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Which of the following statements regarding enzyme inhibition is correct -
A
Competitive inhibition is seen when a substrate competes with an enzyme for binding to an inhibitor protein
B
Non-competitive inhibitors often bind to the enzyme irreversibly
C
Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme
D
Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate
Detailed Solution
A competitive inhibitor closely resembles the substrate in its molecular structure.
It competes with the substrate for the active site of the enzyme; when the inhibitor occupies the active site, the substrate cannot bind and the enzyme action declines.
For example, malonate competes with succinate for the active site of succinic dehydrogenase.
Competitive inhibition can be overcome by increasing the concentration of the substrate.
A non-competitive inhibitor binds at a site other than the active site and changes the shape of the enzyme; adding more substrate does not overcome it.
In the first statement the roles are confused (the substrate does not compete with the enzyme), and the second statement is not a general feature.
So the correct statement is that competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme.
It competes with the substrate for the active site of the enzyme; when the inhibitor occupies the active site, the substrate cannot bind and the enzyme action declines.
For example, malonate competes with succinate for the active site of succinic dehydrogenase.
Competitive inhibition can be overcome by increasing the concentration of the substrate.
A non-competitive inhibitor binds at a site other than the active site and changes the shape of the enzyme; adding more substrate does not overcome it.
In the first statement the roles are confused (the substrate does not compete with the enzyme), and the second statement is not a general feature.
So the correct statement is that competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme.