Ammonia formation from some amino acids by human term placental mitochondria

Abstract

The formation of ammonia from glutamine, glutamate, and branched-chain amino acids by human term placental mitochondria has been investigated. It has been shown that ammonia production from glutamine and glutamate was stimulated by NAD and ADP and was inhibited by oxoglutarate. Oxoglutarate substantially stimulated ammonia production from branched-chain amino acids. Ammonia production from branched-chain amino acids was inhibited by aminooxyacetate. The formation of lactate was observed during incubation of human term placental mitochondria with dicarboxylic Krebs-cycle intermediates and glutamate in the presence of lactate dehydrogenase. These results suggest that human term placental mitochondria are able to deaminate some amino acids and that the resulting carbon skeleton from glutamate could be converted to Krebs-cycle intermediates. The physiological significance of glutamate metabolism in human term placenta is discussed.