Reaction of phosphoenolpyruvate carboxylase with (Z)-3-bromophosphoenolpyruvate and (Z)-3-fluorophosphoenolpyruvate

(Z)-3-Bromophosphoenolpyruvate inactivates phosphoenolpyruvate carboxylase from maize in the presence of HCO3- and either Mg2+ or Mn2+. The inactivation rate follows saturation kinetics. Inactivation is slower in the presence of phospholactate or epoxymaleate, both of which are inhibitors of the enzyme, or dithiothreitol. Inactivation is completely prevented by the presence of lactate dehydrogenase and NADH, and 3-bromolactate is formed during this treatment. If the reaction is conducted by using HC18O3-, the inorganic phosphate produced contains 18O. This and other evidence indicate that phosphoenolpyruvate carboxylase catalyzes conversion of bromophosphoenolpyruvate into bromopyruvate by way of the usual carboxyphosphate-enolate intermediate, and bromopyruvate is the species responsible for enzyme inactivation. (Z)-3-fluorophosphoenolpyruvate is transformed by the enzyme into a 6:1 mixture of 3-fluoropyruvate and 3-fluorooxalacetate, presumably by the same mechanism. The enzyme is not inactivated during this treatment