An efficient method for the determination of K m values for HCO 3 (-) of phosphoenolpyruvate carboxylase.

One of the most serious problems in obtaining estimates of the K m values for HCO 3 (-) of phosphoenolpyruvate carboxylase (PEPCase; EC 4.1.1.31) by measurement of initial rates at varying HCO 3 (-) is the impossibility of completely excluding any contaminating HCO 3 (-) . A method is proposed which has no need for the careful control of HCO 3 (-) /CO2 contamination. The kinetic data are obtained by the evaluation of progress curves of HCO 3 (-) consumption. The method is discussed and the K m values for HCO 3 (-) of PEPCase from several C4-species are presented.