ABSTRACT
Drugs can produce pharmacological effects by interacting with active proteins such as enzymes. Enzymes, in fact, constitute the primary site of action for many drugs. Similar to receptor inhibition, enzyme inhibition may also be reversible or irreversible. An irreversible inhibitor dissociates very slowly from its target (enzyme or receptor) because it becomes veiy tightly bound to the active site of the target either covalently or noncovalently. Pharmacologically, irreversible inhibition of enzymes is beneficial when the abnormal activity of a particular enzyme is unnecessary for normal biochemical or physiological functions in the body. The hallmark of competitive inhibition is that the inhibitor can combine with the free enzyme in such a way that it competes with the normal substrate for binding at the same active site. A noncompetitive inhibitor can combine with either free enzyme or the enzyme-substrate complex and consequently interfere with the action of both. Many drugs inhibit the enzymatic hydrolysis of acetylcholine when added to the enzyme-substrate complex.
