An inhibitor is a material that reduces the rate of an enzyme reaction. I have an enzyme catalyzed reaction and I observe that the Vmax is 400Ms1 and the KM is 2.8mM. If I double the amount of enzyme in the reaction the Vmax value also doubles. Explain this observation. When I add a small amount of an inhibitor I observe that the Vmax is now 220M s1 and the KM is 2.8mM. What kind of inhibitor is this? Play The Percentages have an aspartic acid group in the enzyme pepsin. This enzyme works best in the acid f your stomach. What is the percent of the sidechain of aspartic acid that is in it's acidic form at pH 2.65