COMBINATION PLOTS AS GRAPHICAL TOOLS IN THE STUDY OF ENZYME-INHIBITION

Although statistical regression has become the method of choice in the analysis of enzyme kinetics, graphical methods continue to be useful on account of their illustrative capabilities. It is pointed out in this paper that enzyme inhibition data may be presented more efficiently as a single linear plot than the traditional way as a family of lines. This approach has been previously by Hunter and Downes (1945)J.Biol. Chem. 157, 427-446 but has remained neglected. A new version of this type of plot (combined plot) has been devised which is linear for competitive, non-competitive, uncompetitive and linear mixed inhibition and has a characteristic appearance for each type of inhibition behavior. The slopes and intercepts not only indicate directly the dissociation constant but also provide quantitative criteria for the nature of inhibition. This plot should serve as a useful graphical tool in enzyme research as well as in biochemical education.