Question

How would a competitive, irreversible inhibitor affect an enzyme? Please explain in detail.

Answer 1

Answer-

Effects of Inhibitors on Enzyme Activity

Enzyme inhibitors are substances which alter the catalytic action of the enzyme and consequently slow down, or in some cases, stop catalysis. There are three common types of enzyme inhibition - competitive, non-competitive and substrate inhibition.

Competitive inhibition occurs when the substrate and a substance resembling the substrate are both added to the enzyme. A theory called the "lock-key theory" of enzyme catalysts can be used to explain why inhibition occurs

The lock and key theory utilizes the concept of an "active site." The concept holds that one particular portion of the enzyme surface has a strong affinity for the substrate. The substrate is held in such a way that its conversion to the reaction products is more favorable. If we consider the enzyme as the lock and the substrate the key. The key is inserted in the lock, is turned, and the door is opened and the reaction proceeds. However, when an inhibitor which resembles the substrate is present, it will compete with the substrate for the position in the enzyme lock. When the inhibitor wins, it gains the lock position but is unable to open the lock. Hence, the observed reaction is slowed down because some of the available enzyme sites are occupied by the inhibitor. If a dissimilar substance which does not fit the site is present, the enzyme rejects it, accepts the substrate, and the reaction proceeds normally.

Irreversible inhibitor affects on enzyme-

An irreversible inhibitor will bind to an enzyme so that no other enzyme-substrate complexes can form. It will bind to the enzyme using a covalent bond at the active site which therefore makes the enzyme denatured. An example of an irreversible inhibitor is diisopropyl fluorophosphate which is present in nerve gas. It binds to the enzyme and stops nerve impulses being transmitted. An example of where we use irreversible inhibitors in medicine is penicillin. Penicillin works by inhibiting the activity of the enzyme responsible for the creation of the bacterial cell wall. This means that water can enter the bacterial cell, causing it to swell, burst and die termed lysis.