3.8. Enzyme Inhibition/Inhibitor and Types

Enzyme Inhibition/Inhibitor:

• Blocking an enzyme's activity by chemical molecules which resemble or mimic a particular enzymes substrate(s) is called Enzyme Inhibition and the mole is said to be an Inhibitor.  Therefore, many therapeutic drugs are some type of enzyme inhibitor.
• Molecules that bind to enzymes and increase their activity are called Enzyme Activators.
• The binding of an inhibitor can stop a substrate from entering the enzyme's active site and/or hinder the enzyme from catalysing its reaction.
• The modes and types of inhibitors have been classified by their kinetic activities and sites of actions.

Types of Inhibition

• Reversible Inhibition: reversible inhibitors bind non-covalently (hydrogen bonds, hydrophobic interactions and ionic bonds) and different types of inhibition are produced depending on whether these inhibitors bind the enzyme, the enzyme-substrate complex, or both.
• Irreversible Inhibition: Irreversible inhibitors usually react with the enzyme and change it chemically. These inhibitors modify key amino acid residues needed for enzymatic activity.
• Enzyme inhibitors also occur naturally and are involved in the regulation of metabolism.

Types of Reversible Inhibition:
(I) Competitive, (II) Non-Competitive, (III) Uncompetitive, and (IV) Mixed Inhibition.

3.8.1. Reversible Enzyme Inhibition