Determine the Michaelis-Menten constant from a graph. Compare the affinities of two enzymes that have different Km values. Explain how a competitive inhibitor works and influence Km and Vmax values.
(a) First of all, we have to determine Vmax by using the graph provided. Try drawing a straight line parallel to the x-axis that is very close to the graph and almost seems to touch it. This is called an asymptote which is essentially a line that a graph approaches, but never intersect. The y-intercept of this line is the Vmax. Now, divide this by two and find that value on the y-axis. Then, find the corresponding x coordinate value based on the y coordinate just found; this will be the Km. (b) If enzyme A’s KM < enzyme B’s KM, then the affinity of enzyme A for the substrate is higher than the affinity of enzyme B.(c) First, let’s remember what a competitive inhibitor is. A competitive inhibitor is a compound that has a similar shape to the enzyme’s substrate that can therefore bind to the active site of the enzyme. This prevents the enzyme from acting on the substrate. It is very important to know that competitive inhibition can be overcome by adding more substrate to the reaction; therefore, increasing the chances of the enzyme and substrate binding. As a result, this alters only the Km, leaving the Vmax the same. Competitive inhibition affects the substrate's ability to bind by binding an inhibitor in place of a substrate, this lowers the affinity of the enzyme for the substrate.
