Exercise 2. Inhibition of Catechol Oxidase Some inhibitors bind to the active si
ID: 142818 • Letter: E
Question
Exercise 2. Inhibition of Catechol Oxidase Some inhibitors bind to the active site of the enzyme and never release from it, and once bound to inhibitor, the enzyme is non-functional. Such inhibitors are called suicide substrates. Other inhibitors bind to the enzyme reversibly, so they may stay bound for a fraction of a second, release, diffuse apart, and then the enzyme can bind something else, either a substrate molecule or another inhibitor. Think about the experiment we are running, and how the specific components are added (enzyme, substrate, and inhibitor) 1. If PTU is a suicide substrate, will tubes 1 and 2 give a similar or a different result? Explain 2. If PTU is a standard competitive inhibitor, will tubes 1 and 2 give a similar or a different result? Page 1 of 11Explanation / Answer
1) If the PTU is a suicidal substrate, the tubes 1 and 2 will give the same result. This is because, PTU will occupy the active site on the enzyme and no further reactions are possible.
2) If PTU is a standard competitive inhibitor, the tubes 1 and 2 will give different results. This is due to the fact that as the concentration of the substrate increases, the inhibitor will leave the active site on enzyme.
3) PTU is a non competitive inhibitor.
4) The inhibitory action of PTU cannot be changed by increasing the concentration of the substrate.
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