Final answer:
An irreversible inhibitor binds covalently to an enzyme's active site, inactivating it permanently, in contrast to reversible inhibitors which form non-covalent, potentially competitive or noncompetitive interactions.
Step-by-step explanation:
The type of inhibitor that binds covalently to an amino acid positioned in the active site of an enzyme is known as an irreversible inhibitor. This inhibitor inactivates the enzyme by forming a covalent bond with a specific group within the active site, often with amino acid side chains that possess nucleophilic groups such as serine, threonine, or cysteine. These interactions are typically permanent, meaning that the enzyme cannot regain its function without being regenerated or synthesized anew.
Reversible inhibitors, on the other hand, form non-covalent interactions with enzymes and include competitive and noncompetitive inhibitors. Competitive inhibitors resemble the substrate and compete for the active site, while noncompetitive inhibitors bind to another part of the enzyme, potentially causing a conformational change that reduces the enzyme's activity.
It is essential to understand the interactions between inhibitors and enzymes to design drugs that can modulate enzyme activity effectively. Amino acids such as serine, threonine, and cysteine in the active site are common targets for covalent inhibitors in drug design.