RELATIONSHIP BETWEEN PYRUVATE CARBOXYLATION AND CITRULLINE SYNTHESIS IN RAT-LIVER MITOCHONDRIA - EFFECT OF AMMONIA AND ENERGY

1. 1. Pyruvate carboxylation and citrulline synthesis were studied in rat liver mitochondria incubated in Slate 4 and State 3 in order to vary the intramitochondrial ATP/ADP ratio. 2. 2. 1 mM NH4Cl diminished the rate of pyruvate carboxylation in the presence and absence of fatty acids. 3. 3. The addition of NH4Cl resulted in a decrease of Vmax value of pyruvate carboxylation but had no effect on the Km value for ATP. 4. 4. In mitochondria incubated in State 4 and State 3 citrulline synthesis resulted in a decrease of pyruvate carboxylation, suggesting a competition for energy between carbamoylphosphate synthase (ammonia) and pyruvate carboxylase. 5. 5. When exogenous ATP was used as an energy source an inhibition of the rate of pyruvate carhoxylation by citrulline synthesis was not observed. © 1979.