A new plot for multiple enzyme inhibition.

A new graphical method is described for analyzing the results of multiple inhibition experiments. It is applicable to either single- or multi-substrate enzyme systems obeying Michaelis-Menten kinetics and is valid irrespective of the type of inhibition (competitive, noncompetitive, uncompetitive, mixed). According to this method, mutually exclusive inhibitor binding gives rise to lines that converge on the vertical axis, whereas mutually nonexclusive inhibitors yield lines that intersect to the left of the vertical axis. It has been pointed out that the inhibitor interaction factor can be determined directly from multiple inhibition experiments only if at least one of the inhibitors is noncompetitive. When this is the case, the present plot provides a very simple way of determining the inhibitor interaction factor from the coordinates of the intersection point.