concentrations are varied over wide range, a nonlinear Lineweaver-Burk plot is obtained suggesting apparent substrate activation. One interpretation of this observation is that some cooperativity exists between two sites on the enzyme.