 Decarboxylating the beta-keto acid of oxaloacetate affords the necessary free energy to pump sodium ions across the lipid bilayer.The resulting sodium gradient drives the synthesis of ATP, solute transport, and motility.The overall reaction catalyzed by the pump is the exchange of two intracellular Na+ ions for one extra cellular H+ ion; the reaction is initiated by the enzyme-catalyzed decarboxylation of oxaloacetate in the carboxyltransferase domain of the alpha subunit, yielding pyruvate and carboxybiotin.