What experiment would test whether an enzyme is competitive or non-competitive?
I assume you mean whether an enzyme inhibitor is competitive or non-competitive and since I have some spare time here is a little primer to answer the question I assume you’re asking.First you start with your enzyme in a tube (you will need to keep the concentration of enzyme constant for every experiment I am about to describe for this to work). You will perform a kinetic assay to determine the rate of the reaction under a range of substrate concentrations. For each concentration you will get a graph that looks like this:For this graph at each concentration you will determine the slope of the linear portion which is extrapolated in this graph as the dotted red line. Once you have done this for each substrate concentration you will have the reaction rates (in mole product/time) for each concentration also known as the Vo.You will then plot the Vo versus the substrate concentration and you will get a graph which looks as follows:This graph is known as a Michaelis-Menten plot and will give you two important kinetic parameters for your enzyme: Vmax, the maximum velocity of your enzyme and Km, the affinity of your enzyme for the substrate. The Km is the substrate concentration at which the reaction rate is half of Vmax and is reported in units of molarity. The lower the Km, the higher the affinity of your enzyme for its substrate.You will then perform these same experiments in the presence of your inhibitor and you will get a graph as follows:The main differences between a competitive inhibitor and a noncompetitive inhibitor is that the competitive inhibitor will still allow the reaction to reach Vmax, however it will take a higher substrate concentration to do so therefore the Km is increased but the Vmax remains the same. A noncompetitive inhibitor prevents the reaction from ever reaching Vmax and also increases the Km.If you want to get even more technical and precise, you can take the double reciprocal of the Michaelis-Menten equation which turns the hyperbolic plot into a line:This becomes a plot of 1/velocity as a function of 1/[substrate]. The line’s slope will be the ration of Km/Vmax and the y-intercept is 1/Vmax. These plots will change as follows for the three different types of enzyme inhibitors:Signed,A Woman Who Loves Enzymology