The analysis of kinetic data for regulatory enzymes as a function of pH.

A new method is described for the analysis of kinetic data for regulatory enzymes as a function of pH. The method makes use of the limiting hyperbolae predicted by the exponential model for a regulatory enzyme. The pH dependence of the parameters that describe these hyperbolae can be analysed with the Michaelis pH functions to give the pK values of the enzyme-substrate complex and those of the free enzyme in its limiting conformational states. The procedure is illustrated by application to data for the effect of pH on the kinetic properties of aspartate transcarbamylase (carbamoylphosphate: L-aspartate carbamoyltransferase, EC 2.1.3.2).