Studies on Oxalacetate Carboxylyase of Pig Heart Muscle

Oxalacetate carboxylyase was extracted from pig heart muscle and purified about 40 fold by means of acid and heat treatments, salting out and three steps of column chromatography. Some properties of the enzyme were studied by manometric and spectrophotometric measurements. The enzyme activity was optimal at pH 7. Km for oxalacetate was 4.3 × 10^?3 m/liter and the activation energy of the enzyme reaction was 15 kcal/m. The enzyme was activated by certain bivalent cations, among which Mn²⁺ was the most effective. Cu²⁺, Hg²⁺, some metal chelating reagents (EDTA, citrate and Oxalate) and pCMB strongly inhibited the enzyme activity. Inhibition by avidin was not observed, suggesting that biotin was not involved in the reaction as the prosthetic group of the enzyme.