GLUTAMATE OXIDATION IN RAT-LIVER HOMOGENATE

1. In rat-liver homogenate ammonia can be produced from adenine nucleotides by deamination of AMP when no oxidizable substrate is added. Glutamate prevents ammonia formation by lowering the AMP level and by removal of ammonia as glutamine. 2. The time course of glutamate oxidation in rat-liver homogenates is biphasic. In the first 10 min of the reaction aspartate production and deamination of glutamate are equal. In the 10-30-min period ammonia formation from glutamate declines, while the aspartate formation is correspondingly stimulated. 3. Ammonia formed by deamination of glutamate cannot be used for the synthesis of citrulline under the conditions used, due to its efficient removal as glutamine. Aspartate formed via the transamination pathway can be used as nitrogen donor for arginine synthesis from citrulline. This causes a stimulation of the transamination pathway. 4. The factors influencing the pathway of glutamate oxidation in rat-liver homogenate are discussed in relation to the metabolism of nitrogen in vivo. © 1969.