Previous studies with propionyl coenzyme A carboxylase and with phosphoenolpyruvate carboxylase using ‘*O-labeled bicarbonate have indicated that bicarbonate is the reactive species in these fixations of “C02.” We have investigated the species of CO:! in reactions catalyzed by pyruvate carboxylase, P-enolpyruvate carboxykinase, and P-enolpyruvate carboxytransphosphorylase. Since propionyl-CoA c...

A mechanism for regulating the rate of NAD-linked substrate oxidation in isolated liver mitochondria was investigated. Addition of oligomycin and a-ketoglutarate to isolated uncoupled rat liver mitochondria oxidizing an NADlinked substrate such as L( -)-palmitylcarnitine plus L-malate caused an abrupt inhibition of oxygen consumption and of citrate, acetoacetate, and /3-hydroxybutyrate synthesi...

In cultured rat hepatocytes the degradation of phosphoenolpyruvate carboxykinase mRNA might be regulated by protein(s), which by binding to the mRNA alter its stability. The 3'-untranslated region of phosphoenolpyruvate carboxykinase mRNA as a potential target was used to select RNA-binding protein(s) from rat liver by the use of gel retardation assays. A cytosolic protein was isolated, which b...