GraphPad Curve Fitting Guide

Comparing models of enzyme inhibition

Comparing models of enzyme inhibition

Previous topic Next topic No expanding text in this topic  

Comparing models of enzyme inhibition

Previous topic Next topic JavaScript is required for expanding text JavaScript is required for the print function Mail us feedback on this topic!  

Comparing the fits of the different enzyme inhibition models requires thinking both about enzyme mechanism and about statistics. Some notes:

The mixed model generalizes competitive, noncompetitive and uncompetitive. Each of those three models are special cases of the mixed-model.

Comparing R2 is an easy way to compare fits, but not a very good method.

Comparing the adjusted R2 is a better way to compare fits. To do this, you need to ask for reporting of adjusted R2 in the parameters dialog. But this is not a rigorous way to compare models.

Prism can compare models using two rigorous approaches, the extra sum-of-squares F test and the AICc approach.

The extra sum-of-squares F test is only valid when one model is a special case of (is nested within) the other model. The mixed model is a general equation that includes competitive, uncompetitive and noncompetitive inhibition as special cases, so it is OK to compare the mixed model with any of the other three by F test.  The competitive model is a special case of the uncompetitive or noncompetitive modes, so you can compare the competitive model with either uncompetitive or noncompetitive models by F test. The uncompetitive and noncompetitive models are not nested so cannot be compared by F test.