Question

Inhibition of acetylcholine by DFP(diisopropyl Fluro-phosphate) is
A.Competitive inhibition
B.Non- competitive inhibition
C.Non-competitive irreversible inhibition
D.Allosteric inhibition

Answer 1

Hint: In non-competitive inhibition, the inhibitor competes with the substrate for the active site of the enzyme. It can be reversible or irreversible whereas Competitive inhibition is reversible.

Complete answer:
In non-competitive inhibition, the inhibitor has no structural similarity with the substrate.
It forms a complex with the enzymes at a place other than active sites.
This inhibition may be reversible or irreversible. Commonly it is irreversible e.g. cyanide inhibits the activity of cytochrome oxidase by combining with copper, iron. ATP synthesis stops.
Diisopropyl fluorophosphate(DFP) is a nerve gas that combines with the hydroxyl group of serine of enzyme acetylcholinesterase.
Working of malathion, parathion, and many other insecticides based on this mechanism.

So, the correct answer is option C. Non-competitive irreversible inhibition.

Note:In competitive inhibition,
It is reversible. When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as a competitive inhibitor. Inhibitor competes with the substrate for the binding site on the enzyme, due to its structural similarity.
Therefore, the substrate cannot bind and the enzyme action declines due to binding of the inhibitor with the active site of the enzyme. This inhibition gives evidence for the lock and key hypothesis of enzyme action.
Allosteric inhibition occurs in allosteric enzymes, where both allosteric and active sites are present.