Mathematical Description of the Enzymatic Activity of Proteins with Ionizable Groups Exhibiting Deviations from the Henderson-Hasselbalch Equation

The ionization equilibrium implied in the calculation of the specific activity is classically described through the Henderson-Hasselbalch equation. An extension for the description of anomalous ionization profiles using the Hill equation is presented in this communication. The proposed framework was applied to the description of the specific enzymatic activity curve as a function of pH of five enzymes presenting different ionization states in their active site. The developed equation improves the description of relative enzymatic curves that deviate from the bell curve predicted by the application of the Henderson-Hasselbalch equation, regardless of the ionization scheme related to the active site.

Automated summary

The study introduces an extension using the Hill equation to describe anomalous ionization profiles, applied to five enzymes with different ionization states. The developed equation improves the description of enzymatic curves deviating from the bell curve predicted by the Henderson-Hasselbalch equation, regardless of the ionization scheme related to the active site.