Interference by phosphatases in the spectrophotometric assay for phosphoenolpyruvate carboxylase.

A simple and accurate spectrophotometric assay for phosphoenolpyruvate carboxylase activity.

The rate of phosphoenolpyruvate carboxylase activity measured through the conventional coupled assay with malate dehydrogenase is underestimated due to the instability of oxaloacetate, which undergoes partial decarboxylation into pyruvate in the presence of metal ions. The addition of lactate dehydrogenase to the conventional assay allows the reduction of pyruvate formed from oxaloacetate to la...

Title : RNA interference - based suppression of phosphoenolpyruvate carboxylase results in susceptibilty of rapeseed to osmotic stress Running title : Phosphoenolpyruvate carboxylase and water stress tolerance in rapeseed

The Carboxylation of Phosphoenolpyruvate and Pyruvate I. THE ACTIVE SPECIES OF “COz” UTILIZED BY PHOSPHOENOLPYRUVATE

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...

Kinetic measurement of bicarbonate in serum by thiocyanate inhibition of wheat germ phosphoenolpyruvate carboxylase.

We describe a kinetic enzymic method for serum bicarbonate analysis, using wheat germ phosphoenolpyruvate carboxylase (EC 4.1.1.31) coupled through oxaloacetate reduction with NADH in the presence of malate dehydrogenase (EC 1.1.1.37). Inhibition with potassium thiocyanate yielded first-order kinetics with respect to bicarbonate over the concentration range of 0-45 mmol/L. The inhibitor was cho...

Potential importance of metal-ligand interactions in enzyme assays demonstrated with the assay cocktail for phosphoenolpyruvate carboxylase.

Assay cocktail modification such as addition of effector can cause inadvertent changes in the concentration of other metalligand and free species. In some cases, e.g. in the assay for phosphoenolpyruvate carboxylase under a limiting-substrate condition, unintentional changes in substrate concentration are significant and confound an interpretation based solely on the total concentration of each...